Mechanisms and Models of Kidney Tubular Necrosis and Nephron Loss

Understanding nephron loss is a primary strategy for preventing chronic kidney disease (CKD) progression. Death of renal tubular cells may occur by apoptosis during developmental and regenerative processes. However, during acute kidney injury (AKI), the transition of AKI to CKD, sepsis-associated AKI, and kidney transplantation, ferroptosis and necroptosis, two pathways associated with the loss of plasma membrane integrity, kill renal cells. This necrotic type of cell death is associated with an inflammatory response, which is referred to as necroinflammation. Importantly, the necroinflammatory response to cells that die by necroptosis may be fundamentally different from the tissue response to ferroptosis. While mechanisms of ferroptosis and necroptosis have recently been investigated in detail, the cell death propagation during tubular necrosis, although described morphologically, remains incompletely understood. Here, we argue that a molecular switch downstream of tubular necrosis determines nephron regeneration vs. nephron loss, respectively. Unravelling the details of this "switch" must include the inflammatory response to tubular necrosis and regenerative signals potentially controlled by inflammatory cells, including the stimulation of myofibroblasts as the origin of fibrosis. Understanding in detail the molecular switch and the inflammatory responses to tubular necrosis can inform discussion of therapeutic options.

Histopathology and Renal Function in Wistar Rats after Intravascular Injection of Iodinated Contrast Media Iohexol and Iopamidol

This research aimed to analyze the histopathology (tubular necrosis and proteinaceous casts) and renal function (SCr and BUN) differences of male Wistar strain white rats (Rattus norvegicus) after intravascular injection of iodinated contrast media Iohexol and Iopamidol. This research is an experimental laboratory with a post-test only control group design. Male Wistar rats that fit the criteria were divided into three groups by random sampling technique: Control (K), Treatment 1 (P1, Iohexol 350 mg iodine/mL), and Treatment 2 (P2, Iopamidol 370 mg iodine/mL). Iohexol and Iopamidol were injected at a dose of 1600 mg iodine/kg BW. The histopathology differences were observed under a light microscope with a magnification of 400x, which were analyzed semi-quantitatively through slides formed by the paraffin method and H&E staining. SCr and BUN levels were checked using an automatic analysis machine with blood samples taken through the cardiac ventricle. Kruskal-Wallis test (α= 0.05) on renal histopathology scores, both tubular necrosis and protein casts showed Asymp. Sig. value > 0.05, which means there is no significant difference between the groups (K, P1, and P2). Kruskal-Wallis test (α= 0.05) on SCr levels also showed the Asymp. Sig. value > 0.05 and One-Way ANOVA Comparative Test on BUN levels showed the Sig. value > 0.05 which means there is no significant difference in renal function between the groups. This study proved no difference in histopathology and renal function in Wistar rats after injection of iodinated contrast media Iohexol and Iopamidol.

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.

Acute Liver Failure after Ingestion of Fried Rice Balls: A Case Series of Bacillus cereus Food Poisonings

Bacillus cereus foodborne intoxications and toxicoinfections are on a rise. Usually, symptoms are self-limiting but occasionally hospitalization is necessary. Severe intoxications with the emetic Bacillus cereus toxin cereulide, which is notably resistant heat and acid during cooking, can cause acute liver failure and encephalopathy. We here present a case series of food poisonings in five immunocompetent adults after ingestion of fried rice balls, which were massively contaminated with Bacillus cereus. The patients developed a broad clinical spectrum, ranging from emesis and diarrhoea to life-threatening acute liver failure and acute tubular necrosis of the kidney in the index patient. In the left-over rice ball, we detected 8 × 106Bacillus cereus colony-forming units/g foodstuff, and cereulide in a concentration of 37 μg/g foodstuff, which is one of the highest cereulide toxin contaminations reported so far from foodborne outbreaks. This report emphasizes the potential biological hazard of contaminated rice meals that are not freshly prepared. It exemplifies the necessity of a multidisciplinary approach in cases of Bacillus cereus associated food poisonings to rapidly establish the diagnosis, to closely monitor critically ill patients, and to provide supportive measures for acute liver failure and—whenever necessary—urgent liver transplantation.

Histomorphological assessment of non-neoplastic renal diseases at autopsy: an institutional experience in Southwestern Nigeria

BackgroundAutopsy remains an invaluable resource for medical education and establishing diagnosis of diseases that were missed prior to death. Many patients on admission in hospitals suffer kidney diseases that may contribute to their morbidity and/or mortality. The kidneys from autopsies provide opportunity to diagnose and understand some of these non-neoplastic renal lesions. This study aimed to present the frequency of non-neoplastic renal diseases at autopsy.Methods We conducted a five-year retrospective review of post-mortem records of deceased who had autopsy. Data such as age, sex, cause of death, and kidney lesions were extracted from the post-mortem records and clinical details were gotten from the clinical summaries in the autopsy reports. The kidneys were examined for pathological findings that were then classified into glomerular, tubulointerstitial (tubulointerstitial nephritis and other tubular lesions such as tubular necrosis, casts and fibrosis) and vascular lesions.Results A total of seventy (70) cases met the inclusion criteria with 91.4% having significant non- neoplastic renal lesions. The mean age of the deceased was 57.7years (18years – 91years). Males accounted for 65.7% of the cases. Glomerular lesions were seen in 84.3% of the cases, tubulointerstitial nephritis in 41.6% of cases, vascular lesions were seen in 30% of the cases and other tubular lesions (such as stones, casts and tubular necrosis) were seen in 52.9% of the cases. Cardiovascular diseases and infections were the major causes of death in these patients, accounting for 40% and 27% respectively. Renal diseases were attributed to immediate cause of death in 10% of the cases.Conclusion The kidney at autopsy provides a valuable renal pathology educational tool, as a wide range of medical renal lesions can be seen from kidneys examined at post mortem.

Farrerol Ameliorated Cisplatin-Induced Chronic Kidney Disease Through Mitophagy Induction via Nrf2/PINK1 Pathway

Previously, Our study has showed that farrerol can activate Nrf2 and ameliorate cisplatin-induced acute kidney injury (AKI). Mitophagy reportedly can prevent diabetic nephropathy, cisplatin-induced AKI and other related nephropathy. In this study, we evaluated the correlation between mitophagy and the protective effect of the Nrf2 activator farrerol on cisplatin-induced CKD by using C57BL/6 wild-type and Nrf2 knockout mice. We confirmed that Nrf2 and PINK1/Parkin-mediated mitophagy was significantly increased on the 3rd day of cisplatin stimulation but was reduced on the 38th day of cisplatin stimulation. Similar to previous results, farrerol activated Nrf2 on the 38th day of cisplatin administration, subsequently stimulating the Nrf2-targeted antioxidant enzymes HO-1 and NQO1. In addition, farrerol triggered PINK1/Parkin-mediated mitophagy by recruiting the receptor proteins LC3 and p62/SQSTM1, thereby eliminating damaged mitochondria. Furthermore, genetic deletion of Nrf2 reduced PINK1/Parkin-mediated mitophagy activation and led to increased renal tubular necrosis and renal fibrosis. We also found that farrerol alleviated inflammation and renal fibrosis by inhibiting p-NF-κB/NLRP3 and TGF-β/Smad signaling. These data indicated that farrerol effectively inhibited cisplatin-induced inflammation and renal fibrosis by activating Nrf2 and PINK1/Parkin-mediated mitophagy, which provides a potential novel therapeutic target for CKD.

Effect of flaxseed on systemic inflammation and oxidative stress in diabetic rats with or without chronic kidney disease

Background Diabetes mellitus (DM) and chronic kidney disease (CKD) are common causes of morbidity and mortality. Flaxseed contains several bioactive compounds that have been shown to possess anti-inflammatory and antioxidative properties. The aim of the present study was to investigate the possible effect of flaxseed in diabetic rats with adenine–induced CKD. Methods Male Wister rats (n = 48) were randomly divided into seven equal groups and treated for 33 consecutive days as follows: G1: control. G2 adenine, G3: streptozotocin (STZ), G4: flaxseed, G5: adenine+flaxseed, G6: STZ+flaxseed, G7: adenine+STZ+flaxseed). DM or CKD were experimentally induced by a single intraperitoneal injection of streptozotocin (STZ) or by adenine via oral gavage, respectively. Results Rats fed adenine alone exhibited several changes including decreased body weight, increased food and water intake and urine output, increased urinary albumin/creatinine ratio. They also showed an increase in plasma urea and, creatinine, indoxyl sulfate, neutrophil gelatinase-associated lipocalin and cystatin C, and a decrease in renalase activity. These were associated with significant changes in inflammatory and oxidative biomarkers, e.g., increase in 8-isoprostane, 8 -hydroxy -2-deoxy guanosine and decrease in antioxidant enzymes, as well as increase in interleukins 1β and 6, and NF-κB, and a decrease in interlukin-10. Histopathologically, there was increased tubular necrosis and fibrosis. Concomitant administration of adenine and STZ further worsened the renal damage induced by adenine alone. Flaxseed significantly ameliorated the changes caused by adenine and STZ, given either singly or in combination. Conclusion These findings suggest that flaxseed is a potential therapeutic agent in attenuating the progression of CKD in diabetes.

Acute kidney injury associated with COVID-19 infection: a case report

SARS-Cov2 infection is a highly transmissible disease associated with serious pulmonary disease. Renal involvement is frequent and associated with poor prognosis; however, mechanisms of kidney injury are not well established. We present a SARS-Cov2 patient with severe acute kidney injury. Kidney biopsy findings revealed a pattern of acute tubular necrosis with isometric vacuolization of the proximal tubule. The interstitium and glomeruli were normal. Electronic microscopy showed multiple viral-like particles in both the glomeruli and proximal tubule. This case study shows how SARS-Cov 2 infection can result in different kinds of kidney lesion.

Acute kidney injury and COVID-19

Background Coronavirus disease 2019 (COVID-19) is a recent pandemic infectious disease caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2). COVID-19 may lead to acute kidney injury (AKI). Main text SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) and dipeptidyl peptidase 4(DPP4) as entry point receptors in the alveolar type II cell of the lung. However, the expression of ACE2 is 100-fold higher in kidney tissue than the lung, though the potential entry point of SARS-CoV-2 for renal tissue and induction of AKI remains undefined. Therefore, reduction of ACE2 and high circulating angiotensin II in COVID-19 may together participate in the induction of AKI. Thereby, direct ACE2 activator is under investigation to be used as an effective therapy in the management COVID-19-induced AKI. Besides, the direct effect via invasion of SARS-CoV-2 may lead to glomerulopathy and renal proximal tubular necrosis. Conclusion COVID-19 may associate with AKI due to direct effect of SARS-CoV-2 through ACE2 and DPP4 receptors or indirectly through the development of cytokine storm. Both ACE2 and DPP4 are interacted mutually in the pathogenesis of AKI. Thus, DPP4 inhibitors or ACE2 activators could reverse early AKI in COVID-19. Therefore, emerging of clinical trials is warranted to confirm the role of ACE2 and DPP4 modulators in COVID-19-induced AKI.