Renoprotective effects of extracellular fibroblast specific protein 1 via nuclear factor erythroid 2-related factor-mediated antioxidant activity.

Podocyte expression of fibroblast specific protein 1 (FSP1) is observed in various types of human glomerulonephritis. Considering that FSP1 is secreted extracellularly and has been shown to have multiple biological effects on distant cells, we postulated that secreted FSP1 from podocytes might impact renal tubules. Our RNA microarray analysis in a tubular epithelial cell line (mProx) revealed that FSP1 induced the expression of heme oxygenase 1, sequestosome 1, solute carrier family 7, member 11, and cystathionine gamma-lyase, all of which are associated with nuclear factor erythroid 2-related factor (Nrf2) activation. Therefore, FSP1 is likely to exert cytoprotective effects through Nrf2-induced antioxidant activity. Moreover, in mProx, FSP1 facilitated Nrf2 translocation to the nucleus, increased levels of reduced glutathione, inhibited the production of reactive oxygen species (ROS), and reduced cisplatin-induced cell death. FSP1 also ameliorated acute tubular injury in mice with cisplatin nephrotoxicity, which is a representative model of ROS-mediated tissue injury. Similarly, in transgenic mice that express FSP1 specifically in podocytes, tubular injury associated with cisplatin nephrotoxicity was also mitigated. Extracellular FSP1 secreted from podocytes acts on downstream tubular cells, exerting renoprotective effects through Nrf2-mediated antioxidant activity. Consequently, podocytes and tubular epithelial cells have a remote communication network to limit injury.

Fanconi syndrome in an elderly patient with membranous nephropathy during treatment with the immunosuppressant mizoribine.

We report on an 80-year-old man diagnosed with Fanconi syndrome induced by mizoribine after 4 weeks of administration to treat membranous nephropathy. Mizoribine is an oral immunosuppressant that inhibits inosine monophosphate dehydrogenase and is widely used in Japan for the treatment of autoimmune diseases and nephrotic syndrome, as well as after renal transplantation. Acquired Fanconi syndrome is often caused by drugs (antibacterial, antiviral, anticancer, and anticonvulsant drugs) and is sometimes caused by autoimmune diseases, monoclonal light chain-associated diseases, or heavy metal poisoning. In our patient, hypokalemia, hypophosphatemia, glucosuria, hypouricemia, and severe proteinuria resolved gradually after discontinuation of mizoribine administration, despite oral administration of prednisolone followed by a single intravenous injection of rituximab. The patient was ultimately diagnosed with Fanconi syndrome induced by mizoribine based on his clinical course and his typical laboratory data with the absence of proximal tubular acidosis. To our knowledge, this is the first report of Fanconi syndrome possibly induced by mizoribine. Although the precise mechanism by which mizoribine induces proximal tubular dysfunction is unknown, we suggest that nephrologists should be aware of the onset of Fanconi syndrome, a rare complication during mizoribine treatment.

PPAR-δ activation reduces cisplatin-induced apoptosis via inhibiting p53/Bax/caspase-3 pathway without modulating autophagy in murine renal proximal tubular cells.

BACKGROUND: Cisplatin-induced injury of renal proximal tubular cells results basically from increased apoptosis via mitochondrial damage, and is mitigated by appropriate enhancement of autophagy. Peroxisome proliferator-activated receptor-delta (PPAR-δ) reportedly protects against not only mitochondrial damages but also enhances autophagy. Thus, PPAR-δ may protect against cisplatin-induced kidney injury. METHODS: We examined the protective effects of PPAR-δ activation on cisplatin-induced cellular injury and their detailed mechanisms in a murine renal proximal tubular (mProx) cell line using GW0742, an authentic PPAR-δ activator. Cisplatin-induced cell damages were evaluated by TUNEL assay and immunoblot analyses for p53, 14-3-3, Bax, Bcl2, cytochrome C, and activated caspases. Autophagy status was examined by immunoblot analyses for p62 and LC3. RESULTS: GW0742 suppressed cisplatin-induced apoptosis of mProx cells by reducing the activation of caspase-3 via attenuating the phosphorylation of p53 and 14-3-3, mitochondrial Bax accumulation, cytochrome C release from mitochondria to the cytosol and ensuing cytosolic caspase-9 activation. In contrast, GW0742 did not diminish cisplatin-enhanced activation of caspases-8 or -12 as extrinsic or endothelium reticulum apoptotic pathways, respectively. The inhibitory effect of GW0742 on cisplatin-induced caspase-3 activation was significantly diminished by silencing of the PPAR-δ gene expression. GW0742 itself had no influence on starvation-stimulated or cisplatin-induced autophagy in mProx cells, suggesting that the protective effects were not mediated by autophagy modification. CONCLUSION: Our results indicate that GW0742 may serve as a candidate agent to mitigate cisplatin nephrotoxicity via inhibiting the mitochondrial apoptotic pathway considerably depending on PPAR-δ, without modulating autophagy.

AR420626, a selective agonist of GPR41/FFA3, suppresses growth of hepatocellular carcinoma cells by inducing apoptosis via HDAC inhibition.

BACKGROUND: Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide and establishment of new chemotherapies for HCC is urgently needed. GPR41 [free fatty acid receptor 3 (FFA3)] is a G protein-coupled receptor for short chain fatty acids, including acetate, propionate, and butyrate. In our previous study, we showed that propionate enhances the cytotoxic effect of cisplatin in HCC cells and that this mechanism is dependent on inhibition of histone deacetylases (HDACs) via GPR41/FFA3. However, the antitumor action of GPR41/FFA3 has not been elucidated. METHODS: In this study, we examined AR420626 as a GPR41-selective agonist in HepG2 and HLE cells. Nude mice were used for HepG2 xenograft studies. The apoptotic effect of AR420626 was evaluated using flow cytometry analysis. Expression of apoptosis-related proteins and HDACs was evaluated by Western immunoblot. Gene silencing of HDAC 3/5/7 and GPR41 was performed using small interfering RNA. Expression of TNF-α mRNA was evaluated by TaqMan real-time polymerase chain reaction. RESULTS: We found that AR420626, a selective GPR41/FFA3 agonist, suppressed growth of HepG2 xenografts and inhibited proliferation of HCC cells by inducing apoptosis. AR420626 induced proteasome activation through mTOR phosphorylation, which reduced HDAC proteins, and then increased expression of TNF-α. CONCLUSION: AR420626, a selective GPR41/FFA3 agonist, may be a candidate as a therapeutic agent for HCC.

Preemptive HLA Antibody Screening Prior to Episodic Transplant Renal Biopsy Enables Early Diagnosis and Therapeutic Response in Asymptomatic Chronically Active Antibody-Related Rejection: A Case Report.

Common management of renal transplant recipients includes episodic renal biopsy based on clinical findings such as an increase in proteinuria or serum creatinine. When antibody-related rejection is suspected from the renal biopsy, subsequent testing for donor-specific antibodies (DSAs) is performed. We instead performed preemptive screening of asymptomatic post-renal transplant recipients for DSAs prior to renal biopsy. In this case, a 30-year-old woman with a secondary transplant was positive for 61 anti-HLA antibodies of class I and class II, among which DQ2 was a DSA with a mean fluorescence index of 2039. The patient had a living kidney transplant 9 years earlier. She had never been diagnosed with rejection, her serum creatinine was around 1.0 mg/dL, and her proteinuria was negative. Following the positive DSA result, a renal biopsy was performed, and she was diagnosed as C4d-negative chronic-active antibody-mediated rejection (CAABMR) with a Banff score of cg1b, (g + ptc) ≥ 2, and C4d 0. Intravenous steroid pulse, deoxyspagarin, antithymocyte globulin, rituximab, and oral everolimus were administrated. The treatment resulted in a gradual decrease in the DSA, which became negative 1 year later. The patient's serum creatinine remains around 1.0 mg/dL, and proteinuria remains negative. Treatments for advanced CAABMR are often expensive and ineffective. Our present case suggests that early detection and treatment through preemptive HLA antibody screening could improve the prognosis of renal transplants.

Chronic hypoxia exacerbates diabetic glomerulosclerosis through mesangiolysis and podocyte injury in db/db mice.

BACKGROUND: Chronic hypoxia may play a pivotal role in the development of diabetic nephropathy (DN). However, the precise mechanisms underlying progressive hypoxia-induced glomerular injury remain unclear. METHODS: We housed db/db mice in a hypoxia chamber (12% O2) for up to 16 weeks beginning at 8 weeks of age. Various urine, serum and kidney abnormalities and glomerular messenger RNA (mRNA) expression were compared with those in age-matched db/db mice housed under normoxia. RESULTS: Levels of urinary albumin and podocalyxin (PCX) were significantly higher in hypoxic mice early during hypoxia. Ultracentrifugation of urine samples revealed that podocytes in the hypoxic mice shed PCX-positive microparticles into the urine. After 16 weeks of hypoxia, the mice also had higher hematocrits with lower serum glucose and various degrees of mesangiolytic glomerulosclerosis with microaneurysms and the infrequent occurrence of nodular lesions. Immunohistologically, hypoxic mice showed significantly decreased endothelial cell densities early during hypoxia and decreased podocyte densities later. In both hypoxic and normoxic mice, glomerular macrophage and transforming growth factor-ß1 (TGF-ß1) staining significantly increased with aging, without changes in vascular endothelial growth factor or endothelial nitric oxide synthase (eNOS). Glomerular mRNA expression of monocyte chemoattractant protein-1, eNOS and TGF-ß1 was significantly enhanced in the hypoxic mice. CONCLUSIONS: These results indicate that chronic hypoxia induces advanced glomerulosclerosis with accelerated albuminuria triggered by mesangiolysis and podocyte injury in a murine model of DN.

Analytical and clinical validation of rapid chemiluminescence enzyme immunoassay for urinary thioredoxin, an oxidative stress-dependent early biomarker of acute kidney injury.

BACKGROUND: Oxidative stress is now recognized to be an important therapeutic target in kidney diseases. However, there are currently no biomarkers that can be used clinically to diagnose renal oxidative stress. METHODS: A rapid assay system for urinary thioredoxin 1, an oxidative stress-dependent biomarker of acute kidney injury (AKI), was developed as a chemiluminescence enzyme immunoassay and validated analytically and clinically. RESULTS: Analytic evaluation revealed that hemolytic hemoglobin caused measurements to be abnormally high, above the detectable range. However, urine sediment containing red blood cells did not affect the measurements. Assays using our proposed chemiluminescence enzyme immunoassay were completed within as little as 6 min, whereas a conventional ELISA > 4 h. Aciduria

Short-chain fatty acid mitigates adenine-induced chronic kidney disease via FFA2 and FFA3 pathways.

Short-chain fatty acids (SCFAs), including acetate, butyrate, and propionate, are produced when colonic bacteria in the human gastrointestinal tract ferment undigested fibers. Free fatty acid receptor 2 (FFA2) and FFA3 are G-protein-coupled receptors recently identified as SCFA receptors that may modulate inflammation. We previously showed through in vitro experiments that SCFAs activate FFA2 and FFA3, thereby mitigating inflammation in human renal cortical epithelial cells. This study used a murine model of adenine-induced renal failure to investigate whether or not SCFAs can prevent the progression of renal damage. We also examined whether or not these FFA2 and FFA3 proteins have some roles in this protective mechanism in vivo. Immunohistochemical analyses of mouse kidneys showed that FFA2 and FFA3 proteins were expressed mainly in the distal renal tubules and collecting tubules. First, we observed that the administration of propionate mitigated the renal dysfunction and pathological deterioration caused by adenine. Consistent with this, the expression of inflammatory cytokines and fibrosis-related genes was reduced. Furthermore, the mitigation of adenine-induced renal damage by the administration of propionate was significantly attenuated in FFA2-/- and FFA3-/- mice. Therefore, the administration of propionate significantly protects against adenine-induced renal failure, at least in part, via the FFA2 and FFA3 pathways. Our data suggest that FFA2 and FFA3 are potential new therapeutic targets for preventing or delaying the progression of chronic kidney disease.

ß-Hydroxybutyrate enhances the cytotoxic effect of cisplatin via the inhibition of HDAC/survivin axis in human hepatocellular carcinoma cells.

Ketone bodies, including acetoacetate and ß-hydroxybutyrate (ßOHB), are produced from acetyl coenzyme A in the liver and then secreted into the blood. These molecules are a source of energy for peripheral tissues during exercise or fasting. ßOHB has been reported to inhibit histone deacetylases (HDACs) 1, 3, and 4 in human embryonic kidney 293 cells. Thus, ßOHB may regulate epigenetics by modulating HDACs. There have been several reports that the administration of ßOHB or induction of a physiological state of ketosis has an antitumor effect; however, the mechanism remains unclear. The aim of this study was to investigate whether ßOHB enhances cisplatin-induced apoptosis in hepatocellular carcinoma (HCC) cells by modulating activity and/or expression of HDACs. We found that ßOHB significantly enhanced cisplatin-induced apoptosis and cleavage of caspase-3 and -8 in HCC cells. Further, ßOHB significantly decreased the expression of HDCA 3/5/6 and survivin in liver hepatocellular (HepG2) cells. In HDAC3/6 gene silencing, survivin expression was significantly decreased, and cisplatin-induced cleavage of caspase-3 was significantly enhanced compared with control in HepG2 cells. In conclusion, ßOHB enhanced cisplatin-induced apoptosis via HDAC3/6 inhibition/survivin axis in HepG2 cells, which suggests that ßOHB could be a new adjuvant agent for cisplatin chemotherapy.

ß-Hydroxybutyrate, a ketone body, reduces the cytotoxic effect of cisplatin via activation of HDAC5 in human renal cortical epithelial cells.

AIMS: ß-Hydroxybutyrate (ßOHB) is a metabolic intermediate that constitutes about 70% of ketone bodies produced in liver from oxidation of fatty acids released from adipose tissue. A recent study showed that ßOHB inhibits HDAC1, 3 and 4 (classes I and IIa) in human embryonic kidney 293 (HEK293) cells. Therefore, ßOHB could regulate epigenetics via modulating HDACs. However, little is known about the protective effect of ßOHB on renal cells through epigenetics. The aim of this study is to investigate whether ßOHB reduces cisplatin-induced nephrotoxicity in human renal cortical epithelial (HRCE) cells by modulating HDACs. MAIN METHODS: In this study, we used human renal cortical epithelial (HRCE) cells. The anti-apoptotic effect of ßOHB was evaluated using flow cytometry analysis. The expression of apoptosis-related proteins and HDACs was evaluated by western immunoblot. KEY FINDINGS: The results showed that ßOHB significantly reduced cisplatin-induced apoptosis in HRCE cells. Furthermore, ßOHB significantly reduced cisplatin-induced cleavage of caspase-3, acetylation of histone H3, and phosphorylation of AMP-activated kinase. This anti-apoptotic effect of ßOHB was markedly attenuated by an inhibitor of HDAC4/5, and ßOHB-mediated suppression of cleavage of caspase3 was significantly blocked by siRNA-induced gene silencing of HDAC5. SIGNIFICANCE: ßOHB attenuates cisplatin-induced apoptosis by activation of HDAC5 in HRCE cells, suggesting that ßOHB may be a new therapeutic agent for cisplatin nephropathy.

Elevated Levels of Urinary Extracellular Vesicle Fibroblast-Specific Protein 1 in Patients with Active Crescentic Glomerulonephritis.

BACKGROUND/AIMS: Extracellular vesicles (EVs), including exosomes, are present in various bodily fluids, including urine. We and others previously reported that cells expressing fibroblast-specific protein 1 (FSP1) accumulate within damaged glomeruli, and that urinary FSP1, as well as urinary soluble CD163, could potentially serve as a biomarker of ongoing glomerular injury. METHODS: To test that idea, we collected urine samples from 37 patients with glomerular disease; purified the urinary EVs; characterized them using Nanosight, western blotting, and immunoelectron microscopy; and determined FSP1 and soluble CD163 levels using enzyme-linked immunosorbent assays. RESULTS: Deemed to be mainly exosomes based on their size distribution, the EVs in urine contained FSP1, and a portion of the FSP1-positive vesicles was also positive for podocalyxin. FSP1 levels in urinary EVs were (1) positively correlated with rates of biopsy-proven cellular crescent formation (r = 0.562, p < 0.001) and total crescent formation (r = 0.448, p = 0.005) among total glomeruli; (2) significantly higher in patients with cellular crescents affecting 20% or more of their glomeruli than in those with fewer affected glomeruli (p = 0.003); and (3) significantly decreased after glucocorticoid and immunosuppressant therapy (p < 0.05). A positive correlation between FSP1 levels in urinary EVs and urinary soluble CD163 levels was confirmed (r = 0.367, p < 0.05). CONCLUSION: These data suggest that a portion of urinary FSP1 is secreted as EVs originating from podocytes, and that FSP1 levels reflect active and ongoing glomerular injury and disease activity, such as cellular crescent formation.

Tubulointerstitial Nephritis with IgM-Positive Plasma Cells.

Infiltration by IgG-positive plasma cells is a common finding in tubulointerstitial nephritis. Indeed, it has been thought that CD138-positive mature plasma cells secrete mainly IgG, and the occurrence of tubulointerstitial nephritis with CD138-positive plasma cells secreting IgM has rarely been reported. Routine immunofluorescence of fresh frozen sections is considered the gold standard for detection of immune deposits. However, the immunoenzyme method with formalin-fixed, paraffin-embedded sections is superior for detecting IgM- or IgG-positive cells within the renal interstitium, thus histologic variants may often go undetected. We recently discovered a case of tubulointerstitial nephritis showing IgM-positive plasma cell accumulation within the interstitium. To further explore the morphologic and clinical features of such cases, we performed a nationwide search for patients with biopsy-proven tubulointerstitial nephritis and high serum IgM levels. We identified 13 patients with tubulointerstitial nephritis and IgM-positive plasma cell infiltration confirmed with the immunoenzyme method. The clinical findings for these patients included a high prevalence of distal renal tubular acidosis (100%), Fanconi syndrome (92%), and anti-mitochondrial antibodies (82%). The pathologic findings were interstitial nephritis with diffusely distributed CD3-positive T lymphocytes and colocalized IgM-positive plasma cells, as well as tubulitis with CD3-positive T lymphocytes in the proximal tubules and collecting ducts. Additionally, levels of H+-ATPase, H+, K+-ATPase, and the HCO3--Cl- anion exchanger were markedly decreased in the collecting ducts. We propose to designate this group of cases, which have a common histologic and clinical form, as IgM-positive plasma cell-tubulointerstitial nephritis.

Short-chain fatty acids, GPR41 and GPR43 ligands, inhibit TNF-α-induced MCP-1 expression by modulating p38 and JNK signaling pathways in human renal cortical epithelial cells.

Short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, are produced predominantly by gut microbiota fermentation of dietary fiber. SCFAs are newly identified as endogenous ligands of two orphan G protein-coupled receptors, GPR41 and GPR43, which have the potential to modulate inflammation. Therefore, GPR41 and GPR43 may mediate the link between the gut microbiome status and various disease conditions including renal inflammation. This study aimed at investigating whether SCFAs activate GPR41 and GPR43, and thereby exert anti-inflammatory effects in human renal cortical epithelial cells (HRCEs) as a main component of kidney tissue. Immunohistochemical analyses of human renal biopsy specimens revealed the expression of GPR41 and GPR43 protein in the distal renal tubules and collecting tubules. TNF-α increased the expression of monocyte chemoattractant protein-1 (MCP-1), a potential fibrotic inducer, at least partly via enhancing phosphorylation of p38 and JNK in HRCEs. SCFAs, especially propionate, attenuated TNF-α- stimulated MCP-1 expression by inhibiting the phosphorylation of p38 and JNK. This inhibitory effect was considerably attenuated by an inactivator of the Gi/o-type G protein and a Gßγ (i/o) blocker, but not by a Gα (i/o) blocker. Furthermore, SCFA-mediated inhibition of MCP-1 expression was significantly blocked by siRNA-induced gene silencing of GPR41 and GPR43. In conclusion, SCFAs lowered TNF-α-induced MCP-1 expression by reducing phosphorylation of p38 and JNK in a GPR41/43-dependent manner in HRCEs, suggesting that SCFA modification may be a new therapeutic tool for preventing progression of renal inflammation and fibrosis.

A heterozygous female with Fabry disease due to a novel α-galactosidase A mutation exhibits a unique synaptopodin distribution in vacuolated podocytes.

We report the case of a 42-yearold woman diagnosed with heterozygous Fabry disease (FD) due to a novel α-galactosidase A Pro210Ser mutation and exhibiting a unique distribution of synaptopodin within podocytes. The patient was referred to our hospital with moderate proteinuria, and a renal biopsy was performed. Light microscopic examination of the specimen revealed diffuse global enlargement of podocytes, which also showed foamy changes. Electron microscopy revealed abundant myeloid bodies in podocytes and focal mitochondrial abnormalities within the tubules. The patient exhibited none of the characteristic symptoms of FD except hypohidrosis and had no obvious family history. Genetic analysis revealed a novel missense mutation (Pro210Ser) in the α-galactosidase A gene. She was ultimately diagnosed with FD based on immunohistochemical staining indicating large amounts of accumulated globotriaosylceramide in her podocytes, detection of urinary globotriaosylceramide secretion using high-performance thin-layer chromatography/ immunostaining, and structural modeling of the mutated α-galactosidase A (Pro210Ser). Immunostaining of the swollen and foamy podocytes using podocyte-associated antibodies (against podocalyxin, Wilms tumor-1, vimentin, and synaptopodin) revealed a unique distribution of synaptopodin surrounding globotriaosylceramide. To our knowledge, this is the first report of immunohistologically detected synaptopodin upregulation in foamy podocytes in a patient with FD.

Severe intraglomerular detachment of podocytes in a Gitelman syndrome patient.

We report the case of a 38-year-old woman diagnosed with Gitelman syndrome. A kidney biopsy showed abundant floating cells in the Bowman's space of the mildly cystic glomeruli, moderate tubulointerstitial changes and apparent intimal thickening of small arteries. These floating cells were immunohistologically identified as podocytes, by the expression of podocalyxin, vimentin, Wilms' tumor 1, synaptopodin and nephrin with positivities of 100%, 88.4%, 80.4%, 74.7% and 22.6%, respectively. In these phenotypes, nephrin expression was notably decreased in both detached and capillary-attached podocytes in comparison with normal control podocytes. Immunostaining of both detached and capillary-attached podocytes for Bax, Bcl-2, desmin, fibroblast-specific protein-1, α-smooth muscle actin and Ki-67 was negative, as were TUNEL assays. These results suggest that apoptosis and epithelial-mesenchymal transition were not the main cause of podocyte detachment in this patient. In addition, levels of urinary podocalyxin were not elevated, suggesting the detached podocytes were not excreted in the urine. To the best of our knowledge, this is the first report of severe intraglomerular non-apoptotic detachment of podocytes in Gitelman syndrome. This podocyte detachment may be associated with nephron obstruction and reduced nephrin expression.