Neutrophil depletion attenuates acute renal injury after exhaustive exercise in mice.

Prolonged intense exercise induces acute renal injury; however, the precise mechanism remains unclear. We investigated the effects of neutrophil depletion in male C57BL/6J mice. Male C57BL/6J mice were divided into four groups: sedentary with control antibody; sedentary with antineutrophil antibody; exhaustive exercise with control antibody; and exhaustive exercise with antineutrophil antibody. Antineutrophil (1A8) or control antibody was administered i.p. to the mice before they ran on a treadmill. Plasma levels of creatinine and blood urea nitrogen (BUN) were measured. Renal histology was assessed 24 h after exhaustive exercise, and the concentration of kidney injury molecule (KIM)-1 was measured using an enzyme-linked immunosorbent assay. The expression levels of inflammatory cytokines were measured using qRT-PCR. Furthermore, NADPH oxidase activity and the hydrogen peroxide concentration in the kidney were measured. Immediately after exhaustive exercise, plasma BUN was significantly increased, but creatinine was not. The increase in BUN after exercise was suppressed by 1A8 treatment. The pathological changes manifested as congested and swollen glomeruli and nuclear infiltration after exhaustive exercise. These changes were suppressed by treatment with the 1A8 antibodies. The KIM-1 concentration increased after exhaustive exercise but was reduced by the 1A8 antibodies. Treatment with the 1A8 antibody also decreased exhaustive exercise-induced inflammation and reactive oxygen species levels in the kidney. These results suggest that neutrophils contribute to exercise-induced acute renal injury by regulating inflammation and oxidative stress.

Quantification of the Plasma Concentration of Vadadustat by High-Performance Liquid Chromatography with Ultraviolet Detection and Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry.

BACKGROUND: An inexpensive, simple, and accurate plasma concentration measurement system is needed to actively conduct pharmacokinetic and pharmacodynamic analyses of vadadustat, hypoxia-inducible factor-prolyl hydroxylase inhibitor, in clinical settings. In this study, the authors aimed to develop a method for measuring vadadustat in human plasma that could be applied for therapeutic drug monitoring using high-performance liquid chromatography with ultraviolet detection (HPLC-UV) in a clinical setting. METHODS: Plasma samples (100 µL) were pretreated with acetonitrile using butyl paraoxybenzoate as an internal standard. Chromatographic separation was performed on a SunShell PFP C18 column (2.6 µm, 4.6 mm × 150 mm). The mobile phase consisted of (A) 20 mM of phosphate buffer (pH 2.4) and (B) acetonitrile (60:40, v/v), delivered isocratically at a flow rate of 1 mL/min. The analytes were detected by UV absorbance at a wavelength of 220 nm, and the column temperature was 40°C. To evaluate the applicability of HPLC-UV in a clinical setting, blood samples were collected at 19 time points from 7 patients who had been taking vadadustat. RESULTS: The calibration curve was linear over the concentration range of 0.2-150 mcg/mL (R2 > 0.99). Intra-assay and interassay accuracy, precision, and stability met the Food and Drug Administration recommendations. The vadadustat plasma concentrations of patients analyzed using the current HPLC-UV method were almost equal to those measured using ultra-performance liquid chromatography-tandem mass spectrometry (mean difference: 0.13 mcg/mL). Large variability in the dose-adjusted plasma concentrations of vadadustat at 12 hours after administration was observed between patients (coefficient of variation = 57.6%). CONCLUSIONS: This HPLC-UV method is a simple, accurate quantification method for evaluating plasma concentrations in patients taking vadadustat in a clinical setting.

Macrophage Depletion Attenuates Acute Renal Damage after Exhaustive Exercise in Mice.

Exhaustive exercise is known to induce acute renal damage. However, the precise mechanisms remain unclear. We investigated the effects of macrophage depletion on exhaustive exercise-induced acute renal damage. Male C57BL/6 J mice were divided into four groups: sedentary with control liposome (n=8), sedentary with clodronate liposome (n=8), exhaustive exercise with control liposome (n=8), and exhaustive exercise with clodronate liposome (n=8). Mice were treated with clodronate liposomes or control liposomes intraperitoneally for 48 h before undergoing exhaustive exercise. Renal function and renal histology were tested at 24 h. The expression levels of kidney injury molecule (KIM)-1 and inflammatory cytokines in kidney tissues were measured by quantitative RT-PCR, and KIM-1 concentration was semi-quantified by immunostaining. As a result, exhaustive exercise increased macrophage infiltration into the kidney. However, clodronate reduced it. Although exhaustive exercise resulted in an increase in KIM-1 mRNA expression levels and concentration, injection of clodronate liposome reduced it. In addition, TUNEL positive apoptotic cells were increased after exercise, but significantly reduced by clodronate. Clodronate liposome treatment also decreased the mRNA expression levels of inflammatory cytokines (TNF-α, IL-1ß, and IL-6) in the kidney after exhaustive exercise. These results suggest that macrophages play a critical role in increasing renal damage by regulating inflammation.

Survey on attitudes toward brain-dead and living donor transplantation in medical students: a cross-sectional study in Japan.

BACKGROUND: Although a shortage in organ donation is a critical problem in Japan, understanding of and attitude toward organ transplantation in medical students have not been sufficiently reported. METHODS: Between 2013 and 2018, we surveyed 702 medical students in the fifth-year clinical training in our urology department. The survey concerned (1) knowledge of Japanese transplantation law, which was amended in 2010, and (2) whether the respondents had an organ donor card and had agreed to be a brain-dead donor or a living donor in kidney transplantation with specific reasons for their choices. RESULTS: All 702 students answered the survey. Of 657 students who provided valid answers to the first section, 402 (61%) recognized the amendment to the Japanese transplantation law, and only 11 (1.7%) fully understood its contents. Of 702 students, 194 (28%) had a donor card, 384 (55%) agreed to be a brain-dead donor, and 529 (75%) agreed to be a living donor in kidney transplantation. As the specific reasons for their choices, only a few medical students wrote reasons based on their medical standpoint, and more students wrote emotional reasons. CONCLUSIONS: The understanding of and attitude toward organ transplantation were not remarkably high in the fifth-year medical students in Japan. To solve the donor shortage problem, education about organ transplantation may need to be more effective.

Impact of distance between donor and recipient hospitals on cadaveric kidney transplantation outcomes.

BACKGROUND: The impact of distance between donor and recipient hospitals on outcomes in cadaveric kidney transplantations is unknown. We investigated the association between inter-hospital distance and outcomes in cadaveric kidney transplantations in Japan. METHODS: We retrospectively analyzed 363 cadaveric kidney transplantations between 2002 and 2017 in Japan. Inter-hospital distance, graft transport time, total ischemic time (TIT), and graft survival were compared between our hospital and national transplantation cohort in Japan. Estimated glomerular filtration rate (eGFR) 1 month and 1 year after transplantation was compared between cadaveric and living-donor kidney transplantations in our hospitals. Additionally, inter-hospital distances among the seven geographical regions in Japan were assessed. RESULTS: There were 12 and 351 cadaveric kidney transplantations at our hospital and in Japan, respectively. Mean inter-hospital distance at our hospital (217 ± 121 km) was significantly longer than that of the national cohort (53 ± 80 km; P < 0.001). Mean TIT and graft survival for our hospital and national cohort were 539 ± 200 min and 91% and 491 ± 193 min and 81%, respectively. Mean eGFRs 1 year after cadaveric and living-donor transplantations at our hospitals were comparable (47 ± 16 vs. 47 ± 15 mL/min/1.73 m2). The comparison among seven regions in Japan indicated a regional difference in inter-hospital distance with an association between area (km2) and inter-hospital distance (km). CONCLUSIONS: Despite the longer inter-hospital distance at our hospital, TIT and transplant outcomes were acceptable in our cases. In addition, geographical inequity in graft allocation in Japan was suggested.

Daclatasvir/asunaprevir based direct-acting antiviral therapy ameliorate hepatitis C virus-associated cryoglobulinemic membranoproliferative glomerulonephritis: a case report.

BACKGROUND: Direct-acting antivirals (DAAs) dramatically improve the treatment of hepatitis C virus (HCV) infections. However, the effects of DAAs on extra-hepatic manifestations such as HCV-associated glomerulonephritis, especially in cases with renal dysfunction, are not well elucidated. CASE PRESENTATION: A 69-year-old Japanese woman was diagnosed as having chronic hepatitis C, genotype 1b at the age of 55. She presented with hypertension, microscopic hematuria, proteinuria, renal dysfunction, purpura, and arthralgia at the age of 61. She also had hypocomplementemia and cryoglobulinemia. Renal biopsy revealed membranoproliferative glomerulonephritis (MPGN), and she was diagnosed as having HCV-associated cryoglobulinemic MPGN. She declined interferon therapy at the time and was treated with antihypertensive medications as well as oral corticosteroid that were effective in reducing proteinuria. However, when the corticosteroid dose was reduced, proteinuria worsened. She began antiviral treatment with daclatasvir/asunaprevir (DCV/ASV). Clearance of HCV-RNA was obtained by 2 weeks and sustained, and liver function was normalized. In addition, microhematuria turned negative, proteinuria decreased, hypocomplementemia and estimated glomerular filtration rate were improved, whereas cryoglobulinemia persisted. She completed 24 weeks of therapy without significant adverse effects. CONCLUSION: In a case of HCV-associated cryoglobulinemic MPGN with renal dysfunction, DCV/ASV -based DAAs ameliorated microhematuria, proteinuria and renal function without significant side effects.

NF-κB-dependent increase in tissue factor expression is responsible for hypoxic podocyte injury.

BACKGROUND: Fibrin deposition within glomeruli is commonly seen in kidney biopsy specimens, suggesting enhanced coagulant activity. Tissue factor (TF) is a coagulation factor which is also related to various biological effects, and TF is upregulated by hypoxia in cancer cells. Recently, hypoxic podocyte injury has been proposed, therefore, we investigated TF expression in hypoxia. METHODS: Conditionally immortalized human podocytes were differentiated and treated under hypoxic or normoxic conditions. mRNA expressions of TF and tissue factor pathway inhibitor (TFPI) were analyzed by quantitative RT-PCR. Protein levels of TF and TFPI were tested by enzyme-linked immunosorbent assay. We employed small interfering RNA (siRNA) to temporary knockdown early growth response protein 1 (Egr-1), hypoxia-inducible factor-1α (HIF-1α) and TF. The expression of CD2-associated protein (CD2AP) mRNA and phalloidin staining was examined to assess podocyte injury. RESULTS: Hypoxia increased mRNA expression of TF (6 h: 2.3 ± 0.05 fold, p < 0.001, 24 h: 5.6 ± 2.4 fold, p < 0.05) and suppressed TFPI (6 h: 0.54 ± 0.04 fold, p < 0.05, 24 h: 0.24 ± 0.06 fold, p < 0.001) compared with normoxia. Similarly, protein levels of TF were increased and TFPI were decreased. Egr-1 siRNA did not change TF mRNA expression. Pyrrolidine dithiocarbamate (PDTC), a nuclear factor kappa B (NF-κB) inhibitor, significantly reduced hypoxia induced TF expression, and HIF-1α knockdown further increased TF. Hypoxia resulted in decreased CD2AP and actin reorganization in podocytes, and these changes were attenuated by TF siRNA. CONCLUSION: Hypoxia increased the expression of TF in human podocytes NF-κB dependently. TF may have a critical role in the hypoxic podocyte injury.

Effects of Serum Uric Acid on Estimated GFR in Cardiac Surgery Patients: A Pilot Study.

BACKGROUND: The aim of the study was to investigate the effects of serum uric acid (SUA) on acute kidney injury (AKI) in patients undergoing cardiac surgery. METHODS: Prospectively collected data from a previous study were analyzed to investigate the relationship between SUA and AKI as assessed by neutrophil gelatinase-associated lipocalin (NGAL), serum creatinine (SCr) and kinetic estimated glomerular filtration rate (KeGFR). RESULTS: Patients undergoing cardiovascular surgery (n = 37) were included. SUA was measured at postoperative 1 h. Statistically significant correlations were present between SUA and NGAL measured at postoperative 1 h (r = 0.39, p = 0.008), 6 h (r = 0.31, p = 0.029) and 24 h (r = 0.31, p < 0.001), respectively. Significant correlations were also noted between SUA and SCr measured on postoperative day 1 (r = 0.41, p = 0.006), day 2 (r = 0.29, p = 0.042) and day 3 (r = 0.42, p = 0.009). Negative correlations were demonstrated between SUA and day 1 (r = -0.44, p = 0.007), day 2 (r = -0.43, p = 0.007), day 3 (r = -0.44, p = 0.006 and day 4 KeGFR (r = -0.35, p = 0.035). The inverse relationship of SUA and KeGFR was also demonstrated with a different method (Jelliffe) of measurement. CONCLUSIONS: A reduction in glomerular filtration rate (GFR) can lead to a rise in SUA. However, in this study, we are able to show that SUA at 1 h (maximal dilution time) effectively predicts subsequent changes in urinary NGAL, SCr, KeGFR, and the development of AKI. Thus, these findings suggest that uric acid precedes and predicts acute changes in renal function and cannot be ascribed to a simple relationship in which a reduced GFR raises SUA.

Toll-like receptor 3 signaling contributes to the expression of a neutrophil chemoattractant, CXCL1 in human mesangial cells.

BACKGROUND: Mesangial proinflammatory chemokine/cytokine expressions via innate immunity play a pivotal role in the pathogenesis of glomerulonephritis. CXCL1/GROα is a strong neutrophil chemoattractant cytokine and reportedly plays an important role in regional inflammatory reactions. However, detailed signaling of mesangial CXCL1 expression induced by viral or "pseudoviral" immunity remains to be determined. METHODS: We treated normal human mesangial cells (MCs) in culture with polyinosinic-polycytidylic acid (poly IC), an authentic double-stranded RNA, and analyzed the expression of CXCL1 by reverse transcription-polymerase chain reaction (RT-PCR), real-time quantitative RT-PCR and enzyme-linked immunosorbent assay. To elucidate the poly IC-induced signaling pathway for CXCL1 expression, we subjected the cells to RNA interference against Toll-like receptor (TLR) 3, retinoic acid-inducible gene-I (RIG-I), melanoma differentiation-associated gene 5 (MDA5), interferon (IFN)-ß, nuclear factor (NF)-κB p65 and IFN regulatory factor (IRF) 3. We also conducted an immunofluorescence study to examine mesangial CXCL1 expression in biopsy specimens from patients with lupus nephritis (LN) and IgA nephropathy (IgAN). RESULTS: We found that activation of TLR3 signaling could induce the expression of CXCL1 in MCs. NF-κB, IRF3 and IFN-ß, but neither RIG-I nor MDA5, were found to be involved in mesangial CXCL1 expression in this setting. Induction of CXCL1 by poly IC was inhibited by pretreatment of cells with dexamethasone. Intense glomerular CXCL1 expression was observed in biopsy specimens from patients with LN, whereas only a trace staining occurred in specimens from patients with IgAN. CONCLUSION: TLR3 signaling also contributes to the CXCL1 expression in MCs. These observations further support the implication of viral and "pseudoviral" immunity in the pathogenesis of inflammatory renal diseases, especially in LN.

A case of membranoproliferative glomerulonephritis associated with curved fibril deposition.

BACKGROUND: It is sometimes challenging to diagnose unsusual cases of fibrillary glomerulonephritis (FGN) and immunotactoid glomerulopathy (ITG), the rare causes of nephrotic syndrome. CASE PRESENTATION: A 75-year-old Japanese woman presented with nephrotic syndrome, microhematuria and renal insufficiency. Renal biopsy revealed membranoproliferative glomerulonephritis (MPGN) with IgM and weak C3 deposition. Congo red stain was negative. Electron microscopy demonstrated massive fibrils in the subendothelium, mesangium and subepithelium. The fibrils were partially parallel, partially curved and 17 nm in diameter. Cryoglobulin, hepatitis B virus (HBV) antigen, hepatitis C virus (HCV) antibody or antinuclear antibody were negative. CONCLUSION: We report a case of MPGN associated with peculiar non-amyloid fibril deposition corresponding to neither FGN nor ITG.

Role of High-sensitivity C-reactive Protein in Future Cardiovascular Events in Hemodialysis Patients.

BACKGROUND/AIM: The pathogenesis of cardio-vascular disease (CVD) in hemodialysis (HD) patients involves inflammation and oxidative stress. High-sensitivity C-reactive protein (hs-CRP) is an established inflammatory biomarker associated with CVD. Several studies have suggested that the inflammatory biomarker pentraxin-3 (PTX-3) and the oxidative stress-related biomarker soluble lectin-like low-density lipoprotein receptor-1 (sLOX-1) are novel biomarkers for CVD in non-HD populations. This study aimed to clarify the association of these established and novel biomarkers with future cardiovascular (CV) events in HD patients. PATIENTS AND METHODS: This was a single-center prospective cohort study that included 255 HD patients. The primary outcome was the composite of nonfatal and fatal CV events. The event-free survival rate between the two groups according to the median plasma level of each biomarker at baseline was evaluated using the Kaplan-Meier method. The risk for CV events at elevated levels of each biomarker was estimated using Cox proportional hazard model. RESULTS: We observed 44 CV events during the median follow-up period of 743 days. The event-free survival rate significantly differed between the two groups in hs-CRP but not in PTX-3 or sLOX-1. The unadjusted hazard ratio (HR) for CV events in patients with hs-CRP levels above the median was 2.63 [95% confidence interval (CI)=1.37-5.02]. The HR remained significant after adjusting for age, sex, history of CVD, and diabetes (HR=2.30; 95%CI=1.20-4.43). CONCLUSION: In HD patients, hs-CRP may have a predictable role for future CV events, whereas PTX-3 and sLOX-1 do not.

Toll-like receptor 3 ligand, polyIC, induces proteinuria and glomerular CD80, and increases urinary CD80 in mice.

BACKGROUND: We have reported that children with biopsy-proven minimal change disease (MCD) express CD80 (also known as B7.1) in their podocytes and excrete high levels of CD80 in their urine during active nephrotic syndrome. We also reported that polyIC, a Toll-like receptor 3 ligand, increases CD80 mRNA and protein expression in cultured human podocytes dose-dependently, with actin re-organization and a reduction in synaptopodin expression. METHODS: To determine the effect of polyIC in the kidney, we subjected mice to systemic injection of polyIC or phosphate buffered saline. RESULTS: Mice injected with polyIC developed significant proteinuria with increased urinary CD80 excretion. Glomeruli from mice injected with polyIC were normal by light microscopic examination, but showed increased CD80 production in podocytes by immunofluorescence staining. In isolated glomeruli from mice injected with polyIC, expressions of CD80 and interleukin 10 significantly increased with a mild non-significant increase in CTLA-4, and synaptopodin expression decreased significantly. CONCLUSIONS: Our study demonstrates that systemically administered polyIC can induce transient proteinuria and urinary CD80 excretion with an increase in CD80 production in podocytes, increased glomerular CD80 and reduced synaptopodin expression. These findings may be relevant to the pathogenesis of proteinuria in MCD.

Serum from minimal change patients in relapse increases CD80 expression in cultured podocytes.

BACKGROUND: Minimal change disease (MCD) is the most common cause of nephrotic syndrome in children and is associated with the expression of CD80 in podocytes and the increased excretion of CD80 in urine. We hypothesized that serum from patients with MCD might stimulate CD80 expression in cultured podocytes. METHODS: Sera and peripheral blood mononuclear cells (PBMCs) were collected from subjects with MCD in relapse and remission and from normal controls. Immortalized human podocytes were incubated with culture media containing patient sera or supernatants from patient and control PBMC cultures. CD80 expression was measured by quantitative PCR and western blot analysis. RESULTS: Sera collected from patients with MCD in relapse, but not in remission, significantly increased CD80 expression (mean ± standard deviation: 1.8 ± 0.7 vs. 0.8 ± 0.2; p < 0.004) and CD80 protein secretion by podocytes (p < 0.05 between relapse and normal controls). No such CD80 increase was observed when podocytes were incubated with supernatants of PBMC cultures from patients in relapse. CONCLUSIONS: Sera from MCD patients in relapse, but not in remission, stimulated CD80 expression in cultured podocytes. Identifying this factor in sera could provide insights into the pathogenesis of this disorder. No role in CD80 expression by podocytes was found for cytokines released by PBMCs.

Minimal change disease in graft versus host disease: a podocyte response to the graft?

Nephrotic syndrome is a rare complication of hematopoietic cell transplantation. It has been suggested that nephrotic syndrome may represent a limited form of graft-versus-host disease although the pathological link between these two entities remains unclear. In this paper, we report a case of a 61-year-old female who underwent nonmyeloablative allogenic stem cell transplantation for T-cell prolymphocytic leukemia and subsequently developed biopsy proven minimal change disease shortly after cessation of her immunosuppression therapy. Urinary CD80 was markedly elevated during active disease and disappeared following corticosteroid-induced remission. We hypothesize that alloreactive donor T cells target the kidney and induce podocyte expression of CD80 that results in proteinuria from limited 'graft versus host' disease.

A case of myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-associated glomerulonephritis and concurrent membranous nephropathy.

BACKGROUND: Myeloperoxidase anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (MPO-ANCA-GN) and concurrent membranous nephropathy (MN) are very rare combination. Their causal relationship has been suggested, but not determined. CASE PRESENTATION: A 73-years-old male with 5-year history of proteinuria underwent an operation for his sigmoid colon cancer. Seven months later, he was referred to a nephrology division due to an exacerbating renal function and hypoalbuminemia. Laboratory examination revealed positive MPO-ANCA in the serum. A renal biopsy revealed a necrotizing extracapillary proliferative glomerulonephritis with crescents, demonstrating MPO-ANCA-GN. Whereas, immunofluorescent staining documented granular deposition of immumoglobulin (Ig) G and C3 along the capillary wall and electron microscopy showed subepithelial deposits in the glomerular basement membrane demonstrating MN. Immunofluorescent staining of IgG subclass showed positive IgG1, IgG2, negative IgG3 and weak positive IgG4 suggested the possibility of malignancy-associated MN. CONCLUSION: Combination of MPO-ANCA-GN and MN are rare. Although the causal relationship has been suggested in some cases, we should consider all the possibilities including idiopathic MN and secondary MN associated with malignancy, drug use or infection.

Quality of life in patients with minimal change nephrotic syndrome.

AIM: The goal of the study was to investigate quality of life (QOL) in adult patients with minimal change nephrotic syndrome (MCNS) and to test the relationship of QOL with the level of self-care. MATERIALS AND METHODS: We distributed two questionnaires to 30 outpatients with MCNS. The MOS 36-item Short Form Health Survey (SF-36v2) was used to examine health-related QOL in comparison with normative data from the general Japanese population and a population with two chronic diseases. SF-36v2 consists of 36 questions classified into 8 subscales. We also used the Self-Care Behavior Scale for patients with chronic kidney disease (CKD), which consists of 31 questions with 4 subscales. RESULTS: The SF-36v2 social functioning subscale was most impaired and bodily pain was least affected in patients with MCNS. The self-care subscales of information/communication and positive behavior had positive correlations with the QOL subscales of mental health (P<0.05) and vitality (P<0.05). The correlation between social functioning and information/communication was close to significant (P=0.051). CONCLUSION: In MCNS, social functioning was particularly impaired. Our results suggest that better self-care can have a positive impact on QOL in patients with MCNS.

Valacyclovir-associated acute kidney injury and encephalopathy in an elderly woman with normal kidney function: a case report.

A 72-year-old Japanese woman was treated by 3000 mg/day of valacyclovir for the herpes zoster in her left back. She had been treated as hypertension with no renal insufficiency. In two days, she visited an emergency room of a regional stroke care center with dysarthria, dexterity disorder and gait disturbance. Neither head CT nor MRI found intracranial lesions, then, laboratory tests revealed that her serum creatinine level was 4.63 mg/dL. She was transferred and admitted to our hospital on the following day and received hemodialysis under the diagnosis of AKI due to acyclovir accompanied with encephalopathy. Afterward, her serum concentration of acyclovir revealed as 44 µg/mL, which is extremely high. Her neurological symptom disappeared in parallel with the decrease of serum concentration of acyclovir. She received 3 sessions of hemodialysis and discharged on the 8th day of admission with almost normal renal function and no neurological sequela.

Hypoxia-inducible Factor-1α Suppresses the Innate Immune Response in Cultured Human Proximal Tubular Cells.

BACKGROUND/AIM: Retinoic acid-inducible gene (RIG)-I like receptors (RLRs) are expressed on renal proximal tubular epithelial cells (RPTECs) in viral nephropathy, indicating the presence of RLR-mediated innate immune responses in RPTECs. Hypoxia is also known to affect innate immunity. This study investigated the effects of hypoxia, and hypoxia-inducible factor (HIF) on innate immunity in RPTECs. MATERIALS AND METHODS: Primary human RPTECs were cultured under normoxic or hypoxic conditions and treated with a synthetic analog of double-stranded RNA (polyIC). The expression levels of RIG-I and MDA5, as RLRs, and IFNß, IL6, and TNFα, as inflammatory mediators were evaluated using quantitative reverse transcription-polymerase chain reaction, western blotting, and lactate dehydrogenase activity (LDH) assays. To further investigate the role of hypoxia, a small interfering RNA was used to knockdown HIF1α. RESULTS: Under normoxic conditions, polyIC increased RIG-I, MDA5, and IFNß mRNA expression in RPTECs by, 9.4±0.4-, 10.8±0.5-, and 4.0±0.1-fold, respectively, compared to control, and by 5.4±0.1-, 7.4±0.1-, and 2.4±0.3-fold, respectively, under hypoxic conditions, the rate of increase was lower than that under normoxic conditions (p<0.01). Protein expression showed a similar trend. Under hypoxic conditions, polyIC treatment with HIF1α knockdown in RPTECs increased RIG-I, MDA5, and IFNß mRNA expression by 3.1±0.5-, 2.9±0.4-, and 6.1±0.4-fold, respectively, and cytotoxicity, demonstrated by LDH assay, was increased compared to that without knockdown (all p<0.01). CONCLUSION: Hypoxia suppresses polyIC-induced RLRs mediated innate immune responses in RPTECs via HIF1α.