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The involvement of cell death in acute kidney injury (AKI) is linked to multiple factors including energy depletion, electrolyte imbalance, reactive oxygen species, inflammation, mitochondrial dysfunction, and activation of several cell death pathway components. Since our review in 2003, discussing the relative contributions of apoptosis and necrosis, several other forms of cell death have been identified and are shown to contribute to AKI. Currently, these various forms of cell death can be fundamentally divided into accidental cell death and regulated or programmed cell death based on functional aspects. Several death initiator and effector molecules switch molecules that may act as signaling components triggering either death or protective mechanisms or alternate cell death pathways have been identified as part of the machinery. Intriguingly, several of these cell death pathways share components and signaling pathways suggesting complementary or compensatory functions. Thus, defining the cross talk between distinct cell death pathways and identifying the unique molecular effectors for each type of cell death may be required to develop novel strategies to prevent cell death. Furthermore, depending on the multiple forms of cell death simultaneously induced in different AKI settings, strategies for combination therapies that block multiple cell death pathways need to be developed to completely prevent injury, cell death, and renal function. This review highlights the various cell death pathways, cross talk, and interactions between different cell death modalities in AKI.
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Lesión Renal Aguda , Apoptosis , Transducción de Señal , Lesión Renal Aguda/patología , Lesión Renal Aguda/metabolismo , Lesión Renal Aguda/fisiopatología , Humanos , Animales , Riñón/patología , Riñón/metabolismo , Necroptosis , Necrosis , Muerte CelularRESUMEN
Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites with biological effects, including antiapoptotic, anti-inflammatory, and antifibrotic functions. Soluble epoxide hydrolase (sEH)-mediated hydrolysis of EETs to dihydroxyeicosatrienoic acids (DHETs) attenuates these effects. Recent studies have demonstrated that inhibition of sEH prevents renal tubulointerstitial fibrosis and inflammation in the chronic kidney disease model. Given the pathophysiological role of the EET pathway in chronic kidney disease, we investigated if administration of EET regioisomers and/or sEH inhibition will promote antifibrotic and renoprotective effects in renal fibrosis following unilateral ureteral obstruction (UUO). EETs administration abolished tubulointerstitial fibrogenesis, as demonstrated by reduced fibroblast activation and collagen deposition after UUO. The inflammatory response was prevented as demonstrated by decreased neutrophil and macrophage infiltration and expression of cytokines in EET-administered UUO kidneys. EET administration and/or sEH inhibition significantly reduced M1 macrophage markers, whereas M2 macrophage markers were highly upregulated. Furthermore, UUO-induced oxidative stress, tubular injury, and apoptosis were all downregulated following EET administration. Combined EET administration and sEH inhibition, however, had no additive effect in attenuating inflammation and renal interstitial fibrogenesis after UUO. Taken together, our findings provide a mechanistic understanding of how EETs prevent kidney fibrogenesis during obstructive nephropathy and suggest EET treatment as a potential therapeutic strategy to treat fibrotic diseases.NEW & NOTEWORTHY Epoxyeicosatrienoic acids (EETs) are cytochrome P-450-dependent antihypertensive and anti-inflammatory derivatives of arachidonic acid, which are highly abundant in the kidney and considered renoprotective. We found that EET administration and/or soluble epoxide hydrolase inhibition significantly attenuates oxidative stress, renal cell death, inflammation, macrophage differentiation, and fibrogenesis following unilateral ureteral obstruction. Our findings provide a mechanistic understanding of how EETs prevent kidney fibrogenesis during obstructive nephropathy and suggest that EET treatment may be a potential therapeutic strategy to treat fibrotic diseases.
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Insuficiencia Renal Crónica , Obstrucción Ureteral , Humanos , Epóxido Hidrolasas , Obstrucción Ureteral/complicaciones , Obstrucción Ureteral/tratamiento farmacológico , Riñón/metabolismo , Eicosanoides/metabolismo , Inflamación , Ácidos Araquidónicos , Ácido 8,11,14-EicosatrienoicoRESUMEN
Kidney ischemia/reperfusion (I/R) injury, a common cause of acute kidney injury (AKI), is associated with the migration of inflammatory cells into the kidney. Ras-related C3 botulinum toxin substrate 1 (Rac1), a member of the Rho family of small GTPase, plays an important role in inflammatory cell migration by cytoskeleton rearrangement. Here, we investigated the role of Rac1 on kidney I/R injury and macrophage migration. Male mice were subjected to either 25 min of bilateral ischemia followed by reperfusion (I/R) or a sham operation. Some mice were administrated with either NSC23766, an inhibitor of Rac1, or 0.9% NaCl (vehicle). Kidney damage and Rac1 activity and expression were measured. The migration and lamellipodia formation of RAW264.7 cells, mouse monocyte/macrophage, induced by monocyte chemoattractant protein-1 (MCP-1, a chemokine) were determined using transwell migration assay and phalloidin staining, respectively. In sham-operated kidneys, Rac1 was expressed in tubular cells and interstitial cells. In I/R-injured kidneys, Rac1 expression was decreased in tubule cells in correlation with the damage of tubular cells, whereas Rac1 expression increased in the interstitium in correlation with an increased population of F4/80 cells, monocytes/macrophages. I/R increased Rac1 activity without changing total Rac1 expression in the whole kidney lysates. NSC23766 administration blocked Rac1 activation and protected the kidney against I/R-induced kidney damage and interstitial F4/80 cell increase. NSC23766 suppressed monocyte MCP-1-induced lamellipodia and filopodia formation and migration of RAW 264.7 cells. These results indicate Rac1 inhibition protects the kidney against I/R via inhibition of monocytes/macrophages migration into the kidney.
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Components of the renin-angiotensin system, including angiotensinogen (AGT), are critical contributors to chronic kidney disease (CKD) development and progression. However, the specific role of tissue-derived AGTs in CKD has not been fully understood. To define the contribution of liver versus kidney AGT in the CKD development, we performed 5/6 nephrectomy (Nx), an established CKD model, in wild-type (WT), proximal tubule (PT)- or liver-specific AGT knockout (KO) mice. Nx significantly elevated intrarenal AGT expression and elevated blood pressure (BP) in WT mice. The increase of intrarenal AGT protein was completely blocked in liver-specific AGT KO mice with BP reduction, suggesting a crucial role for liver AGT in BP regulation during CKD. Nx-induced glomerular and kidney injury and dysfunction, as well as fibrosis, were all attenuated to a greater extent in liver-specific AGT KO mice compared with PT-specific AGT KO and WT mice. However, the suppression of interstitial fibrosis in PT- and liver-specific AGT KO mouse kidneys was comparable. Our findings demonstrate that liver AGT acts as a critical contributor in driving glomerular and tubular injury, renal dysfunction, and fibrosis progression, whereas the role of PT AGT was limited to interstitial fibrosis progression in chronic renal insufficiency. Our results provide new insights for the development of tissue-targeted renin-angiotensin system intervention in the treatment of CKD.NEW & NOTEWORTHY Chronic kidney disease (CKD) is a major unmet medical need with no effective treatment. Current findings demonstrate that hepatic and proximal tubule angiotensinogen have distinct roles in tubular and glomerular injury, fibrogenesis, and renal dysfunction during CKD development. As renin-angiotensin system components, including angiotensinogen, are important targets for treating CKD in the clinic, the results from our study may be applied to developing better tissue-targeted treatment strategies for CKD and other fibroproliferative diseases.
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Insuficiencia Renal Crónica , Insuficiencia Renal , Angiotensinógeno/genética , Angiotensinógeno/metabolismo , Animales , Fibrosis , Riñón/metabolismo , Hígado/metabolismo , Ratones , Insuficiencia Renal/metabolismo , Insuficiencia Renal Crónica/metabolismo , Sistema Renina-AngiotensinaRESUMEN
The proximal tubule (PT) is highly vulnerable to acute injury, including ischemic insult and nephrotoxins, and chronic kidney injury. It has been established that PT injury is a primary cause of the development of chronic kidney disease, but the underlying molecular mechanism remains to be defined. Here, we tested whether PT cyclophilin D (CypD), a mitochondrial matrix protein, is a critical factor to cause kidney fibrosis progression. To define the role of CypD in kidney fibrosis, we used an established mouse model for kidney fibrosis: the unilateral ureteral obstruction (UUO) model in global and PT-specific CypD knockout (KO). Global CypD KO blunted kidney fibrosis progression with inhibition of myofibroblast activation and fibrosis. UUO-induced tubular atrophy was suppressed in kidneys of global CypD KO but not tubular dilation or apoptotic cell death. PT cell cycle arrest was highly increased in wild-type UUO kidneys but was markedly attenuated in global CypD KO UUO kidneys. The number of macrophages and neutrophils was less in UUO kidneys of global CypD KO than those of wild-type kidneys. Proinflammatory and profibrotic factors were all inhibited in global CypD KO. In line with those of global CypD KO, PT-specific CypD KO also blunted kidney fibrosis progression, along with less tubular atrophy, renal parenchymal loss, cell cycle arrest in PT, and inflammation, indicating a critical role for PT CypD in fibrogenesis. Collectively, our data demonstrate that CypD in the PT is a critical factor contributing to kidney fibrosis in UUO, providing a new paradigm for mitochondria-targeted therapeutics of fibrotic diseases.NEW & NOTEWORTHY It has been established that renal proximal tubule (PT) injury is a primary cause of the development of chronic kidney disease, but the underlying molecular mechanism remains to be defined. Here, we show that cyclophilin D, a mitochondrial matrix protein, in the PT causes kidney fibrogenesis in obstructive nephropathy. Our data suggest that targeting PT cyclophilin D could be beneficial to prevent fibrosis progression.
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Fibrosis/metabolismo , Enfermedades Renales/metabolismo , Enfermedades Renales/patología , Túbulos Renales Proximales/metabolismo , Peptidil-Prolil Isomerasa F/metabolismo , Animales , Apoptosis , Puntos de Control del Ciclo Celular , Regulación de la Expresión Génica , Enfermedades Renales/etiología , Ligadura , Masculino , Ratones , Ratones NoqueadosRESUMEN
Mitochondrial NADP+-dependent isocitrate dehydrogenase 2 (IDH2) produces NADPH, which is known to inhibit mitochondrial oxidative stress. Ureteral obstruction induces kidney inflammation and fibrosis via oxidative stress. Here, we investigated the role and underlying mechanism of IDH2 in unilateral ureteral obstruction (UUO)-induced kidney inflammation using IDH2 gene deleted mice (IDH2-/-). Eight- to 10-week-old female IDH2-/- mice and wild type (IDH2+/+) littermates were subjected to UUO and kidneys were harvested 5 days after UUO. IDH2 was not detected in the kidneys of IDH2-/- mice, while UUO decreased IDH2 in IDH2+/+ mice. UUO increased the expressions of markers of oxidative stress in both IDH2+/+ and IDH2-/- mice, and these changes were greater in IDH2-/- mice compared to IDH2+/+ mice. Bone marrow-derived macrophages of IDH2-/- mice showed a more migrating phenotype with greater ruffle formation and Rac1 distribution than that of IDH2+/+ mice. Correspondently, UUO-induced infiltration of monocytes/macrophages was greater in IDH2-/- mice compared to IDH2+/+ mice. Taken together, these data demonstrate that IDH2 plays a protective role against UUO-induced inflammation through inhibition of oxidative stress and macrophage infiltration.
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Regardless of the etiology, acute kidney injury involves aspects of mitochondrial dysfunction and ATP depletion. Fatty acid oxidation is the preferred energy source of the kidney and is inhibited during acute kidney injury. A pivotal role for the mitochondrial matrix protein, cyclophilin D in regulating overall cell metabolism is being unraveled. We hypothesize that mitochondrial interaction of proximal tubule cyclophilin D and the transcription factor PPARα modulate fatty acid beta-oxidation in cisplatin-induced acute kidney injury. Cisplatin injury resulted in histological and functional damage in the kidney with downregulation of fatty acid oxidation genes and increase of intrarenal lipid accumulation. However, proximal tubule-specific deletion of cyclophilin D protected the kidneys from the aforementioned effects. Mitochondrial translocation of PPARα, its binding to cyclophilin D, and sequestration led to inhibition of its nuclear translocation and transcription of PPARα-regulated fatty acid oxidation genes during cisplatin-induced acute kidney injury. Genetic or pharmacological inhibition of cyclophilin D preserved nuclear expression and transcriptional activity of PPARα and prevented the impairment of fatty acid oxidation and intracellular lipid accumulation. Docking analysis identified potential binding sites between PPARα and cyclophilin D. Thus, our results indicate that proximal tubule cyclophilin D elicits impaired mitochondrial fatty acid oxidation via mitochondrial interaction between cyclophilin D and PPARα. Hence, targeting their interaction may be a potential therapeutic strategy to prevent energy depletion, lipotoxicity and cell death in cisplatin-induced acute kidney injury.
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Lesión Renal Aguda , Cisplatino , Lesión Renal Aguda/inducido químicamente , Cisplatino/toxicidad , Peptidil-Prolil Isomerasa F , Ácidos Grasos , Humanos , Túbulos Renales ProximalesRESUMEN
The kidney is innervated by afferent sensory and efferent sympathetic nerve fibers. Norepinephrine (NE) is the primary neurotransmitter for post-ganglionic sympathetic adrenergic nerves, and its signaling, regulated through adrenergic receptors (AR), modulates renal function and pathophysiology under disease conditions. Renal sympathetic overactivity and increased NE level are commonly seen in chronic kidney disease (CKD) and are critical factors in the progression of renal disease. Blockade of sympathetic nerve-derived signaling by renal denervation or AR blockade in clinical and experimental studies demonstrates that renal nerves and its downstream signaling contribute to progression of acute kidney injury (AKI) to CKD and fibrogenesis. This review summarizes our current knowledge of the role of renal sympathetic nerve and adrenergic receptors in AKI, AKI to CKD transition and CKDand provides new insights into the therapeutic potential of intervening in its signaling pathways.
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Lesión Renal Aguda/metabolismo , Riñón/inervación , Insuficiencia Renal Crónica/metabolismo , Transducción de Señal , Sistema Nervioso Simpático/metabolismo , Animales , Humanos , Receptores Adrenérgicos/metabolismoRESUMEN
Migration of surviving kidney tubule cells after sub-lethal injury, for example ischemia/reperfusion (I/R), plays a critical role in recovery. Exocytosis is known to be involved in cell migration, and a key component in exocytosis is the highly-conserved eight-protein exocyst complex. We investigated the expression of a central exocyst complex member, Sec10, in kidneys following I/R injury, as well as the role of Sec10 in wound healing following scratch injury of cultured Madin-Darby canine kidney (MDCK) cells. Sec10 overexpression and knockdown (KD) in MDCK cells were used to investigate the speed of wound healing and the mechanisms underlying recovery. In mice, Sec10 decreased after I/R injury, and increased during the recovery period. In cell culture, Sec10 OE inhibited ruffle formation and wound healing, while Sec10 KD accelerated it. Sec10 OE cells had higher amounts of diacylglycerol kinase (DGK) gamma at the leading edge than did control cells. A DGK inhibitor reversed the inhibition of wound healing and ruffle formation in Sec10 OE cells. Conclusively, downregulation of Sec10 following I/R injury appears to accelerate recovery of kidney tubule cells through activated ruffle formation and enhanced cell migration.
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Diacilglicerol Quinasa/antagonistas & inhibidores , Túbulos Renales/metabolismo , Daño por Reperfusión/prevención & control , Proteínas de Transporte Vesicular/genética , Animales , Bioensayo , Línea Celular , Movimiento Celular/efectos de los fármacos , Diacilglicerol Quinasa/genética , Diacilglicerol Quinasa/metabolismo , Perros , Inhibidores Enzimáticos/farmacología , Exocitosis , Regulación de la Expresión Génica , Túbulos Renales/patología , Células de Riñón Canino Madin Darby , Masculino , Ratones , Ratones Endogámicos C57BL , Piperidinas/farmacología , Quinazolinonas/farmacología , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Daño por Reperfusión/genética , Daño por Reperfusión/metabolismo , Daño por Reperfusión/patología , Proteínas de Transporte Vesicular/agonistas , Proteínas de Transporte Vesicular/antagonistas & inhibidores , Proteínas de Transporte Vesicular/metabolismo , Cicatrización de Heridas/fisiologíaRESUMEN
Fibrosis is an undesirable consequence of injury and a critical problem in many diseases. Recent studies have demonstrated an association of C/EBP homologous protein (CHOP) with fibrosis. We investigated the mechanism of CHOP in kidney fibrosis progression after unilateral ureteral obstruction (UUO) using Chop gene-deleted (Chop-/-) mice and their wild-type littermates (Chop+/+). UUO-induced kidney fibrosis was reduced in the Chop-/- than Chop+/+ mice. After UUO, CHOP expression was detected in the cytosol and nucleus of distal tubule cells and collecting duct cells of the kidney. UUO formed the autophagosome and increased the expression of autophagy proteins, Beclin-1, LC3-I and II, and p62 in the kidneys. These UUO-induced changes were significantly reduced in Chop-/- mice. Furthermore, Chop gene deletion attenuated mitochondrial fragmentation with lower expression of Fis-1, a mitochondrial fission protein, but higher expression of Opa-1, a mitochondrial fusion protein, than that seen in the wild-type mice. UUO disrupted the microtubule, which is involved in autophagosome formation, and this disruption was milder in the Chop-/- than Chop+/+ mouse kidney, with less reduction of histone deacetylase 6 and αtubulin acetyl transferase, which acetylates tubulin, a component of the microtubule. After UUO, apoptosis, a consequence of autophagy and mitochondrial damage, was reduced in the Chop-/- mouse kidney cells than in Chop+/+ mice. Thus, the ablation of Chop attenuates renal fibrosis, accompanied by reduced autophagy, mitochondrial fragmentation, microtubule disruption, and apoptosis. Overall, these results suggest that CHOP plays a critical role in the progression of kidney fibrosis, likely through regulation of autophagy and apoptosis.
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Apoptosis , Autofagia , Enfermedades Renales , Microtúbulos/metabolismo , Factor de Transcripción CHOP , Obstrucción Ureteral , Animales , Fibrosis , Enfermedades Renales/genética , Enfermedades Renales/metabolismo , Enfermedades Renales/patología , Ratones , Ratones Noqueados , Microtúbulos/genética , Microtúbulos/patología , Factor de Transcripción CHOP/genética , Factor de Transcripción CHOP/metabolismo , Obstrucción Ureteral/genética , Obstrucción Ureteral/metabolismo , Obstrucción Ureteral/patologíaRESUMEN
Mitochondrial NADP+-dependent isocitrate dehydrogenase (IDH2) catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate, synthesizing NADPH, which is essential for mitochondrial redox balance. Ischemia-reperfusion (I/R) is one of most common causes of AKI. I/R disrupts the mitochondrial redox balance, resulting in oxidative damage to mitochondria and cells. Here, we investigated the role of IDH2 in I/R-induced AKI. I/R injury in mice led to the inactivation of IDH2 in kidney tubule cells. Idh2 gene deletion exacerbated the I/R-induced increase in plasma creatinine and BUN levels and the histologic evidence of tubule injury, and augmented the reduction of NADPH levels and the increase in oxidative stress observed in the kidney after I/R. Furthermore, Idh2 gene deletion exacerbated I/R-induced mitochondrial dysfunction and morphologic fragmentation, resulting in severe apoptosis in kidney tubule cells. In cultured mouse kidney proximal tubule cells, Idh2 gene downregulation enhanced the mitochondrial damage and apoptosis induced by treatment with hydrogen peroxide. This study demonstrates that Idh2 gene deletion exacerbates mitochondrial damage and tubular cell death via increased oxidative stress, suggesting that IDH2 is an important mitochondrial antioxidant enzyme that protects cells from I/R insult.
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Muerte Celular , Isocitrato Deshidrogenasa/deficiencia , Túbulos Renales/patología , Riñón/irrigación sanguínea , Riñón/enzimología , Mitocondrias/enzimología , Daño por Reperfusión/enzimología , Lesión Renal Aguda/enzimología , Lesión Renal Aguda/etiología , Animales , Apoptosis , Células Cultivadas , Eliminación de Gen , Isocitrato Deshidrogenasa/genética , Masculino , Ratones , Ratones NoqueadosRESUMEN
C/EBP homologous protein (CHOP), a transcription factor for the expression of apoptosis-related genes, plays an important role in endoplasmic reticulum (ER) stress-related organ diseases, including diseases of the kidney. Here, we investigated the role of CHOP in ischemia/reperfusion (I/R)-induced acute kidney injury using CHOP-knockout (CHOP(-/-)) and wild type (CHOP(+/+)) mice. Fifteen or thirty minutes of bilateral renal ischemia (I/R) insult resulted in necrotic and apoptotic tubular epithelial cell death, together with increases in plasma creatinine (PCr) and blood urea nitrogen (BUN) concentrations. After I/R, BiP/GRP78 and CHOP expressions in the kidney gradually increased over time. CHOP expression was greater in the outer medulla than that in the cortex and localized intensely in the nucleus. I/R caused apoptosis of tubular epithelial cells in both CHOP(-/-) and CHOP(+/+) mice. The number of apoptotic cells after I/R was lower in CHOP(-/-) mice than that in CHOP(+/+) mice. Consistent with the degree of apoptosis, I/R-induced kidney morphological and functional damages were milder in CHOP(-/-) than that in CHOP(+/+) mice. The cleavage of procaspase-3 and the induction of Bax protein after I/R were lower in CHOP(-/-) than that in CHOP(+/+) mice. In contrast, the expression levels of Bcl-2, Bcl-xL, cIAP2, Mcl-1, and XIAP were higher in CHOP(-/-) than that in CHOP(+/+) mice. These results indicate that I/R induces ER stress, leading to the activation of CHOP-associated apoptosis signals, resulting in renal functional and histological damages.
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Runt-related transcription factor 2 (Runx2) plays an important role in bone formation and de novo synthesis of proteins, including type 1 collagen. Runx2 has a potent effect on signaling of transforming growth factor (TGF)-ß and vice versa, implicating its significant role in fibrosis. Chronic renal failure comprises fibrosis, characterized as an increase in TGF-ß signaling, and expression of α-smooth muscle actin (α-SMA), and extracellular matrix proteins. Here, we evaluated the role of Runx2 in ureteral obstruction (UO)-induced kidney fibrosis using mice whose Runx2 gene expression is genetically down-regulated. UO caused tubular atrophy and dilation, expansion of interstitium, and increased expression of collagens and α-SMA with a concomitant decrease in expression of Runx2. Deficiency of Runx2 gene (Runx2(+/-) mice) showed higher expression of collagens and α-SMA in the kidney following UO compared to wild type (Runx2(+/+)) mice. UO-induced activation of TGF-ß signaling was higher in the Runx2(+/-) kidney than Runx2(+/+) kidney, suggesting an inhibitory effect of Runx2 on TGF-ß signaling in kidney fibrosis. Besides, overexpression of the Runx2 gene using an adenoviral vector in kidney tubule cells resulted in attenuated TGF-ß-induced Smad3 phosphorylation and expressions of α-SMA and collagen I. Furthermore, Runx2 gene deficient mouse embryonic fibroblasts induced greater activation of Smad3 and expression of α-SMA in response to TGF-ß. Collectively, Runx2 plays a protective role in UO-induced kidney fibrosis by inhibition of TGF-ß signaling, suggesting Runx2 as a novel target for protection against fibrosis-related diseases such as chronic renal failure.
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Subunidad alfa 1 del Factor de Unión al Sitio Principal/genética , Fibrosis/etiología , Enfermedades Renales/etiología , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Obstrucción Ureteral/genética , Animales , Secuencia de Bases , Línea Celular , Cartilla de ADN , Perros , Fibrosis/genética , Enfermedades Renales/genética , Masculino , Ratones , Obstrucción Ureteral/complicacionesRESUMEN
BACKGROUND/AIM: Angiotensinogen (AGT), a precursor of angiotensin II (AngII), contributes to regulating (patho)physiological conditions, including blood pressure changes, inflammation, and kidney fibrosis. However, the precise role of tissue-specific AGT in kidney fibrosis independent of blood pressure remains to be fully understood. This study investigated the source of intrarenal AGT and its role in kidney injury and fibrosis during obstructive nephropathy. MATERIALS AND METHODS: Proximal tubule- (PT, major source secreting AGT in the kidney; PKO) or liver- (major source of circulating AGT; LKO) AGT knockout (KO) mice were subjected to unilateral ureteral obstruction (UUO), a blood pressure-independent fibrosis model. RESULTS: UUO increased AGT mRNA and protein levels in the kidneys. PKO decreased AGT mRNA, but LKO enhanced it in UUO kidneys compared with the control. In contrast, the intrarenal protein levels of AGT increased in PKO, but not in LKO in UUO kidneys, indicating that the liver is a major source of intrarenal AGT protein. Expression of megalin, a PT receptor involved in the uptake of circulating AGT, was down-regulated in UUO kidneys and was independent of PKO or LKO. However, none of these changes prevented UUO-induced tubular injury and kidney fibrosis. CONCLUSION: Hepatic and proximal tubule AGT play distinct roles in contributing to intrarenal AGT levels during UUO, and their genetic inhibitions fail to prevent kidney injury and fibrosis, suggesting a highly complicated signaling pathway of the renin-angiotensin system and an associated compensatory mechanism in obstructive nephropathy.
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Angiotensinógeno , Modelos Animales de Enfermedad , Fibrosis , Riñón , Ratones Noqueados , Obstrucción Ureteral , Animales , Ratones , Angiotensinógeno/metabolismo , Angiotensinógeno/genética , Riñón/metabolismo , Riñón/patología , Enfermedades Renales/metabolismo , Enfermedades Renales/etiología , Enfermedades Renales/patología , Enfermedades Renales/genética , Túbulos Renales Proximales/metabolismo , Túbulos Renales Proximales/patología , Hígado/metabolismo , Hígado/patología , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad/genética , Obstrucción Ureteral/metabolismo , Obstrucción Ureteral/complicaciones , Obstrucción Ureteral/genética , Obstrucción Ureteral/patologíaRESUMEN
The primary cilium is a microtubule-based nonmotile organelle that extends from the surface of cells, including renal tubular cells. Here, we investigated the alteration of primary cilium length during epithelial cell injury and repair, following ischemia/reperfusion (I/R) insult, and the role of reactive oxygen species in this alteration. Thirty minutes of bilateral renal ischemia induced severe renal tubular cell damage and an increase of plasma creatinine (PCr) concentration. Between 8 and 16 days following the ischemia, the increased PCr returned to normal range, although without complete histological restoration. Compared with the primary cilium length in normal kidney tubule cells, the length was shortened 4 h and 1 day following ischemia, increased over normal 8 days after ischemia, and then returned to near normal 16 days following ischemia. In the urine of I/R-subjected mice, acetylated tubulin was detected. The cilium length of proliferating cells was shorter than that in nonproliferating cells. Mature cells had shorter cilia than differentiating cells. Treatment with Mn(III) tetrakis(1-methyl-4-pyridyl) porphyrin (MnTMPyP), an antioxidant, during the recovery of damaged kidneys accelerated normalization of cilia length concomitant with a decrease of oxidative stress and morphological recovery in the kidney. In the Madin-Darby canine kidney (MDCK) cells, H(2)O(2) treatment caused released ciliary fragment into medium, and MnTMPyP inhibited the deciliation. The ERK inhibitor U0126 inhibited elongation of cilia in normal and MDCK cells recovering from H(2)O(2) stress. Taken together, our results suggest that primary cilia length reflects cell proliferation and the length of primary cilium is regulated, at least, in part, by reactive oxygen species through ERK.
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Cilios/metabolismo , Células Epiteliales/metabolismo , Isquemia/metabolismo , Riñón/irrigación sanguínea , Estrés Oxidativo/fisiología , Animales , Línea Celular , Cilios/efectos de los fármacos , Cilios/patología , Perros , Células Epiteliales/efectos de los fármacos , Células Epiteliales/patología , Isquemia/patología , Riñón/efectos de los fármacos , Riñón/metabolismo , Riñón/patología , Metaloporfirinas/farmacología , Ratones , Estrés Oxidativo/efectos de los fármacos , Especies Reactivas de Oxígeno/metabolismo , Daño por Reperfusión/metabolismo , Daño por Reperfusión/patologíaRESUMEN
The kidney is a highly metabolic organ and uses high levels of ATP to maintain electrolyte and acid-base homeostasis and reabsorb nutrients. Energy depletion is a critical factor in development and progression of various kidney diseases including acute kidney injury (AKI), chronic kidney disease (CKD), and diabetic and glomerular nephropathy. Mitochondrial fatty acid ß-oxidation (FAO) serves as the preferred source of ATP in the kidney and its dysfunction results in ATP depletion and lipotoxicity to elicit tubular injury and inflammation and subsequent fibrosis progression. This review explores the current state of knowledge on the role of mitochondrial FAO dysfunction in the pathophysiology of kidney diseases including AKI and CKD and prospective views on developing therapeutic interventions based on mitochondrial energy metabolism.
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The development of hypertension is associated with mitochondrial redox balance disruptions. NADP+-dependent isocitrate dehydrogenase 2 (IDH2) plays an important role in the maintenance of mitochondrial redox balance by producing mitochondrial NADPH, which is an essential cofactor in the reduction of glutathione (from GSSG to GSH) to reduced form of glutathione (GSH). We investigated the association of IDH2 between the development of prolonged high-fat diet (HFD)-induced hypertension. Idh2 gene-deleted (Idh2-/-) male mice and wild-type (Idh2+/+) littermates were fed either HFD or low-fat diet (LFD). Some mice were administrated with Mito-TEMPO, a mitochondria-specific antioxidant. HFD feeding increased blood pressure (BP) in both Idh2-/- mice and Idh2+/+ mice. HFD-induced BP increase was greater in Idh2-/- than Idh2+/+ mice. HFD intake decreased IDH2 activity, NADPH levels, and the GSH/(GSH + GSSG) ratio in the renal mitochondria. However, HFD intake increased mitochondrial ROS levels, along with the accompanying oxidative stress and damage. HFD intake increased angiotensin II receptor 1 type 1 mRNA levels in the kidneys and plasma renin and angiotensin II concentrations. These HFD-induced changes were more prominent in Idh2-/- mice than Idh2+/+ mice. Mito-TEMPO mitigated the HFD-induced changes in both Idh2-/- and Idh2+/+ mice, with greater effects in Idh2-/- mice than Idh2+/+ mice. These results indicate that prolonged HFD intake disrupts the IDH2-NADPH-GSH-associated antioxidant system and activates the renin-angiotensin system in the kidney, leading to increased BP, suggesting that IDH2 is a critical enzyme in the development of hypertension and that the IDH2-associated antioxidant system could serve as a potential hypertension treatment target.
Asunto(s)
Hipertensión , Isocitrato Deshidrogenasa , Animales , Apoptosis , Dieta Alta en Grasa/efectos adversos , Hipertensión/genética , Isocitrato Deshidrogenasa/genética , Isocitrato Deshidrogenasa/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Estrés OxidativoRESUMEN
AIMS: Methionine sulfoxide reductase A (MsrA), which is abundantly localized in the mitochondria, reduces methionine-S-sulfoxide, scavenging reactive oxygen species (ROS). Cisplatin, an anticancer drug, accumulates at high levels in the mitochondria of renal cells, causing mitochondrial impairment that ultimately leads to nephrotoxicity. Here, we investigated the role of MsrA in cisplatin-induced mitochondrial damage and kidney cell death using MsrA gene-deleted (MsrA-/-) mice. RESULTS: Cisplatin injection resulted in increases of ROS production, methionine oxidation, and oxidative damage in the kidneys. This oxidative stress was greater in MsrA-/- mouse kidneys than in wild-type (MsrA+/+) mouse kidneys. MsrA gene deletion exacerbated cisplatin-induced reductions in the expression and activity of MsrA and MsrBs, and the expression of thioredoxin 1, glutathione peroxidase 1 and 4, mitochondrial superoxide dismutase, cystathionine-ß-synthase, and cystathionine-γ-lyase. Cisplatin induced swelling, cristae loss, and fragmentation of mitochondria with increased lipid peroxidation, more so in MsrA-/- than in MsrA+/+ kidneys. The ratio of mitochondrial fission regulator (Fis1) to fusion regulator (Opa1) was higher in MsrA-/- than MsrA+/+ mice. MsrA deletion exacerbated cisplatin-induced increases in Bax to Bcl-2 ratio, cleaved caspase-3 level, and apoptosis, whereas MsrA overexpression attenuated cisplatin-induced oxidative stress and apoptosis. INNOVATION: MsrA gene deletion in mice exacerbates cisplatin-induced renal injury through increases of mitochondrial susceptibility, whereas MsrA overexpression protects cells against cisplatin. CONCLUSION: This study demonstrates that MsrA protects kidney cells against cisplatin-induced methionine oxidation, oxidative stress, mitochondrial damage, and apoptosis, suggesting that MsrA could be a useful target protein for the treatment of cisplatin-induced nephrotoxicity. Antioxid. Redox Signal. 27, 727-741.
Asunto(s)
Lesión Renal Aguda/genética , Cisplatino/toxicidad , Metionina Sulfóxido Reductasas/genética , Mitocondrias/efectos de los fármacos , Lesión Renal Aguda/inducido químicamente , Lesión Renal Aguda/metabolismo , Animales , Muerte Celular , Línea Celular , Modelos Animales de Enfermedad , GTP Fosfohidrolasas/metabolismo , Genu Valgum , Metionina/metabolismo , Metionina Sulfóxido Reductasas/deficiencia , Ratones , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , Estrés OxidativoRESUMEN
Cystathionine γ-lyase (CSE), the last key enzyme of the transsulfuration pathway, is involved in the production of hydrogen sulfide (H2S) and glutathione (GSH), which regulate redox balance and act as important antioxidant molecules. Impairment of the H2S- and GSH-mediated antioxidant system is associated with the progression of chronic kidney disease (CKD), characterized by kidney fibrosis and dysfunction. Here, we evaluated the role of CSE in the progression of kidney fibrosis after unilateral ureteral obstruction (UUO) using mice deficient in the Cse gene. UUO of wild-type mice reduced the expression of H2S-producing enzymes, CSE, cystathionine ß-synthase, and 3-mercaptopyruvate sulfurtransferase in the obstructed kidneys, resulting in decreased H2S and GSH levels. Cse gene deletion lowered H2S and GSH levels in the kidneys. Deleting the Cse gene exacerbated the decrease in H2S and GSH levels and increase in superoxide formation and oxidative damage to proteins, lipids, and DNA in the kidneys after UUO, which were accompanied by greater kidney fibrosis, deposition of extracellular matrixes, expression of α-smooth muscle actin, tubular damage, and infiltration of inflammatory cells. Furthermore, Cse gene deletion exacerbated mitochondrial fragmentation and apoptosis of renal tubule cells after UUO. The data provided herein constitute in vivo evidence that Cse deficiency impairs renal the H2S- and GSH-producing activity and exacerbates UUO-induced kidney fibrosis. These data propose a novel therapeutic approach against CKD by regulating CSE and the transsulfuration pathway.
Asunto(s)
Cistationina gamma-Liasa/genética , Glutatión/biosíntesis , Sulfuro de Hidrógeno/metabolismo , Insuficiencia Renal Crónica/genética , Obstrucción Ureteral/genética , Actinas/genética , Actinas/metabolismo , Animales , Cistationina betasintasa/genética , Cistationina betasintasa/metabolismo , Cistationina gamma-Liasa/deficiencia , Progresión de la Enfermedad , Células Epiteliales/enzimología , Células Epiteliales/patología , Femenino , Fibrosis , Regulación de la Expresión Génica , Riñón/enzimología , Riñón/patología , Túbulos Renales/enzimología , Túbulos Renales/patología , Ratones , Ratones Noqueados , Mitocondrias/metabolismo , Mitocondrias/patología , Oxidación-Reducción , Insuficiencia Renal Crónica/enzimología , Insuficiencia Renal Crónica/patología , Transducción de Señal , Sulfurtransferasas/genética , Sulfurtransferasas/metabolismo , Superóxidos/metabolismo , Obstrucción Ureteral/enzimología , Obstrucción Ureteral/patologíaRESUMEN
Neuron-derived orphan receptor (NOR-1) is a member of the thyroid/steroid receptor superfamily that was originally identified in forebrain neuronal cells undergoing apoptosis. In addition to apoptotic stimuli, activation of several signal transduction pathways including direct neuronal depolarization regulates the expression of NOR-1. In this study we tested whether the expression of NOR-1 is changed following transient ischemic injury in the adult rat brain. NOR-1 mRNA increased rapidly in the dentate gyrus of the hippocampal formation and piriform cortex 3 h after transient global ischemia and returned to basal level at 6 h. On the other hand, oxygen-glucose deprivation of cultured cerebral cortical neurons did not alter the expression of NOR-1. These results suggest that expression of NOR-1 is differentially regulated in different brain regions in response to globally applied brain ischemia, but that hypoxia is not sufficient to induce its expression.