Vitamin C Deficiency Causes Cell Type-Specific Epigenetic Reprogramming and Acute Tubular Necrosis in a Mouse Model

Background: Vitamin C deficiency is found in patients with variable renal diseases. However, the role of vitamin C as an epigenetic regulator in renal homeostasis and pathogenesis remains largely unknown. Methods: We showed that vitamin C deficiency leads to acute tubular necrosis (ATN) using a vitamin C-deficient mouse model (Gulo knock-out). DNA/RNA epigenetic modifications and injured S3 proximal tubule cells were identified in the vitamin C-deficient kidneys using whole-genome bisulfite sequencing, methylated RNA immunoprecipitation sequencing, and single-cell RNA sequencing. Results: Integrated evidence suggested that epigenetic modifications affected the proximal tubule cells and fenestrated endothelial cells, leading to tubule injury and hypoxia through transcriptional regulation. Strikingly, loss of DNA hydroxymethylation and DNA hypermethylation in vitamin C-deficient kidneys preceded the histological sign of tubule necrosis, indicating the causality of vitamin C-induced epigenetic modification in ATN. Consistently, prophylactic supplementation of an oxidation-resistant vitamin C derivative, ascorbyl phosphate magnesium, promoted DNA demethylation and prevented the progression of cisplatin-induced ATN. Conclusions: Vitamin C played a critical role in renal homeostasis and pathogenesis in a mouse model, suggesting vitamin supplementation may be an approach to lower risk of kidney injury.

Edible Bird Nest Protects the Kidney From Gentamicin Induced Acute Tubular Necrosis

Every year, there are about 13.3 million cases of acute kidney injury (AKI). Although AKI is a preventable and treatable disease, if left untreated, it has high risk of multiple organ failure and progression to end stage kidney disease. Acute tubular necrosis (ATN) has been recognised as one of the major causes of AKI. Till to date, there is no effective supplement or medication in treating or reversing AKI. Most of the treatment strategies involve preventative measure to minimise the occurrence of AKI or to reverse the cause of AKI. Hence one of the primary area of research interests is to explore the potential treatment for AKI. Edible bird nests (EBN) are edible food produce by the swiftlet’s saliva, which is rich in sialic acids. Sialic acids are monosaccharides that play a vital role in maintaining the integrity and proper function of the human organs, including kidneys. EBN also contains epidermal growth factor, which is widely believed to have rejuvenation and tissue repairing properties. We initiate this study to study the potential reno-protective effect of edible bird’s nests by studying the Wistar rat model of gentamicin-induced AKI. Besides renal profiles, renal histology was also semiquantitatively assessed. In our study, pre-treatment with EBN prevented and ameliorated the gentamicin-induced AKI. To a lesser extent, post-treatment with EBN also protected the kidney from the toxic effect of gentamicin. Our findings are highly indicative that EBN possesses reno-protective properties.

Automobile Paint Reducer Induced Acute Kidney Injury

The various aspects of the automobile industry also carry with it the risk for occupational health hazards with it. Toluene has also evolved as a commonly used drug by substance abusers. Accidental exposure or self-poisoning with these substances has been reported in literature. These substances can also cause distal renal tubular acidosis (RTA), acute tubular necrosis, glomerulonephritis and interstitial nephritis, rhabdomyolysis and myoglobinemia.In this series, we report about three patients who developed renal manifestations because of organic solvents. Two of the three patients had ingested the paint reducer substance and the third one was addicted to sniffing the toluene based paint reducer. All the patients had in taken these substances with suicidal intent and developed acute kidney injury (AKI) and severe metabolic acidosis. One of the patients had features of rhabdomyolysis as well. The third patient was a substance abuser and had inhaled higher than usual dose and developed severe and refractory acidosis and mild kidney injury and required Renal Replacement Therapy (RRT) for acidosis. All the patients eventually recovered their kidney functions and were doing well during their follow-up.Toluene based organic solvents lead to acute neurological symptoms, accompanied by severe metabolic alterations, organ injury and dysfunc-tion. An association of the development of hypokalemic paralysis and metabolic acidosis with toluene intoxication has been observed. The management of acute toluene toxicity is mainly conservative, consisting of electrolytes correction, acid-base and fluid abnormalities and renal replacement therapy in severe AKI.Organic solvent exposure may result in acute tubular necrosis, rhabdomyolysis, RTA and AKI irrespective of the intake route. Clinical suspicion of organ dysfunction and failure and timely induction of supportive care leads to a good outcome.

D-Serine: A Cross Species Review of Safety

Background:D-Serine, a direct, full agonist at the D-serine/glycine modulatory site of the N-methyl-D-aspartate-type glutamate receptors (NMDAR), has been assessed as a treatment for multiple psychiatric and neurological conditions. Based on studies in rats, concerns of nephrotoxicity have limited D-serine research in humans, particularly using high doses. A review of D-serine's safety is timely and pertinent, as D-serine remains under active study for schizophrenia, both directly (R61 MH116093) and indirectly through D-amino acid oxidase (DAAO) inhibitors. The principal focus is on nephrotoxicity, but safety in other physiologic and pathophysiologic systems are also reviewed.Methods: Using the search terms “D-serine,” “D-serine and schizophrenia,” “D-serine and safety,” “D-serine and nephrotoxicity” in PubMed, we conducted a systematic review on D-serine safety. D-serine physiology, dose-response and efficacy in clinical studies and dAAO inhibitor safety is also discussed.Results: When D-serine doses >500 mg/kg are used in rats, nephrotoxicity, manifesting as an acute tubular necrosis syndrome, seen within hours of administration is highly common, if not universal. In other species, however, D-serine induced nephrotoxicity has not been reported, even in other rodent species such as mice and rabbits. Even in rats, D--serine related toxicity is dose dependent and reversible; and does not appear to be present in rats at doses producing an acute Cmax of <2,000 nmol/mL. For comparison, the Cmax of D-serine 120 mg/kg, the highest dose tested in humans, is ~500 nmol/mL in acute dosing. Across all published human studies, only one subject has been reported to have abnormal renal values related to D-serine treatment. This abnormality did not clearly map on to the acute tubular necrosis syndrome seen in rats, and fully resolved within a few days of stopping treatment. DAAO inhibitors may be nephroprotective. D-Serine may have a physiologic role in metabolic, extra-pyramidal, cardiac and other systems, but no other clinically significant safety concerns are revealed in the literature.Conclusions: Even before considering human to rat differences in renal physiology, using current FDA guided monitoring paradigms, D-serine appears safe at currently studied maximal doses, with potential safety in combination with DAAO inhibitors.

Galectin-3 Possesses Anti-Necroptotic and Anti-Apoptotic Effects in Cisplatin-Induced Acute Tubular Necrosis

BACKGROUND/AIMS: Acute kidney injury (AKI) is a public health burden with increasing morbidity, mortality and health care cost. It is associated with increased risk for the development of chronic kidney disease and death. Acute tubular necrosis (ATN) is the most common cause of AKI. Apoptosis and tissue necrosis play an important role in ATN. Galectin 3 (GAL-3), a beta galactoside binding lectin, is known to have a role in inflammation, apoptosis and oxidative stress but its role in cisplatin induced acute tubular necrosis is not clearly elucidated. METHODS: Male C57B6-J and C57BL-6 -GAL-3 knock-out mice were used to induce ATN using cisplatin mouse model of acute tubular necrosis. GAL-3 expression, apoptotic, necrotic and necroptotic proteins in kidneys were measured using standard histologic, immunohistochemical, and enzyme-linked immunosorbent assay techniques. Data were presented as mean ± S.E. Statistically significant differences (p<0.05) was calculated between experimental groups and corresponding control groups by one-way analysis of variance. RESULTS: There was a significant increase in GAL-3 in kidneys of cisplatin treated GAL-3 wild mice when compared with its control mice. In addition, there were significant higher percentage of ATN, higher levels of plasma urea and creatinine, and higher levels of cathepsin B and cathepsin D, in kidneys of cisplatin-treated GAL-3 KO mice than cisplatin-treated GAL-3 wild mice. Likewise, there were significant higher levels of necroptosis proteins RIPK1, RIPK3, and MLKL in kidneys of cisplatin-treated GAL-3 KO mice than cisplatin-treated GAL-3 wild mice. Moreover, there were significant higher levels of kidney pro-apoptotic proteins; cleaved caspase-3, cleaved PARP, TRAIL and FAS in cisplatin treated GAL-3 KO mice when compared with cisplatin treated GAL-3 wild mice. CONCLUSION: GAL-3 can affect cell survival and death through its interaction with necroptotic, apoptotic and pro-survival proteins in renal tubules during cisplatin-induced acute tubular necrosis.

MO134COVID-19-ASSOCIATED KIDNEY INJURY IS CHARACTERIZED BY ACUTE TUBULAR NECROSIS AND CAPILLARY CONGESTION WITH EVIDENCE FOR SARS-COV-2 IN THE NEPHRON

Background and Aims Kidney damage has been reported in COVID-19 patients. Despite numerous reports about COVID-19-associated nephropathy, the factual presence of the SARS-CoV-2 in the renal parenchyma remains controversial. Method We consecutively performed 16 immediate (≤3h) post-mortem renal biopsies in patients diagnosed with COVID-19. Kidney samples from 5 patients who died from sepsis and were free from COVID-19 were used as controls. Samples were methodically evaluated by 3 pathologists. Virus detection in the renal parenchyma was performed in all samples by bulk RNA RT-PCR (E and N1/N2 genes), immunostaining (nCoV2019 N-Protein), fluorescent in situ hybridization (nCoV2019-S) and electron microscopy. Results The mean age of our COVID-19 cohort was 68.2±12.8 years, most of whom were males (68.7%). Proteinuria was observed in 53.3% of cases, while acute kidney injury occurred in 60% of cases. Acute tubular necrosis of variable severity was found in all cases, with no tubular or interstitial inflammation. There was no difference in acute tubular necrosis severity between the patients with COVID-19 versus control samples. Congestion in glomerular and peri-tubular capillaries was respectively observed in 56.3 and 87.5% of patients with COVID-19 compared to 20% of controls, with no evidence of thrombi. The nCoV2019 N-Protein was detected in proximal tubules and also at the basolateral pole of scattered cells of the distal tubules in 9/16 cases. In situ hybridization confirmed these findings. RT-PCR of kidney total RNA detected SARS-CoV-2 N gene in one case. Electron microscopy did not show typical viral inclusions. Conclusion Our immediate post-mortem kidney samples from patients with COVID-19 highlight a congestive pattern of acute kidney injury, with no significant glomerular or interstitial inflammation. Immunostaining and in situ hybridization suggest that SARS-CoV-2 is present in various segments of the nephron.

MO166AUTOPTIC KIDNEY FINDINGS IN HOSPITALIZED PATIENTS WITH COVID-19

Background and Aims SARS-CoV-2, isolated for the first time at the end of 2019, is the third human infecting Coronavirus found so far. Acute kidney injury (AKI) is the most common presentation when kidney is involved. There is evidence that kidney damage is determined through different pathological mechanisms. Has been observed that pathological kidney lesions can be due to the direct cytopathic effect of the virus on tubular cells or by pro-inflammatory cytokine storm. Aim of this observation is to evaluate the clinical and pathological patterns of kidney damage mediated by Coronavirus. Method We analysed kidney autopsies of 4 patients with COVID-19 infection, hospitalized between March and April 2020, admitted to the Intensive Care Unit. The tissue samples have been observed by light microscopy and immunofluorescence. RT-PCR SARS-CoV-2 was performed in all cases. Results Case 1 female, 69 y; affected by obesity, previous ictus; smoking habit. Admitted for COVID-related pneumonia. At onset creatinine 0.45 mg/dl. Progression of lung failure and exitus after 3 days. Autopsy: diffuse alveolar damage. Renal autopsy: acute tubular necrosis; mild glomerular ischemia, lymphocyte T CD4+ parenchyma infiltration. Case2 male, 66 y; affected by hypertension with cardiac involvement. Admitted for persistent fever. At onset creatinine 0.98 mg/dl. Nasopharingeal swab COVID-19 positive. Progression of lung failure and oligoanuric AKIn 3 (creatinine 4.5 mg/dl, urea 239 mg/dl), dialysis dependent. Exitus after one week for diffuse alveolar damage and sepsis. Renal autopsy: proximal and distal acute tubular moderate injury, mild diffuse glomerular ischemia, glomerular capillaritis, overlap chronic nephropathy. Case 3 male 45 y; affected by obesity and diabetes. Admitted for COVID-related pneumonia with acute lung failure requiring ECMO. After one week developed AKIn 3 dialysis dependent. Exitus for cardio-respiratory arrest. Renal autopsy: diffuse acute tubular necrosis, glomerular capillaritis, overlap chronic diabetic nephropathy. Case 4 male, 51 y; affected by CKD grade IV, hypertension, previous ictus; drug abuser. Admitted for AKIn 2 and COVID-related pneumonia. After 3 days progression of lung and renal failure requiring intubation and dialysis treatment. Exitus the day after for diffusive alveolar damage and lymphocytic myocarditis. Renal autopsy: diffused acute tubular necrosis, glomerular ischemia with mild tuft collapsing, diffuse infiltration of lymphocytes CD4+. In all cases light microscopy examination showed diffuse proximal tubular injury, with isomeric and non-isomeric vacuolar degeneration; collapsing tuft, and interstitial inflammation. Virus RNA performed by RT-PCR on kidney tissue was positive in all patients. Moreover in some cases our patients showed multi-systemic organ involvement: lung in 4 cases, heart in 1, liver in 1. Conclusion Our observations show that the main pathological effect caused by Coronavirus is a direct cytopathic effect on the proximal tubules with variable degree of damage until acute tubular necrosis (ATN). In addition to this pathway, other factors contributing to kidney damage include systemic hypoxia, microvascular capillaritis. Associated sepsis can worse overall and renal survival. Previous comorbidities, especially obesity, diabetes, systemic hypertension and preexisting chronic renal failure, are significant negative prognostic factors.