RESUMO
BACKGROUND: Iron sucrose (FeS) administration induces a state of renal preconditioning, protecting against selected forms of acute kidney injury (AKI). Recent evidence suggests that recombinant hepcidin also mitigates acute renal damage. Hence the goals of this study were to determine whether a new proprietary FeS formulation ('RBT-3') can acutely activate the hepcidin (HAMP1) gene in humans, raising plasma and renal hepcidin concentrations; assess whether the kidney participates in this posited RBT-3-hepcidin generation response; test whether RBT-3 can mitigate a clinically relevant AKI model (experimental cisplatin toxicity) and explore whether mechanisms in addition to hepcidin generation are operative in RBT-3's cytoprotective effects. METHODS: Healthy human volunteers (n = 9) and subjects with Stages 3-4 CKD (n = 9) received 120, 240 or 360 mg of RBT-3 (intravenously over 2 h). Plasma and urine samples were collected and assayed for hepcidin levels (0-72 h post-RBT-3 injection). In complementary mouse experiments, RBT-3 effects on hepatic versus renal hepcidin (HAMP1) messenger RNA (mRNA) and protein levels were compared. RBT-3's impact on the mouse Nrf2 pathway and on experimental cisplatin nephrotoxicity was assessed. Direct effects of exogenous hepcidin on in vivo and in vitro (HK-2 cells) cisplatin toxicity were also tested. RESULTS: RBT-3 induced rapid, dose-dependent and comparable plasma hepcidin increases in both healthy volunteers and chronic kidney disease subjects (â¼15 times baseline within 24 h). Human kidney hepcidin exposure was confirmed by 4-fold urinary hepcidin increases. RBT-3 up-regulated mouse hepcidin mRNA, but much more so in kidney (>25 times) versus liver (â¼2 times). RBT-3 also activated kidney Nrf2 [increased Nrf2 nuclear binding; increased Nrf2-responsive gene mRNAs: heme oxygenase-1, sulfiredoxin-1, glutamate-cysteine ligase catalytic subunit and NAD(P)H quinone dehydrogenase 1]. RBT-3 preconditioning (18 h time lapse) markedly attenuated experimental cisplatin nephrotoxicity (â¼50% blood urea nitrogen/creatinine decrements), in part by reducing renal cisplatin uptake by 40%. Exogenous hepcidin (without RBT-3) treatment conferred protection against mild in vivo (but not in vitro) cisplatin toxicity. CONCLUSIONS: RBT-3 acutely and dramatically up-regulates cytoprotective hepcidin production, increasing renal hepcidin levels. However, additional cytoprotective mechanisms are activated by RBT-3 (e.g. Nrf2 activation; reduced cisplatin uptake). Thus RBT-3-induced preconditioning likely confers renal resistance to cisplatin via an interplay of multiple cytoprotective activities.
Assuntos
Cisplatino/toxicidade , Resistência a Medicamentos/efeitos dos fármacos , Óxido de Ferro Sacarado/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Hepcidinas/metabolismo , Rim/metabolismo , Fígado/metabolismo , Insuficiência Renal Crônica/metabolismo , Idoso , Animais , Antineoplásicos/toxicidade , Estudos de Casos e Controles , Feminino , Hepcidinas/genética , Humanos , Rim/efeitos dos fármacos , Fígado/efeitos dos fármacos , Masculino , Camundongos , Pessoa de Meia-Idade , Insuficiência Renal Crônica/tratamento farmacológico , Insuficiência Renal Crônica/patologiaRESUMO
The cyclin kinase inhibitor p21 is acutely upregulated during acute kidney injury (AKI) and exerts cytoprotective effects. A proposed mechanism is oxidant stress-induced activation of p53, the dominant p21 transcription factor. Glycerol-induced rhabdomyolysis induces profound renal oxidant stress. Hence, we studied this AKI model to determine whether p53 activation corresponds with p21 gene induction and/or whether alternative mechanism(s) might be involved. CD-1 mice were subjected to glycerol-induced AKI. After 4 or 18 h, plasma, urinary, and renal cortical p21 protein and mRNA levels were assessed. Renal p53 activation was gauged by measurement of both total and activated (Ser15-phosphorylated) p53 and p53 mRNA levels. Glycerol evoked acute, progressive increases in renal cortical p21 mRNA and protein levels. Corresponding plasma (~25-fold) and urinary (~75-fold) p21 elevations were also observed. Renal cortical ratio of total to phosphorylated (Ser15) p53 rose three- to fourfold. However, the p53 inhibitor pifithrin-α failed to block glycerol-induced p21 gene induction, suggesting that an alternative p21 activator might also be at play. To this end, it was established that glycerol-induced AKI 1) dramatically increased plasma (~5-fold) and urinary (~75-fold) cortisol levels, 2) the glucocorticoid receptor antagonist mifepristone blocked glycerol-induced p21 mRNA and protein accumulation, and 3) dexamethasone or cortisol injections markedly increased p21 protein and mRNA in both normal and glycerol-treated mice, although no discernible p53 protein or mRNA increases were observed. We conclude that AKI-induced "systemic stress" markedly increases plasma and urinary cortisol, which can then activate renal p21 gene expression, at least in part, via a glucocorticoid receptor-dependent signaling pathway. Discernible renal cortical p53 increases are not required for this dexamethasone-mediated p21 response.
Assuntos
Injúria Renal Aguda/metabolismo , Inibidor de Quinase Dependente de Ciclina p21/biossíntese , Glucocorticoides/metabolismo , Transdução de Sinais , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/fisiopatologia , Animais , Benzotiazóis/uso terapêutico , Dexametasona/uso terapêutico , Glicerol , Antagonistas de Hormônios/uso terapêutico , Hidrocortisona/sangue , Hidrocortisona/uso terapêutico , Hidrocortisona/urina , Córtex Renal/metabolismo , Masculino , Camundongos , Mifepristona/uso terapêutico , Tolueno/análogos & derivados , Tolueno/uso terapêutico , Proteína Supressora de Tumor p53/antagonistas & inibidores , Proteína Supressora de Tumor p53/metabolismo , Regulação para CimaRESUMO
Experimental data suggest that iron sucrose (FeS) injection, used either alone or in combination with other prooxidants, can induce "renal preconditioning," in part by upregulating cytoprotective ferritin levels. However, the rapidity, degree, composition (heavy vs. light chain), and renal ferritin changes after FeS administration in humans remain to be defined. To address these issues, healthy human volunteers (n = 9) and patients with stage 3-4 chronic kidney disease(n = 9) were injected once with FeS (120, 240, or 360 mg). Plasma ferritin was measured from 0 to 8 days postinjection as an overall index of ferritin generation. Urinary ferritin served as a "biomarker" of renal ferritin production. FeS induced rapid (≤2 h), dose-dependent, plasma ferritin increases in all study participants, peaking at approximately three to five times baseline within 24-48 h. Significant urinary ferritin increases (~3 times), without dose-dependent increases in albuminuria, neutrophil gelatinase-associated lipocalin, or N-acetyl-ß-d-glucosaminidase excretion, were observed. Western blot analysis with ferritin heavy chain (Fhc)- and light chain (Flc)-specific antibodies demonstrated that FeS raised plasma Flc but not Fhc levels. Conversely, FeS increased both Fhc and Flc in urine. To assess sites of FeS-induced ferritin generation, organs from FeS-treated mice were probed for Fhc, Flc, and their mRNAs. FeS predominantly raised hepatic Flc. Conversely, marked Fhc and Flc elevations developed in the kidney and spleen. No cardiopulmonary ferritin increases occurred. Ferritin mRNAs remained unchanged throughout, implying posttranscriptional ferritin production. We conclude that FeS induces rapid, dramatic, and differential Fhc and Flc upregulation in organs. Renal Fhc and Flc increases, in the absence of nephrotoxicity, suggest potential FeS utility as a clinical renal "preconditioning" agent.
Assuntos
Óxido de Ferro Sacarado/farmacologia , Ferritinas/biossíntese , Precondicionamento Isquêmico , Rim/efeitos dos fármacos , Injúria Renal Aguda/prevenção & controle , Adulto , Idoso , Animais , Biomarcadores/urina , Feminino , Óxido de Ferro Sacarado/administração & dosagem , Óxido de Ferro Sacarado/efeitos adversos , Ferritinas/sangue , Ferritinas/urina , Voluntários Saudáveis , Humanos , Infusões Parenterais , Rim/metabolismo , Nefropatias/induzido quimicamente , Nefropatias/patologia , Masculino , Camundongos , Pessoa de Meia-Idade , RNA Mensageiro/biossíntese , Insuficiência Renal Crônica/metabolismo , Baço/metabolismoRESUMO
BACKGROUND: Recent clinical data support the utility/superiority of a new AKI biomarker ("NephroCheck"), the arithmetic product of urinary TIMP × IGFBP7 concentrations. However, the pathophysiologic basis for its utility remains ill defined. METHODS: To clarify this issue, CD-1 mice were subjected to either nephrotoxic (glycerol, maleate) or ischemic AKI. Urinary TIMP2/IGFBP7 concentrations were determined at 4 and 18 hours postinjury and compared with urinary albumin levels. Gene transcription was assessed by measuring renal cortical and/or medullary TIMP2/IGFBP7 mRNAs (4 and 18 hours after AKI induction). For comparison, the mRNAs of three renal "stress" biomarkers (NGAL, heme oxygenase 1, and p21) were assessed. Renal cortical TIMP2/IGFBP7 protein was gauged by ELISA. Proximal tubule-specific TIMP2/IGFBP7 was assessed by immunohistochemistry. RESULTS: Each AKI model induced prompt (4 hours) and marked urinary TIMP2/IGFBP7 increases without an increase in renal cortical concentrations. Furthermore, TIMP2/IGFBP7 mRNAs remained at normal levels. Endotoxemia also failed to increase TIMP2/IGFBP7 mRNAs. In contrast, each AKI model provoked massive NGAL, HO-1, and p21 mRNA increases, confirming that a renal "stress response" had occurred. Urinary albumin rose up to 100-fold and strongly correlated (r=0.87-0.91) with urinary TIMP2/IGFBP7 concentrations. Immunohistochemistry showed progressive TIMP2/IGFBP7 losses from injured proximal tubule cells. Competitive inhibition of endocytic protein reabsorption in normal mice tripled urinary TIMP2/IGFBP7 levels, confirming this pathway's role in determining urinary excretion. CONCLUSIONS: AKI-induced urinary TIMP2/IGFBP7 elevations are not due to stress-induced gene transcription. Rather, increased filtration, decreased tubule reabsorption, and proximal tubule cell TIMP2/IGFBP7 urinary leakage seem to be the most likely mechanisms.
Assuntos
Injúria Renal Aguda/metabolismo , Injúria Renal Aguda/urina , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/urina , Túbulos Renais Proximais/metabolismo , Inibidor Tecidual de Metaloproteinase-2/urina , Injúria Renal Aguda/patologia , Animais , Biomarcadores/urina , Biópsia por Agulha , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática/métodos , Imuno-Histoquímica , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos , Distribuição Aleatória , Sensibilidade e EspecificidadeRESUMO
p21 is upregulated in renal tubules in response to acute kidney injury ( AKI). and localizes in the nucleus, where it induces cell cycle arrest (CCA). These events can mitigate early injury but can also facilitate the onset of the degenerative cell senescence/"aging" process. Hence, we asked the following: 1) can AKI-induced p21 upregulation be gauged by plasma and/or urinary p21 assay; 2) might p21 serve as an AKI/CCA biomarker; and 3) does p21 accumulate during normal renal aging, and might plasma p21 reflect this process? Mice were subjected to either ischemia-reperfusion (I/R) or nephotoxic (maleate) AKI. Renal cortical p21 expression (protein, mRNA) was assessed 2-18 h later and contrasted with plasma/urine p21 concentrations (ELISA). p21 mRNA/protein levels were also measured in aging mice (2, 12, 24 mo). AKI induced marked, progressive, increases in renal cortical p21 mRNA and protein levels. These changes were marked by acute (within 2-4 h) and profound increases (up to 200×) in both plasma and urine p21 concentrations. Renal I/R also activated p21 gene expression in extrarenal organs (heart, brain), consistent with so-called "organ cross talk". p21 efflux from damaged cells was confirmed with studies of hypoxia-injured, isolated proximal tubules. Aging was associated with progressive renal cortical p21 expression, which correlated ( r, 0.83) with rising plasma p21 concentrations. We concluded that 1) during AKI, renal p21 increases can be gauged by either plasma or urine p21 assay, serving as potentially useful AKI/CCA biomarkers; 2) AKI can activate p21 in extrarenal organs; and 3) plasma p21 levels may provide an index of the renal/systemic aging process.
Assuntos
Injúria Renal Aguda/sangue , Injúria Renal Aguda/urina , Envelhecimento/sangue , Envelhecimento/urina , Inibidor de Quinase Dependente de Ciclina p21/sangue , Inibidor de Quinase Dependente de Ciclina p21/urina , Rim/metabolismo , Traumatismo por Reperfusão/sangue , Traumatismo por Reperfusão/urina , Injúria Renal Aguda/genética , Injúria Renal Aguda/patologia , Fatores Etários , Envelhecimento/genética , Animais , Biomarcadores/sangue , Biomarcadores/urina , Encéfalo/metabolismo , Morte Celular , Inibidor de Quinase Dependente de Ciclina p21/genética , Modelos Animais de Doenças , Rim/patologia , Masculino , Camundongos , Miocárdio/metabolismo , Traumatismo por Reperfusão/genética , Fatores de Tempo , Regulação para CimaRESUMO
Background: P21, a cyclin kinase inhibitor, is upregulated by renal 'ischemic preconditioning' (IPC), and induces a 'cytoresistant' state. However, P21-induced cell cycle inhibition can also contribute to cellular senescence, a potential adverse renal event. Hence, this study assessed whether: (i) IPC-induced P21 upregulation is associated with subsequent renal senescence; and (ii) preconditioning can be established 'independent' of P21 induction and avoid a post-ischemic senescent state? Methods: CD-1 mice were subjected to either IPC (5-15 min) or to a recently proposed 'oxidant-induced preconditioning' (OIP) strategy (tin protoporphyrin-induced heme oxygenase inhibition +/- parental iron administration). P21 induction [messenger RNA (mRNA)/protein], cell proliferation (KI-67, phosphohistone H3 nuclear staining), kidney senescence (P16ink4a; P19Arf mRNAs; senescence-associated beta-galactosidase levels) and resistance to ischemic acute kidney injury were assessed. Results: IPC induced dramatic (10-25×) and persistent P21 activation and 'downstream' tubular senescence. Conversely, OIP did not upregulate P21, it increased, rather than decreased, cell proliferation markers, and it avoided a senescence state. OIP markedly suppressed ischemia-induced P21 up-regulation, it inhibited the development of post-ischemic senescence and it conferred near-complete protection against ischemic acute renal failure (ARF). To assess OIP's impact on a non-P21-dependent cytoprotective pathway, its ability to activate Nrf2, the so-called 'master regulator' of endogenous cell defenses, was assessed. Within 4 h, OIP activated each of three canonical Nrf2-regulated genes (NQO1, SRXN1, GCLC; 3- to 5-fold mRNA increases). Conversely, this gene activation pathway was absent in Nrf2-/- mice, confirming Nrf2 specificity. Nrf2-/- mice also did not develop significant OIP-mediated protection against ischemic ARF. Conclusions: OIP (i) activates the cytoprotective Nrf2, but not the P21, pathway; (ii) suppresses post-ischemic P21 induction and renal senescence; and (iii) confers marked protection against ischemic ARF. In sum, these findings suggest that OIP may be a clinically feasible approach for safely activating the Nrf2 pathway, and thereby confer protection against clinical renal injury.
Assuntos
Injúria Renal Aguda/prevenção & controle , Senescência Celular/efeitos dos fármacos , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Precondicionamento Isquêmico/métodos , Fator 2 Relacionado a NF-E2/fisiologia , Oxidantes/farmacologia , Animais , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Inibidor de Quinase Dependente de Ciclina p21/genética , Heme Oxigenase (Desciclizante)/antagonistas & inibidores , Masculino , Camundongos , Camundongos Knockout , Protoporfirinas/farmacologiaRESUMO
α1-Microglobulin (A1M) is a low-molecular-weight heme-binding antioxidant protein that is readily filtered by the glomerulus and reabsorbed by proximal tubules. Given these properties, recombinant A1M (rA1M) has been proposed as a renal antioxidant and therapeutic agent. However, little direct evidence to support this hypothesis exists. Hence, we have sought "proof of concept" in this regard. Cultured proximal tubule (HK-2) cells or isolated mouse proximal tubule segments were challenged with a variety of prooxidant insults: 1) hemin, 2) myoglobin; 3) "catalytic" iron, 4) H2O2/Fenton reagents, 5) a Ca(2+) ionophore, 6) antimycin A, or 7) hypoxia (with or without rA1M treatment). HK-2 injury was gauged by the percent lactate dehydrogenase release and 4,5-(dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide uptake. In vivo protection was sought in rA1M-treated mice subjected to 1) graded myohemoglobinura (2, 4, 8, or 9 ml/kg glycerol injection), 2) purified myoglobinemia/uria, or 3) endotoxemia. In vivo injury was assessed by blood urea nitrogen, creatinine, and the expression of redox-sensitive genes (heme oxygenase-1, neutrophil gelatinase-associated lipocalin, and monocyte chemoattractant protein-1 mRNAs). Although rA1M totally blocked in vitro hemin toxicity, equimolar albumin (another heme binder) or 10% serum induced equal protection. rA1M failed to mitigate any nonhemin forms of either in vitro or in vivo injury. A1M appeared to be rapidly degraded within proximal tubules (by Western blot analysis). Surprisingly, rA1M exerted select injury-promoting effects (increased in vitro catalytic iron/antimycin toxicities and increased in vivo monocyte chemoattractant protein-1/neutrophil gelatinase-associated lipocalin mRNA expression after glycerol or endotoxin injection). We conclude that rA1M has questionable utility as a renal antioxidant/cytoprotective agent, particularly in the presence of larger amounts of competitive free heme (e.g., albumin) binders.
Assuntos
Injúria Renal Aguda/prevenção & controle , alfa-Globulinas/farmacologia , Antioxidantes/farmacologia , Túbulos Renais Proximais/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Proteínas Recombinantes/farmacologia , Injúria Renal Aguda/metabolismo , Animais , Antimicina A/farmacologia , Linhagem Celular , Hemina/farmacologia , Humanos , Peróxido de Hidrogênio/farmacologia , Ferro/farmacologia , Túbulos Renais Proximais/metabolismo , Camundongos , Mioglobina/farmacologia , Substâncias Protetoras/farmacologiaRESUMO
Tissue preconditioning, whereby various short-term stressors initiate organ resistance to subsequent injury, is well recognized. However, clinical preconditioning of the kidney for protection against acute kidney injury (AKI) has not been established. Here we tested whether a pro-oxidant agent, iron sucrose, combined with a protoporphyrin (Sn protoporphyrin), can induce preconditioning and protect against acute renal failure. Mice were pretreated with iron sucrose, protoporphyrin, cyanocobalamin, iron sucrose and protoporphyrin, or iron sucrose and cyanocobalamin. Eighteen hours later, ischemic, maleate, or glycerol models of AKI were induced, and its severity was assessed the following day (blood urea nitrogen, plasma creatinine concentrations; post-ischemic histology). Agent impact on cytoprotective gene expression (heme oxygenase 1, hepcidin, haptoglobin, hemopexin, α1-antitrypsin, α1-microglobulin, IL-10) was assessed as renal mRNA and protein levels. AKI-associated myocardial injury was gauged by plasma troponin I levels. Combination agent administration upregulated multiple cytoprotective genes and, unlike single agent administration, conferred marked protection against each tested model of acute renal failure. Heme oxygenase was shown to be a marked contributor to this cytoprotective effect. Preconditioning also blunted AKI-induced cardiac troponin release. Thus, iron sucrose and protoporphyrin administration can upregulate diverse cytoprotective genes and protect against acute renal failure. Associated cardiac protection implies potential relevance to both AKI and its associated adverse downstream effects.
Assuntos
Injúria Renal Aguda/prevenção & controle , Compostos Férricos/uso terapêutico , Ácido Glucárico/uso terapêutico , Rim/metabolismo , Metaloporfirinas/uso terapêutico , Substâncias Protetoras/uso terapêutico , Protoporfirinas/uso terapêutico , Injúria Renal Aguda/sangue , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/patologia , alfa-Globulinas/metabolismo , Animais , Nitrogênio da Ureia Sanguínea , Creatinina/sangue , Modelos Animais de Doenças , Quimioterapia Combinada , Óxido de Ferro Sacarado , Glicerol/toxicidade , Haptoglobinas/metabolismo , Heme Oxigenase-1/metabolismo , Hemopexina/metabolismo , Hepcidinas/metabolismo , Interleucina-10/metabolismo , Rim/patologia , Masculino , Maleatos/toxicidade , Camundongos , RNA Mensageiro/metabolismo , Troponina C/sangue , alfa 1-Antitripsina/metabolismoRESUMO
Aberrant gene expression is a molecular hallmark of acute kidney injury (AKI). As epigenetic processes control gene expression in a cell- and environment-defined manner, understanding the epigenetic pathways that regulate genes altered by AKI may open vital new insights into the complexities of disease pathogenesis and identify possible therapeutic targets. Here we used matrix chromatin immunoprecipitation and integrative analysis to study 20 key permissive and repressive epigenetic histone marks at transcriptionally induced Tnf, Ngal, Kim-1, and Icam-1 genes in mouse models of AKI; unilateral renal ischemia/reperfusion, lipopolysaccharide (LPS), and their synergistically injurious combination. Results revealed unexpected heterogeneity of transcriptional and epigenetic responses. Tnf and Ngal were transcriptionally upregulated in response to both treatments individually, and to combination treatment. Kim-1 was induced by ischemia/reperfusion and Icam-1 by LPS only. Epigenetic alterations at these genes exhibited distinct time-dependent changes that shared some similarities, such as reduction in repressive histone modifications, and also had major ischemia/reperfusion versus endotoxin differences. Thus, diversity of changes at AKI genes in response to different insults indicates involvement of several epigenetic pathways. This could be exploited pharmacologically through rational-drug design to alter the course and improve clinical outcomes of this syndrome.
Assuntos
Injúria Renal Aguda/genética , Epigênese Genética , Rim , Lipopolissacarídeos , Traumatismo por Reperfusão/genética , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/metabolismo , Proteínas de Fase Aguda/genética , Proteínas de Fase Aguda/metabolismo , Animais , Imunoprecipitação da Cromatina , Modelos Animais de Doenças , Perfilação da Expressão Gênica/métodos , Regulação da Expressão Gênica , Receptor Celular 1 do Vírus da Hepatite A , Sequenciamento de Nucleotídeos em Larga Escala , Histonas/metabolismo , Molécula 1 de Adesão Intercelular/genética , Molécula 1 de Adesão Intercelular/metabolismo , Rim/metabolismo , Lipocalina-2 , Lipocalinas/genética , Lipocalinas/metabolismo , Masculino , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Proteínas Oncogênicas/genética , Proteínas Oncogênicas/metabolismo , RNA Polimerase II/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Traumatismo por Reperfusão/complicações , Traumatismo por Reperfusão/metabolismo , Fatores de Tempo , Transcrição Gênica , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Pyruvate is a key intermediary in energy metabolism and can exert antioxidant and anti-inflammatory effects. However, the fate of pyruvate during AKI remains unknown. Here, we assessed renal cortical pyruvate and its major determinants (glycolysis, gluconeogenesis, pyruvate dehydrogenase [PDH], and H2O2 levels) in mice subjected to unilateral ischemia (15-60 minutes; 0-18 hours of vascular reflow) or glycerol-induced ARF. The fate of postischemic lactate, which can be converted back to pyruvate by lactate dehydrogenase, was also addressed. Ischemia and glycerol each induced persistent pyruvate depletion. During ischemia, decreasing pyruvate levels correlated with increasing lactate levels. During early reperfusion, pyruvate levels remained depressed, but lactate levels fell below control levels, likely as a result of rapid renal lactate efflux. During late reperfusion and glycerol-induced AKI, pyruvate depletion corresponded with increased gluconeogenesis (pyruvate consumption). This finding was underscored by observations that pyruvate injection increased renal cortical glucose content in AKI but not normal kidneys. AKI decreased PDH levels, potentially limiting pyruvate to acetyl CoA conversion. Notably, pyruvate therapy mitigated the severity of AKI. This renoprotection corresponded with increases in cytoprotective heme oxygenase 1 and IL-10 mRNAs, selective reductions in proinflammatory mRNAs (e.g., MCP-1 and TNF-α), and improved tissue ATP levels. Paradoxically, pyruvate increased cortical H2O2 levels. We conclude that AKI induces a profound and persistent depletion of renal cortical pyruvate, which may induce additional injury.
Assuntos
Injúria Renal Aguda/metabolismo , Córtex Renal/metabolismo , Ácido Pirúvico/metabolismo , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/fisiopatologia , Trifosfato de Adenosina/metabolismo , Animais , Gluconeogênese/fisiologia , Glucose/metabolismo , Glicogênio/metabolismo , Peróxido de Hidrogênio/metabolismo , Isquemia/metabolismo , Isquemia/fisiopatologia , Córtex Renal/fisiopatologia , Túbulos Renais/metabolismo , Ácido Láctico/metabolismo , Masculino , Camundongos , Complexo Piruvato Desidrogenase/metabolismo , Traumatismo por Reperfusão/metabolismo , Traumatismo por Reperfusão/fisiopatologiaRESUMO
Hepatic ischemic-reperfusion injury (HIRI) is considered a risk factor for clinical acute kidney injury (AKI). However, HIRI's impact on renal tubular cell homeostasis and subsequent injury responses remain ill-defined. To explore this issue, 30-45 min of partial HIRI was induced in CD-1 mice. Sham-operated or normal mice served as controls. Renal changes and superimposed injury responses (glycerol-induced AKI; endotoxemia) were assessed 2-18 h later. HIRI induced mild azotemia (blood urea nitrogen â¼45 mg/dl) in the absence of renal histologic injury or proteinuria, implying a "prerenal" state. However, marked renal cortical, and isolated proximal tubule, cytoprotective "stress protein" gene induction (neutrophil gelatinase-associated lipocalin, heme oxygenase-1, hemopexin, hepcidin), and increased Toll-like receptor 4 (TLR4) expression resulted (protein/mRNA levels). Ischemia caused release of hepatic heme-based proteins (e.g., cytochrome c) into the circulation. This corresponded with renal cortical oxidant stress (malondialdehyde increases). That hepatic derived factors can evoke redox-sensitive "stress protein" induction was implied by the following: peritoneal dialysate from HIRI mice, soluble hepatic extract, or exogenous cytochrome c each induced the above stress protein(s) either in vivo or in cultured tubule cells. Functional significance of HIRI-induced renal "preconditioning" was indicated by the following: 1) HIRI conferred virtually complete morphologic protection against glycerol-induced AKI (in the absence of hyperbilirubinemia) and 2) HIRI-induced TLR4 upregulation led to a renal endotoxin hyperresponsive state (excess TNF-α/MCP-1 gene induction). In conclusion, HIRI can evoke "renal preconditioning," likely due, in part, to hepatic release of pro-oxidant factors (e.g., cytochrome c) into the systemic circulation. The resulting renal changes can impact subsequent AKI susceptibility and TLR4 pathway-mediated stress.
Assuntos
Córtex Renal/fisiopatologia , Falência Hepática Aguda/fisiopatologia , Traumatismo por Reperfusão/fisiopatologia , Estresse Fisiológico , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/patologia , Proteínas de Fase Aguda/metabolismo , Animais , Linhagem Celular , Quimiocina CCL2/metabolismo , Endotoxemia/metabolismo , Heme Oxigenase-1/metabolismo , Hemopexina/metabolismo , Hepcidinas/metabolismo , Rim/metabolismo , Rim/patologia , Córtex Renal/metabolismo , Córtex Renal/patologia , Lipocalina-2 , Lipocalinas/metabolismo , Lipopolissacarídeos , Falência Hepática Aguda/complicações , Falência Hepática Aguda/patologia , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Proteínas Oncogênicas/metabolismo , Traumatismo por Reperfusão/complicações , Traumatismo por Reperfusão/patologia , Receptor 4 Toll-Like/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
There is an increasing number of clinical studies suggesting that acute kidney injury (AKI) can be complicated by the onset of progressive renal disease. Indeed, given the frequency of AKI in hospitalized patients, it could potentially be a leading cause of, or contributor to, end-stage renal disease. Insights into the natural history of AKI and potential mechanisms for disease progression can be gleaned from experimental studies. Although such studies underscore the principle that AKI can 'heal with defects', whether ongoing renal disease develops remains a subject of debate. Indeed, in the aftermath of AKI, a variety of secondary renal protective pathways are activated, which may retard or prevent severe chronic kidney disease. Furthermore, the onset of acute uremia per se may exert surprisingly potent renal protective effects. The purpose of this brief report is to review some of the clinical and experimental data that deal with these complex issues.
Assuntos
Injúria Renal Aguda/complicações , Insuficiência Renal Crônica/etiologia , Injúria Renal Aguda/fisiopatologia , Injúria Renal Aguda/terapia , Animais , Anti-Inflamatórios/uso terapêutico , Nitrogênio da Ureia Sanguínea , Modelos Animais de Doenças , Progressão da Doença , Endotelina-1/biossíntese , Endotelina-1/genética , Glucocorticoides/uso terapêutico , Humanos , Rim/irrigação sanguínea , Nefrite Intersticial/etiologia , Nefrite Intersticial/patologia , Insuficiência Renal Crônica/fisiopatologia , Insuficiência Renal Crônica/prevenção & controle , Terapia de Substituição Renal , Traumatismo por Reperfusão/etiologia , Traumatismo por Reperfusão/patologia , Traumatismo por Reperfusão/fisiopatologia , Uremia/etiologia , Uremia/patologiaRESUMO
Pyruvate is a key intermediary in both aerobic and anaerobic energy metabolisms. In addition, a burgeoning body of experimental literature indicates that it can also dramatically impact oxidant, proinflammatory, and cytoprotective pathways. In sum, these actions can confer protection against diverse forms of tissue damage. However, the fate of pyruvate during the evolution of acute kidney injury (AKI) has remained ill defined. Recent experimental studies have indicated that following either ischemic or nephrotoxic renal injury, marked and sustained pyruvate depletion results. While multiple potential mechanisms for this pyruvate loss may be involved, experimental data suggest that a loss of lactate (a dominant pyruvate precursor) and enhanced gluconeogenesis (i.e. pyruvate utilization) are involved. The importance of pyruvate depletion for AKI pathogenesis is underscored by observations that pyruvate therapy can attenuate diverse forms of experimental AKI. This protection may stem from reductions in tissue inflammation, improved anti-inflammatory defenses, and an enhanced cellular energy metabolism. The pieces of information that give rise to these conclusions are discussed in this brief report.
Assuntos
Injúria Renal Aguda/etiologia , Córtex Renal/metabolismo , Piruvatos/metabolismo , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Antioxidantes/farmacologia , Antioxidantes/uso terapêutico , Hipóxia Celular , Descarboxilação , Modelos Animais de Doenças , Metabolismo Energético , Gluconeogênese , Glicólise , Humanos , Peróxido de Hidrogênio/metabolismo , Inflamação , Isquemia/metabolismo , Isquemia/fisiopatologia , Rim/irrigação sanguínea , Lactatos/metabolismo , Oxirredução , Estresse Oxidativo , Rabdomiólise/complicaçõesRESUMO
Background: RBT-1 is a combination drug of stannic protoporfin (SnPP) and iron sucrose (FeS) that elicits a preconditioning response through activation of antioxidant, anti-inflammatory, and iron-scavenging pathways, as measured by heme oxygenase-1 (HO-1), interleukin-10 (IL-10), and ferritin, respectively. Our primary aim was to determine whether RBT-1 administered before surgery would safely and effectively elicit a preconditioning response in patients undergoing cardiac surgery. Methods: This phase 2, double-blind, randomised, placebo-controlled, parallel-group, adaptive trial, conducted in 19 centres across the USA, Canada, and Australia, enrolled patients scheduled to undergo non-emergent coronary artery bypass graft (CABG) and/or heart valve surgery with cardiopulmonary bypass. Patients were randomised (1:1:1) to receive either a single intravenous infusion of high-dose RBT-1 (90 mg SnPP/240 mg FeS), low-dose RBT-1 (45 mg SnPP/240 mg FeS), or placebo within 24-48 h before surgery. The primary outcome was a preoperative preconditioning response, measured by a composite of plasma HO-1, IL-10, and ferritin. Safety was assessed by adverse events and laboratory parameters. Prespecified adaptive criteria permitted early stopping and enrichment. This trial is registered with ClinicalTrials.gov, NCT04564833. Findings: Between Aug 4, 2021, and Nov 9, 2022, of 135 patients who were enrolled and randomly allocated to a study group (46 high-dose, 45 low-dose, 44 placebo), 132 (98%) were included in the primary analysis (46 high-dose, 42 low-dose, 44 placebo). At interim, the trial proceeded to full enrollment without enrichment. RBT-1 led to a greater preconditioning response than did placebo at high-dose (geometric least squares mean [GLSM] ratio, 3.58; 95% CI, 2.91-4.41; p < 0.0001) and low-dose (GLSM ratio, 2.62; 95% CI, 2.11-3.24; p < 0.0001). RBT-1 was generally well tolerated by patients. The primary drug-related adverse event was dose-dependent photosensitivity, observed in 12 (26%) of 46 patients treated with high-dose RBT-1 and in six (13%) of 45 patients treated with low-dose RBT-1 (safety population). Interpretation: RBT-1 demonstrated a statistically significant cytoprotective preconditioning response and a manageable safety profile. Further research is needed. A phase 3 trial is planned. Funding: Renibus Therapeutics, Inc.
RESUMO
Oxidative stress and inflammation are mediators in the development and progression of chronic kidney disease (CKD) and its complications, and they are inseparably linked as each begets and amplifies the other. CKD-associated oxidative stress is due to increased production of reactive oxygen species (ROS) and diminished antioxidant capacity. The latter is largely caused by impaired activation of Nrf2, the transcription factor that regulates genes encoding antioxidant and detoxifying molecules. Protective effects of Nrf2 are evidenced by amelioration of oxidative stress, inflammation, and kidney disease in response to natural Nrf2 activators in animal models, while Nrf2 deletion amplifies these pathogenic pathways and leads to autoimmune nephritis. Given the role of impaired Nrf2 activity in CKD-induced oxidative stress and inflammation, interventions aimed at restoring Nrf2 may be effective in retarding CKD progression. Clinical trials of the potent Nrf2 activator bardoxolone methyl showed significant improvement in renal function in CKD patients with type 2 diabetes. However, due to unforeseen complications the BEACON trial, which was designed to investigate the effect of this drug on time to end-stage renal disease or cardiovascular death in patients with advanced CKD, was prematurely terminated. This article provides an overview of the role of impaired Nrf2 activity in the pathogenesis of CKD-associated oxidative stress and inflammation and the potential utility of targeting Nrf2 in the treatment of CKD.
Assuntos
Anti-Infecciosos/uso terapêutico , Antioxidantes/uso terapêutico , Inflamação/tratamento farmacológico , Rim/efeitos dos fármacos , Fator 2 Relacionado a NF-E2/agonistas , Ácido Oleanólico/análogos & derivados , Estresse Oxidativo/efeitos dos fármacos , Insuficiência Renal Crônica/tratamento farmacológico , Injúria Renal Aguda/tratamento farmacológico , Injúria Renal Aguda/imunologia , Injúria Renal Aguda/metabolismo , Animais , Progressão da Doença , Humanos , Inflamação/diagnóstico , Inflamação/imunologia , Inflamação/metabolismo , Rim/imunologia , Rim/metabolismo , Falência Renal Crônica/tratamento farmacológico , Falência Renal Crônica/imunologia , Falência Renal Crônica/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Ácido Oleanólico/uso terapêutico , Insuficiência Renal Crônica/diagnóstico , Insuficiência Renal Crônica/imunologia , Insuficiência Renal Crônica/metabolismo , Fatores de Tempo , Resultado do TratamentoRESUMO
This study assessed whether endothelin-1 (ET-1) helps mediate postischemic acute kidney injury (AKI) progression to chronic kidney disease (CKD). The impact(s) of potent ETA or ETB receptor-specific antagonists (Atrasentan and BQ-788, respectively) on disease progression were assessed 24 h or 2 weeks following 30 min of unilateral ischemia in CD-1 mice. Unilateral ischemia caused progressive renal ET-1 protein/mRNA increases with concomitant ETA, but not ETB, mRNA elevations. Extensive histone remodeling consistent with gene activation and increased RNA polymerase II (Pol II) binding occurred at the ET-1 gene. Unilateral ischemia produced progressive renal injury as indicated by severe histologic injury and a 40% loss of renal mass. Pre- and post-ischemia or just postischemic treatment with Atrasentan conferred dramatic protective effects such as decreased tubule/microvascular injury, normalized tissue lactate, and total preservation of renal mass. Nuclear KI-67 staining was not increased by Atrasentan, implying that increased tubule proliferation was not involved. Conversely, ETB blockade had no protective effect. Thus, our findings provide the first evidence that ET-1 operating through ETA can have a critical role in ischemic AKI progression to CKD. Blockade of ETA provided dramatic protection, indicating the functional significance of these results.
Assuntos
Progressão da Doença , Endotelina-1/genética , Endotelina-1/fisiologia , Falência Renal Crônica/fisiopatologia , Insuficiência Renal Crônica/fisiopatologia , Traumatismo por Reperfusão/fisiopatologia , Animais , Atrasentana , Modelos Animais de Doenças , Antagonistas do Receptor de Endotelina A , Antagonistas do Receptor de Endotelina B , Falência Renal Crônica/etiologia , Masculino , Camundongos , Camundongos Endogâmicos , Oligopeptídeos/farmacologia , Piperidinas/farmacologia , Pirrolidinas/farmacologia , RNA Mensageiro/genética , Receptor de Endotelina A/efeitos dos fármacos , Receptor de Endotelina A/fisiologia , Receptor de Endotelina B/efeitos dos fármacos , Receptor de Endotelina B/fisiologia , Insuficiência Renal Crônica/etiologia , Traumatismo por Reperfusão/complicaçõesRESUMO
Following the induction of ischemic or toxin-mediated acute kidney injury (AKI), cellular adaptations occur that 're-program' how the kidney responds to future superimposed insults. This re-programming is not simply a short-lived phenomenon; rather it can persist for many weeks, implying that a state of 'biologic memory' has emerged. These changes can be both adaptive and maladaptive in nature and they can co-exist in time. A beneficial adaptation is the emergence of acquired cytoresistance, whereby a number of physiologic responses develop that serve to protect the kidney against further ischemic or nephrotoxic attack. Conversely, some changes are maladaptive, such as a predisposition to Gram-negative or Gram-positive bacteremia due to a renal tubular up-regulation of toll-like receptor responses. This latter change culminates in exaggerated cytokine production, and with efflux into the systemic circulation, extra-renal tissue injury can result (so-called 'organ cross talk'). Another maladaptive response is a persistent up-regulation of pro-inflammatory, pro-fibrotic and vasoconstrictive genes, culminating in progressive renal injury and ultimately end-stage renal failure. The mechanisms by which this biologic re-programming, or biologic memory, is imparted remain subjects for considerable debate. However, injury-induced, and stable, epigenetic remodeling at pro-inflammatory/pro-fibrotic genes seems likely to be involved. The goal of this editorial is to highlight that the so-called 'maintenance phase' of acute renal failure is not a static one, somewhere between injury induction and the onset of repair. Rather, this period is one in which the induction of 'biologic memory' can ultimately impact renal functional recovery, extra-renal injury and the possible transition of AKI into chronic, progressive renal disease.
Assuntos
Injúria Renal Aguda/imunologia , Tolerância a Medicamentos , Hipersensibilidade , Memória Imunológica/imunologia , Falência Renal Crônica/etiologia , Receptores Toll-Like/metabolismo , Injúria Renal Aguda/complicações , Animais , Citoproteção , Progressão da Doença , Humanos , Falência Renal Crônica/metabolismo , Falência Renal Crônica/patologiaRESUMO
BACKGROUND: Recent experimental work suggests a paradox: although uremia evokes systemic toxicities, in the setting of AKI, it can induce intrarenal cytoprotective and anti-inflammatory effects. Whether these influences can attenuate post-ischemic kidney disease progression remains unknown. METHODS: To explore this possibility, male CD-1 mice were subjected to a 30-min unilateral (left) kidney ischemia model, previously shown to reduce renal mass by â¼50% over 2-3 weeks. Stepwise azotemia/acute uremia was superimposed by inducing different lengths of contralateral (right) kidney ischemia (0, 15, 18, 20 min). Subsequent loss of left renal mass (kidney weight) was assessed 2 weeks later and contrasted with the degree of initial azotemia 24-h BUN. RESULTS: A striking correlation between 24-h BUNs and 2-week left renal mass was observed (r, 0.77; P < 0.001). With 20 min of right kidney ischemia, left kidney size was completely preserved. This preservation did not result from increased tubular cell proliferation or decreased microvascular loss, as gauged by KI-67 and CD-34 immunohistochemistry, respectively. Rather, an early reduction in proximal tubule cell dropout (as judged by renal cortical N-acetyl-glucosaminidase content), with a subsequent preservation of tubule mass, was observed. CONCLUSIONS: In summary, these findings advance a novel concept: acute uremia can confer early post-ischemic cytoprotection resulting in a slowed progression of post-ischemic kidney disease.