Advanced Oxidation Protein Products Contribute to Chronic-Kidney-Disease-Induced Adipose Inflammation through Macrophage Activation.

Fat atrophy and adipose tissue inflammation can cause the pathogenesis of metabolic symptoms in chronic kidney disease (CKD). During CKD, the serum levels of advanced oxidation protein products (AOPPs) are elevated. However, the relationship between fat atrophy/adipose tissue inflammation and AOPPs has remained unknown. The purpose of this study was to investigate the involvement of AOPPs, which are known as uremic toxins, in adipose tissue inflammation and to establish the underlying molecular mechanism. In vitro studies involved co-culturing mouse-derived adipocytes (differentiated 3T3-L1) and macrophages (RAW264.7). In vivo studies were performed using adenine-induced CKD mice and AOPP-overloaded mice. Fat atrophy, macrophage infiltration and increased AOPP activity in adipose tissue were identified in adenine-induced CKD mice. AOPPs induced MCP-1 expression in differentiated 3T3-L1 adipocytes via ROS production. However, AOPP-induced ROS production was suppressed by the presence of NADPH oxidase inhibitors and the scavengers of mitochondria-derived ROS. A co-culturing system showed AOPPs induced macrophage migration to adipocytes. AOPPs also up-regulated TNF-α expression by polarizing macrophages to an M1-type polarity, and then induced macrophage-mediated adipose inflammation. In vitro data was supported by experiments using AOPP-overloaded mice. AOPPs contribute to macrophage-mediated adipose inflammation and constitute a potential new therapeutic target for adipose inflammation associated with CKD.

Indoxyl Sulfate Contributes to mTORC1-Induced Renal Fibrosis via The OAT/NADPH Oxidase/ROS Pathway.

Activation of mTORC1 (mechanistic target of rapamycin complex 1) in renal tissue has been reported in chronic kidney disease (CKD)-induced renal fibrosis. However, the molecular mechanisms responsible for activating mTORC1 in CKD pathology are not well understood. The purpose of this study was to identify the uremic toxin involved in mTORC1-induced renal fibrosis. Among the seven protein-bound uremic toxins, only indoxyl sulfate (IS) caused significant activation of mTORC1 in human kidney 2 cells (HK-2 cells). This IS-induced mTORC1 activation was inhibited in the presence of an organic anion transporter inhibitor, a NADPH oxidase inhibitor, and an antioxidant. IS also induced epithelial-mesenchymal transition of tubular epithelial cells (HK-2 cells), differentiation of fibroblasts into myofibroblasts (NRK-49F cells), and inflammatory response of macrophages (THP-1 cells), which are associated with renal fibrosis, and these effects were inhibited in the presence of rapamycin (mTORC1 inhibitor). In in vivo experiments, IS overload was found to activate mTORC1 in the mouse kidney. The administration of AST-120 or rapamycin targeted to IS or mTORC1 ameliorated renal fibrosis in Adenine-induced CKD mice. The findings reported herein indicate that IS activates mTORC1, which then contributes to renal fibrosis. Therapeutic interventions targeting IS and mTORC1 could be effective against renal fibrosis in CKD.

Advanced oxidation protein products contribute to chronic kidney disease-induced muscle atrophy by inducing oxidative stress via CD36/NADPH oxidase pathway.

BACKGROUND: Sarcopenia with chronic kidney disease (CKD) progression is associated with life prognosis. Oxidative stress has attracted interest as a trigger for causing CKD-related muscular atrophy. Advanced oxidation protein products (AOPPs), a uraemic toxin, are known to increase oxidative stress. However, the role of AOPPs on CKD-induced muscle atrophy remains unclear. METHODS: In a retrospective case-control clinical study, we evaluated the relationship between serum AOPPs levels and muscle strength in haemodialysis patients with sarcopenia (n = 26, mean age ± SEM: 78.5 ± 1.4 years for male patients; n = 22, mean age ± SEM: 79.1 ± 1.5 for female patients), pre-sarcopenia (n = 12, mean age ± SEM: 73.8 ± 2.0 years for male patients; n = 4, mean age ± SEM: 74.3 ± 4.1 for female patients) or without sarcopenia (n = 12, mean age ± SEM: 71.3 ± 1.6 years for male patients; n = 7, mean age ± SEM: 77.7 ± 1.6 for female ). The molecular mechanism responsible for the AOPPs-induced muscle atrophy was investigated by using 5/6-nephrectomized CKD mice, AOPPs-overloaded mice, and C2C12 mouse myoblast cells. RESULTS: The haemodialysis patients with sarcopenia showed higher serum AOPPs levels as compared with the patients without sarcopenia. The serum AOPPs levels showed a negative correlation with grip strength (P < 0.01 for male patients, P < 0.01 for female patients) and skeletal muscle index (P < 0.01 for male patients). Serum AOPPs levels showed a positive correlation with cysteinylated albumin (Cys-albumin), a marker of oxidative stress (r2  = 0.398, P < 0.01). In the gastrocnemius of CKD mice, muscle AOPPs levels were also increased, and it showed a positive correlation with atrogin-1 (r2  = 0.538, P < 0.01) and myostatin expression (r2  = 0.421, P < 0.05), but a negative correlation with PGC-1α expression (r2  = 0.405, P < 0.05). Using C2C12 cells, AOPPs increased atrogin-1 and myostatin expression through the production of reactive oxygen species via CD36/NADPH oxidase pathway, and decreased myotube formation. AOPPs also induced mitochondrial dysfunction. In the AOPPs-overloaded mice showed that decreasing running time and hanging time accompanied by increasing AOPPs levels and decreasing cross-sectional area in gastrocnemius. CONCLUSIONS: Advanced oxidation protein products contribute to CKD-induced sarcopenia, suggesting that AOPPs or its downstream signalling pathway could be a therapeutic target for the treatment of CKD-induced sarcopenia. Serum AOPPs or Cys-albumin levels could be a new diagnostic marker for sarcopenia in CKD.

An acute phase protein α1-acid glycoprotein mitigates AKI and its progression to CKD through its anti-inflammatory action.

The molecular mechanism for acute kidney injury (AKI) and its progression to chronic kidney disease (CKD) continues to be unclear. In this study, we investigated the pathophysiological role of the acute phase protein α1-acid glycoprotein (AGP) in AKI and its progression to CKD using AGP KO mice. Plasma AGP levels in WT mice were increased by about 3.5-fold on day 1-2 after renal ischemia-reperfusion (IR), and these values then gradually decreased to the level before renal IR on day 7-14. On day 1 after renal IR, the AGP KO showed higher renal dysfunction, tubular injury and renal inflammation as compared with WT. On day 14, renal function, tubular injury and renal inflammation in WT had recovered, but the recovery was delayed, and renal fibrosis continued to progress in AGP KO. These results obtained from AGP KO were rescued by the administration of human-derived AGP (hAGP) simultaneously with renal IR. In vitro experiments using RAW264.7 cells showed hAGP treatment suppressed the LPS-induced macrophage inflammatory response. These data suggest that endogenously induced AGP in early renal IR functions as a renoprotective molecule via its anti-inflammatory action. Thus, AGP represents a potential target molecule for therapeutic development in AKI and its progression CKD.

Effect of Cinacalcet on the Redox Status of Albumin in Secondary Hyperparathyroidism Patients Receiving Hemodialysis.

Chronic kidney disease (CKD) patients with secondary hyperparathyroidism (SHPT) have an increased risk of cardiovascular disease (CVD). Cinacalcet is a calcimimetic that permits impaired endothelial functions to be recovered via inhibiting parathyroid hormone (PTH) production in SHPT patients. However, the underlying mechanism for its action remains unknown. The purpose of this study was to examine the effect of cinacalcet on the redox state of human serum albumin (HSA), a reliable marker for assessing endothelial oxidative damage in SHPT patients who were receiving hemodialysis. Cinacalcet was administered to six SHPT patients for a period of 8 weeks. After 4 weeks of treatment, cinacalcet significantly decreased the oxidized albumin ratio which is a ratio of reduced and oxidized forms of HSA via increasing reduced form of HSA. Moreover, the radical scavenging abilities of HSA that was isolated from SHPT patients were increased by cinacalcet, suggesting the recovery of the impaired vascular anti-oxidant ability. Interestingly, the oxidized albumin ratio in SHPT patients was significantly higher than that in hemodialysis patients. In addition, the changes of intact PTH levels were significantly correlated with the oxidized albumin ratio. It therefore appears that PTH may induce oxidative stress in SHPT patients. In fact, an active analogue of PTH increased the production of reactive oxygen species in human endothelial cells. Thus, cinacalcet exhibits anti-oxidative activity through its pharmacological action. Additionally, cinacalcet itself showed radical scavenging activity. In conclusion, cinacalcet improves the redox status of HSA by inhibiting PTH production and partially by its radical scavenging action.

Indoxyl Sulfate Contributes to Adipose Tissue Inflammation through the Activation of NADPH Oxidase.

Adipose tissue inflammation appears to be a risk factor for the progression of chronic kidney disease (CKD), but the effect of CKD on adipose tissue inflammation is poorly understood. The purpose of this study was to clarify the involvement of uremic toxins (indoxyl sulfate (IS), 3-indoleacetic acid, p-cresyl sulfate and kynurenic acid) on CKD-induced adipose tissue inflammation. IS induces monocyte chemoattractant protein-1 (MCP-1) expression and reactive oxygen species (ROS) production in the differentiated 3T3L-1 adipocyte. An organic anion transporter (OAT) inhibitor, an NADPH oxidase inhibitor or an antioxidant suppresses the IS-induced MCP-1 expression and ROS production, suggesting the OAT/NADPH oxidase/ROS pathway is involved in the action of IS. Co-culturing 3T3L-1 adipocytes and mouse macrophage cells showed incubating adipocytes with IS increased macrophage infiltration. An IS-overload in healthy mice increased IS levels, oxidative stress and MCP-1 expression in epididymal adipose tissue compared to unloaded mice. Using 5/6-nephrectomized mice, the administration of AST-120 suppressed oxidative stress and the expression of MCP-1, F4/80 and TNF-α in epididymal adipose tissue. These collective data suggest IS could be a therapeutic target for the CKD-related inflammatory response in adipose tissue, and that AST-120 could be useful for the treatment of IS-induced adipose tissue inflammation.

A synthetic retinoic acid receptor agonist Am80 ameliorates renal fibrosis via inducing the production of alpha-1-acid glycoprotein.

Renal fibrosis is a major factor in the progression of chronic kidney disease and the final common pathway of kidney injury. Therefore, the effective therapies against renal fibrosis are urgently needed. The objective of this study was to investigate the effect of Am80, a synthetic retinoic acid receptor (RAR) agonist, in the treatment of renal interstitial fibrosis using unilateral ureteral obstruction (UUO) mice. The findings indicate that Am80 treatment suppressed renal fibrosis and inflammation to the same degree as the naturally-occuring retinoic acid, all-trans retinoic acid (atRA). But the adverse effect of body weight loss in Am80-treated mice was lower compared to the atRA treatment. The hepatic mRNA levels of alpha-1-acid glycoprotein (AGP), a downstream molecule of RAR agonist, was increased following administration of Am80 to healthy mice. In addition, increased AGP mRNA expression was also observed in HepG2 cells and THP-1-derived macrophages that had been treated with Am80. AGP-knockout mice exacerbated renal fibrosis, inflammation and macrophage infiltration in UUO mice, indicating endogenous AGP played an anti-fibrotic and anti-inflammatory role during the development of renal fibrosis. We also found that no anti-fibrotic effect of Am80 was observed in UUO-treated AGP-knockout mice whereas atRA treatment tended to show a partial anti-fibrotic effect. These collective findings suggest that Am80 protects against renal fibrosis via being involved in AGP function.

α1-Acid Glycoprotein Attenuates Adriamycin-Induced Nephropathy via CD163 Expressing Macrophage Induction.

Background: Recent clinical studies have shown that proteinuria is a critical factor in the progression of CKD and onset of cardiovascular disease. Inflammation and infiltration of macrophages into renal tissue are implicated as causes of proteinuria. α1-Acid glycoprotein (AGP), an acute-phase plasma protein, is leaked into the urine in patients with proteinuria. However, the relationship between urinary leakage of AGP, renal inflammation, and proteinuria remains unclear. Methods: Human AGP (hAGP) was exogenously administrated for 5 consecutive days to adriamycin-induced nephropathy model mice. Results: Adriamycin treatment increased urinary AGP, accompanied by decreased plasma AGP in mice. Exogenous hAGP administration to adriamycin-treated mice suppressed proteinuria, renal histologic injury, and inflammation. hAGP administration increased renal CD163 expression, a marker of anti-inflammatory macrophages. Similar changes were observed in PMA-differentiated THP-1 cells treated with hAGP. Even in the presence of LPS, hAGP treatment increased CD163/IL-10 expression in differentiated THP-1 cells. Conclusions: AGP alleviates proteinuria and renal injury in mice with proteinuric kidney disease via induction of CD163-expressing macrophages with anti-inflammatory function. The results demonstrate that endogenous AGP could work to protect against glomerular disease. Thus, AGP supplementation could be a possible new therapeutic intervention for patients with glomerular disease.

Advanced Oxidation Protein Products Contribute to Renal Tubulopathy via Perturbation of Renal Fatty Acids.

Background: Renal proximal tubulopathy plays a crucial role in kidney disease, but its molecular mechanism is incompletely understood. Because proximal tubular cells consume a lot of energy during reabsorption, the relationship between fatty acids (FAs) and proximal tubulopathy has been attracting attention. The purpose of this study is to investigate the association between change in renal FA composition and tubulopathy. Methods: Mice with cisplatin-induced nephrotoxicity were used as a model of AKI and 5/6-nephrectomized mice were used as a model of CKD. Renal FA composition in mice was measured by GC-MS. Human tubular epithelial cells (HK-2 cells) were used for in vitro studies. Results: In kidneys of AKI mice, increased stearic acid (C18:0) and decreased palmitic acid (C16:0) were observed, accompanied by increased expression of the long-chain FA elongase Elovl6. Similar results were also obtained in CKD mice. We show that C18:0 has higher tubular toxicity than C16:0 via induction of ER stress. Using adenovirus-expressing Elovl6 or siRNA for Elovl6 in HK-2 cells, we demonstrated that increased Elovl6 expression contributes to tubulopathy via increasing C18:0. Elovl6 knockout suppressed the increased serum creatinine levels, renal ER stress, and inflammation that would usually result after 5/6 nephrectomy. Advanced oxidation protein products (AOPPs), specifically an oxidized albumin, was found to induce Elovl6 via the mTORC1/SREBP1 pathway. Conclusions: AOPPs may contribute to renal tubulopathy via perturbation of renal FAs through induction of Elovl6. The perturbation of renal FAs induced by the AOPPs-Elovl6 system could be a potential target for the treatment of tubulopathy.

A downstream molecule of 1,25-dihydroxyvitamin D3, alpha-1-acid glycoprotein, protects against mouse model of renal fibrosis.

Renal fibrosis, the characteristic feature of progressive chronic kidney disease, is associated with unremitting renal inflammation. Although it is reported that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D, elicits an anti-renal fibrotic effect, its molecular mechanism is still unknown. In this study, renal fibrosis and inflammation observed in the kidney of unilateral ureteral obstruction (UUO) mice were reduced by the treatment of 1,25(OH)2D3. The plasma protein level of alpha-1-acid glycoprotein (AGP), a downstream molecule of 1,25(OH)2D3, was increased following administration of 1,25(OH)2D3. Additionally, increased mRNA expression of ORM1, an AGP gene, was observed in HepG2 cells and THP-1-derived macrophages that treated with 1,25(OH)2D3. To investigate the involvement of AGP, exogenous AGP was administered to UUO mice, resulting in attenuated renal fibrosis and inflammation. We also found the mRNA expression of CD163, a monocyte/macrophage marker with anti-inflammatory potential, was increased in THP-1-derived macrophages under stimulus from 1,25(OH)2D3 or AGP. Moreover, AGP prevented lipopolysaccharide-induced macrophage activation. Thus, AGP could be a key molecule in the protective effect of 1,25(OH)2D3 against renal fibrosis. Taken together, AGP may replace vitamin D to function as an important immune regulator, offering a novel therapeutic strategy for renal inflammation and fibrosis.

Parathyroid hormone contributes to the down-regulation of cytochrome P450 3A through the cAMP/PI3K/PKC/PKA/NF-κB signaling pathway in secondary hyperparathyroidism.

Chronic kidney disease (CKD), which affects, not only renal clearance, but also non-renal clearance, is accompanied by a decline in renal function. Although it has been suggested that humoral factors, such as uremic toxins that accumulate in the body under CKD conditions, could be involved in the changes associated with non-renal drug clearance, the overall process is not completely understood. In this study, we report on the role of parathyroid hormone (PTH), a middle molecule uremic toxin, on the expression of drug metabolizing or transporting proteins using rats with secondary hyperparathyroidism (SHPT) as models. In SHPT rats, hepatic and intestinal CYP3A expression was suppressed, but the changes were recovered by the administration of the calcimimetic cinacalcet, a PTH suppressor. Under the same experimental conditions, a pharmacokinetic study using orally administered midazolam, a substrate for CYP3A, showed that the AUC was increased by 5 times in SHPT rats, but that was partially recovered by a cinacalcet treatment. This was directly tested in rat primary hepatocytes and intestinal Caco-2 cells where the expression of the CYP3A protein was down-regulated by PTH (1-34). In Caco-2 cells, PTH (1-34) down-regulated the expression of CYP3A mRNA, but an inactive PTH derivative (13-34) had no effect. 8-Bromo-cyclic adenosine monophosphate, a membrane-permeable cAMP analog, reduced mRNA expression of CYP3A whereas the inhibitors of PI3K, NF-κB, PKC and PKA reversed the PTH-induced CYP3A down-regulation. These results suggest that PTH down-regulates CYP3A through multiple signaling pathways, including the PI3K/PKC/PKA/NF-κB pathway after the elevation of intracellular cAMP, and the effect of PTH can be prevented by cinacalcet treatment.

Potential therapeutic interventions for chronic kidney disease-associated sarcopenia via indoxyl sulfate-induced mitochondrial dysfunction.

BACKGROUND: Chronic kidney disease (CKD) patients experience skeletal muscle wasting and decreased exercise endurance. Our previous study demonstrated that indoxyl sulfate (IS), a uremic toxin, accelerates skeletal muscle atrophy. The purpose of this study was to examine the issue of whether IS causes mitochondria dysfunction and IS-targeted intervention using AST-120, which inhibits IS accumulation, or mitochondria-targeted intervention using L-carnitine or teneligliptin, a dipeptidyl peptidase-4 inhibitor which retains mitochondria function and alleviates skeletal muscle atrophy and muscle endurance in chronic kidney disease mice. METHODS: The in vitro effect of IS on mitochondrial status was evaluated using mouse myofibroblast cells (C2C12 cell). The mice were divided into sham or 5/6-nephrectomized (CKD) mice group. Chronic kidney disease mice were also randomly assigned to non-treatment group and AST-120, L-carnitine, or teneligliptin treatment groups. RESULTS: In C2C12 cells, IS induced mitochondrial dysfunction by decreasing the expression of PGC-1α and inducing autophagy in addition to decreasing mitochondrial membrane potential. Co-incubation with an anti-oxidant, ascorbic acid, L-carnitine, or teneligliptine restored the values to their original state. In CKD mice, the body and skeletal muscle weights were decreased compared with sham mice. Compared with sham mice, the expression of interleukin-6 and atrophy-related factors such as myostatin and atrogin-1 was increased in the skeletal muscle of CKD mice, whereas muscular Akt phosphorylation was decreased. In addition, a reduced exercise capacity was observed for the CKD mice, which was accompanied by a decreased expression of muscular PCG-1α and increased muscular autophagy, as reflected by decreased mitochondria-rich type I fibres. An AST-120 treatment significantly restored these changes including skeletal muscle weight observed in CKD mice to the sham levels accompanied by a reduction in IS levels. An L-carnitine or teneligliptin treatment also restored them to the sham levels without changing IS level. CONCLUSIONS: Our results indicate that IS induces mitochondrial dysfunction in skeletal muscle cells and provides a potential therapeutic strategy such as IS-targeted and mitochondria-targeted interventions for treating CKD-induced muscle atrophy and decreased exercise endurance.

Down-regulation of ABCG2, a urate exporter, by parathyroid hormone enhances urate accumulation in secondary hyperparathyroidism.

Hyperuricemia occurs with increasing frequency among patients with hyperparathyroidism. However, the molecular mechanism by which the serum parathyroid hormone (PTH) affects serum urate levels remains unknown. This was studied in uremic rats with secondary hyperparathyroidism where serum urate levels were found to be increased and urate excretion in the intestine and kidney decreased, presumably due to down-regulation of the expression of the urate exporter ABCG2 in intestinal and renal epithelial membranes. These effects were prevented by administration of the calcimimetic cinacalcet, a PTH suppressor, suggesting that PTH may down-regulate ABCG2 expression. This was directly tested in intestinal Caco-2 cells where the expression of ABCG2 on the plasma membrane was down-regulated by PTH (1-34) while its mRNA level remained unchanged. Interestingly, an inactive PTH derivative (13-34) had no effect, suggesting that a posttranscriptional regulatory system acts through the PTH receptor to regulate ABCG2 plasma membrane expression. As found in an animal study, additional clinical investigations showed that treatment with cinacalcet resulted in significant reductions in serum urate levels together with decreases in PTH levels in patients with secondary hyperparathyroidism undergoing dialysis. Thus, PTH down-regulates ABCG2 expression on the plasma membrane to suppress intestinal and renal urate excretion, and the effects of PTH can be prevented by cinacalcet treatment.

Effects of Secondary Hyperparathyroidism Treatment on Improvement in Anemia: Results from the MBD-5D Study.

OBJECTIVES: Anemia is an important prognostic factor in hemodialysis patients. It has been reported that parathyroidectomy ameliorates anemia and reduces the requirement of postoperative erythropoiesis-stimulating agents. The objective of this study was to assess the effect of cinacalcet, which is considered as a pharmacological parathyroidectomy, on anemia in hemodialysis patients. METHODS: We used data from a prospective cohort of Japanese hemodialysis patients with secondary hyperparathyroidism; the criteria were: intact parathyroid hormone concentrations ≥ 180 pg/mL or use of an intravenous or oral vitamin D receptor activator. All patients were cinacalcet-naïve at study enrollment. The main outcome measure was achievement of the target hemoglobin level (≥10.0 g/dL), which was measured repeatedly every 6 months. Cinacalcet exposure was defined as cumulative time since initiation. Both conventional longitudinal models and marginal structural models were adjusted for confounding factors. RESULTS: Among 3,201 cinacalcet-naïve individuals at baseline, cinacalcet was initiated in 1,337 individuals during the follow up. Cinacalcet users were slightly younger; included more patients with chronic glomerulonephritis and fewer with diabetes; were more likely to have a history of parathyroidectomy; and were more often on activated vitamin D agents, phosphate binders, and iron supplements. After adjusting for both time-invariant and time-varying potential confounders, including demographics, comorbidities, comedications, and laboratory values, each additional 6-month duration on cinacalcet was associated with a 1.1-fold increase in the odds of achieving the target hemoglobin level. CONCLUSIONS: Cinacalcet may improve anemia in chronic hemodialysis patients with secondary hyperparathyroidism, possibly through pathways both within and outside the parathyroid hormone pathways. Further investigations are warranted to delineate the roles of cinacalcet not only in the management of chronic kidney disease-mineral and bone disorder but also in anemia control.

Indoxyl sulfate potentiates skeletal muscle atrophy by inducing the oxidative stress-mediated expression of myostatin and atrogin-1.

Skeletal muscle atrophy, referred to as sarcopenia, is often observed in chronic kidney disease (CKD) patients, especially in patients who are undergoing hemodialysis. The purpose of this study was to determine whether uremic toxins are involved in CKD-related skeletal muscle atrophy. Among six protein-bound uremic toxins, indole containing compounds, indoxyl sulfate (IS) significantly inhibited proliferation and myotube formation in C2C12 myoblast cells. IS increased the factors related to skeletal muscle breakdown, such as reactive oxygen species (ROS) and inflammatory cytokines (TNF-α, IL-6 and TGF-ß1) in C2C12 cells. IS also enhanced the production of muscle atrophy-related genes, myostatin and atrogin-1. These effects induced by IS were suppressed in the presence of an antioxidant or inhibitors of the organic anion transporter and aryl hydrocarbon receptor. The administered IS was distributed to skeletal muscle and induced superoxide production in half-nephrectomized (1/2 Nx) mice. The chronic administration of IS significantly reduced the body weights accompanied by skeletal muscle weight loss. Similar to the in vitro data, IS induced the expression of myostatin and atrogin-1 in addition to increasing the production of inflammatory cytokines by enhancing oxidative stress in skeletal muscle. These data suggest that IS has the potential to accelerate skeletal muscle atrophy by inducing oxidative stress-mediated myostatin and atrogin-1 expression.

Effect of a Ferric Citrate Formulation, a Phosphate Binder, on Oxidative Stress in Chronic Kidney Diseases-Mineral and Bone Disorder Patients Receiving Hemodialysis: A Pilot Study.

A ferric citrate formulation for treating hyperphosphatemia is a new therapeutic that not only suppresses the accumulation of phosphorus in patients with chronic kidney disease-mineral bone disorders (CKD-MBD), but also ameliorates anemia caused by iron deficiency. In contrast, it has been demonstrated that intravenous iron injection markedly increases oxidative stress. This study was designed to investigate the effect of a ferric citrate formulation on oxidative stress in CKD-MBD patients receiving hemodialysis therapy. Fifteen CKD-MBD patients undergoing dialysis were enrolled in this study. The patients were orally administered a ferric citrate formulation for 6 months. Their plasma phosphorus concentrations remained unchanged with the switch from other phosphorus adsorbents to the ferric citrate formulation. In addition, the ferric citrate formulation generally allowed for dose reduction of an erythropoiesis stimulating agent with an increased hematopoietic effect. The average values of plasma ferritin level increased after the introduction of a ferric citrate formulation, but did not exceed 100 (ng/mL). Interestingly, oxidative stress markers did not increase significantly, and anti-oxidative capacity was not significantly decreased at 6 months after the drug administration. Similarly, no change was observed in any inflammation markers. The ferric citrate formulation induces negligible oxidative stress in CKD-MBD patients receiving dialysis under the present clinical condition.

p-Cresyl sulfate, a uremic toxin, causes vascular endothelial and smooth muscle cell damages by inducing oxidative stress.

The major cause of death in patients with chronic kidney disease (CKD) is cardiovascular disease. Here, p-Cresyl sulfate (PCS), a uremic toxin, is considered to be a risk factor for cardiovascular disease in CKD. However, our understanding of the vascular toxicity induced by PCS and its mechanism is incomplete. The purpose of this study was to determine whether PCS enhances the production of reactive oxygen species (ROS) in vascular endothelial and smooth muscle cells, resulting in cytotoxicity. PCS exhibited pro-oxidant properties in human umbilical vein endothelial cells (HUVEC) and aortic smooth muscle cells (HASMC) by enhancing NADPH oxidase expression. PCS also up-regulates the mRNA levels and the protein secretion of monocyte chemotactic protein-1 (MCP-1) in HUVEC. In HASMC, PCS increased the mRNA levels of alkaline phosphatase (ALP), osteopontin (OPN), core-binding factor alpha 1, and ALP activity. The knockdown of Nox4, a subunit of NADPH oxidase, suppressed the cell toxicity induced by PCS. The vascular damage induced by PCS was largely suppressed in the presence of probenecid, an inhibitor of organic anion transporters (OAT). In PCS-overloaded 5/6-nephrectomized rats, plasma MCP-1 levels, OPN expression, and ALP activity of the aortic arch were increased, accompanied by the induction of Nox4 expression. Collectively, the vascular toxicity of PCS can be attributed to its intracellular accumulation via OAT, which results in an enhanced NADPH oxidase expression and increased ROS production. In conclusion, we found for the first time that PCS could play an important role in the development of cardiovascular disease by inducing vascular toxicity in the CKD condition.

Cys34-cysteinylated human serum albumin is a sensitive plasma marker in oxidative stress-related chronic diseases.

The degree of oxidized cysteine (Cys) 34 in human serum albumin (HSA), as determined by high performance liquid chromatography (HPLC), is correlated with oxidative stress related pathological conditions. In order to further characterize the oxidation of Cys34-HSA at the molecular level and to develop a suitable analytical method for a rapid and sensitive clinical laboratory analysis, the use of electrospray ionization time-of-flight mass spectrometer (ESI-TOFMS) was evaluated. A marked increase in the cysteinylation of Cys34 occurs in chronic liver and kidney diseases and diabetes mellitus. A significant positive correlation was observed between the Cys-Cys34-HSA fraction of plasma samples obtained from 229 patients, as determined by ESI-TOFMS, and the degree of oxidized Cys34-HSA determined by HPLC. The Cys-Cys34-HSA fraction was significantly increased with the progression of liver cirrhosis, and was reduced by branched chain amino acids (BCAA) treatment. The changes in the Cys-Cys34-HSA fraction were significantly correlated with the alternations of the plasma levels of advanced oxidized protein products, an oxidative stress marker for proteins. The binding ability of endogenous substances (bilirubin and tryptophan) and drugs (warfarin and diazepam) to HSA purified from chronic liver disease patients were significantly suppressed but significantly improved by BCAA supplementation. Interestingly, the changes in this physiological function of HSA in chronic liver disease were correlated with the Cys-Cys34-HSA fraction. In conclusion, ESI-TOFMS is a suitable high throughput method for the rapid and sensitive quantification of Cys-Cys34-HSA in a large number of samples for evaluating oxidative stress related chronic disease progression or in response to a treatment.

Parathyroidectomy markedly reduces oxidative stress in a patient with primary hyperparathyroidism.

Parathyroidectomy for hyperparathyroidism has been associated with a survival benefit, but the mechanisms remain unclear. We are reporting on an 88-year-old female patient who had high serum calcium and intact parathyroid hormone levels associated with an enlarged parathyroid gland. A parathyroidectomy was performed due to a diagnosis of primary hyperparathyroidism. After the surgery, there was a marked decrease in the oxidative stress markers, such as the ratios of oxidized to unoxidized albumin and advanced oxidation protein products. These results suggest that parathyroidectomy reduces oxidative stress in patients with primary hyperparathyroidism, which may in part explain the reduced risk for cardiovascular and all-cause mortality after parathyroidectomy.