Perinatal asphyxia leads to acute kidney damage and increased renal susceptibility in adulthood.

Perinatal asphyxia (PA) poses a significant threat to multiple organs, particularly the kidneys. Diagnosing PA-associated kidney injury remains challenging, and treatment options are inadequate. Furthermore, there is a lack of long-term follow-up data regarding the renal implications of PA. In this study, 7-day-old male Wistar rats were exposed to PA using a gas mixture (4% O2; 20% CO2 in N2 for 15 min) to investigate molecular pathways linked to renal tubular damage, hypoxia, angiogenesis, heat shock response, inflammation, and fibrosis in the kidney. In a second experiment, adult rats with a history of PA were subjected to moderate renal ischemia-reperfusion (IR) injury to test the hypothesis that PA exacerbates renal susceptibility. Our results revealed an increased gene expression of renal injury markers (kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin), hypoxic and heat shock factors (hypoxia-inducible factor-1α, heat shock factor-1, and heat shock protein-27), proinflammatory cytokines (interleukin-1ß, interleukin-6, tumor necrosis factor-α, and monocyte chemoattractant protein-1), and fibrotic markers (transforming growth factor-ß, connective tissue growth factor, and fibronectin) promptly after PA. Moreover, a machine learning model was identified through random forest analysis, demonstrating an impressive classification accuracy (95.5%) for PA. Post-PA rats showed exacerbated functional decline and tubular injury and more intense hypoxic, heat shock, proinflammatory, and profibrotic response after renal IR injury compared with controls. In conclusion, PA leads to subclinical kidney injury, which may increase the susceptibility to subsequent renal damage later in life. In addition, the parameters identified through random forest analysis provide a robust foundation for future biomarker research in the context of PA.NEW & NOTEWORTHY This article demonstrates that perinatal asphyxia leads to subclinical kidney injury that permanently increases renal susceptibility to subsequent ischemic injury. We identified major molecular pathways involved in perinatal asphyxia-induced renal complications, highlighting potential targets of therapeutic approaches. In addition, random forest analysis revealed a model that classifies perinatal asphyxia with 95.5% accuracy that may provide a strong foundation for further biomarker research. These findings underscore the importance of multiorgan follow-up for perinatal asphyxia-affected patients.

The Sigma-1 Receptor Is a Novel Target for Improving Cold Preservation in Rodent Kidney Transplants.

Kidney transplantation is the preferred treatment for patients with end-stage kidney disease. Maintaining organ viability between donation and transplantation, as well as minimizing ischemic injury, are critically important for long-term graft function and survival. Moreover, the increasing shortage of transplantable organs is a considerable problem; thus, optimizing the condition of grafts is a pivotal task. Here, rodent models of kidney transplantation and cold storage were used to demonstrate that supplementation of a preservation solution with Sigma-1 receptor (S1R) agonist fluvoxamine (FLU) reduces cold and warm ischemic injury. Post-transplant kidney function was improved, histological injury was mitigated, and mRNA expression of two tubular injury markers-kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin-was robustly reduced. In addition, renal inflammation was diminished, as shown by reduced leukocyte infiltration and pro-inflammatory cytokine expression. In the cold ischemia model, FLU ameliorated structural injury profoundly after 2 h as well as 24 h. The reduced number of TUNEL-positive and Caspase 3-positive cells suggests the anti-apoptotic effect of FLU. None of these beneficial effects of FLU were observed in S1R-/- mice. Of note, organ damage in FLU-treated kidneys after 24 h of cold storage was similar to just 2 h without FLU. These results indicate that S1R agonists can prolong storage time and have great potential in improving organ preservation and in alleviating the problem of organ shortages.

Lyophilization and homogenization of biological samples improves reproducibility and reduces standard deviation in molecular biology techniques.

Lyophilization is a cost-effective method for biological specimen preservation but detailed tissue-specific reference protocols are still lacking. Moreover, data are limited on the long-term stability of proteins and nucleic acids in lyophilized samples.Here, we offer lyophilization protocols for various rat and mouse tissues (kidney, heart, liver, lung, aorta, and skin) coupled with technical hints for optimal sample preparation. We demonstrate that lyophilized samples stored at 4 °C for 20 months can yield protein and RNA of similar quantity and quality to -80 °C storage, while phosphorylated proteins are preserved as well. Freeze-dried and subsequently pulverized samples can provide more consistent, more reliable data especially when investigating focal injuries, such as fibrosis. We developed a protocol for the concentration of biological solutions and achieved 20-times concentration in human peritoneal dialysis effluent solution which enables the previously unattainable detection of proteins in these samples. We established a method for water removal as well as accurate water content measurement of fecal samples, which can be valuable for gut metabolome analysis.Taken together, lyophilization is a valuable tool for the preservation of biological samples with many advantages. We aim to draw attention to the wide range of possibilities offered by freeze drying in pre-clinical or basic research.

RAAS inhibitors directly reduce diabetes-induced renal fibrosis via growth factor inhibition.

KEY POINTS: Increased activation of the renin-angiotensin-aldosterone system (RAAS) and elevated growth factor production are of crucial importance in the development of renal fibrosis leading to diabetic kidney disease. The aim of this study was to provide evidence for the antifibrotic potential of RAAS inhibitor (RAASi) treatment and to explore the exact mechanism of this protective effect. We found that RAASi ameliorate diabetes-induced renal interstitial fibrosis and decrease profibrotic growth factor production. RAASi prevents fibrosis by acting directly on proximal tubular cells, and inhibits hyperglycaemia-induced growth factor production and thereby fibroblast activation. These results suggest a novel therapeutic indication and potential of RAASi in the treatment of renal fibrosis. ABSTRACT: In diabetic kidney disease (DKD) increased activation of renin-angiotensin-aldosterone system (RAAS) contributes to renal fibrosis. Although RAAS inhibitors (RAASi) are the gold standard therapy in DKD, the mechanism of their antifibrotic effect is not yet clarified. Here we tested the antifibrotic and renoprotective action of RAASi in a rat model of streptozotocin-induced DKD. In vitro studies on proximal tubular cells and renal fibroblasts were also performed to further clarify the signal transduction pathways that are directly altered by hyperglycaemia. After 5 weeks of diabetes, male Wistar rats were treated for two more weeks per os with the RAASi ramipril, losartan, spironolactone or eplerenone. Proximal tubular cells were cultured in normal or high glucose (HG) medium and treated with RAASi. Platelet-derived growth factor (PDGF) or connective tissue growth factor (CTGF/CCN2)-induced renal fibroblasts were also treated with various RAASi. In diabetic rats, reduced renal function and interstitial fibrosis were ameliorated and elevated renal profibrotic factors (TGFß1, PDGF, CTGF/CCN2, MMP2, TIMP1) and alpha-smooth muscle actin (αSMA) levels were decreased by RAASi. HG increased growth factor production of HK-2 cells, which in turn induced activation and αSMA production of fibroblasts. RAASi decreased tubular PDGF and CTGF expression and reduced production of extracellular matrix (ECM) components in fibroblasts. In proximal tubular cells, hyperglycaemia-induced growth factor production increased renal fibroblast transformation, contributing to the development of fibrosis. RAASi, even in non-antihypertensive doses, decreased the production of profibrotic factors and directly prevented fibroblast activation. All these findings suggest a novel therapeutic role for RAASi in the treatment of renal fibrosis.

Antidepressant effect in diabetes-associated depression: A novel potential of RAAS inhibition.

The incidence of depression doubles in diabetic patients and is associated with poor outcomes. Studies indicate that renin-angiotensin-aldosterone system inhibitors (RAASi) might relieve depression, however the mechanism of action is not well understood. We recently showed that angiotensin receptor blockers have antidepressant effects in experimental diabetes comorbid depression. Here we investigated whether all types of RAASi exhibit antidepressant and neuroprotective properties. Diabetes was induced by streptozotocin in adult male Wistar rats. After 5 weeks of diabetes, rats were treated per os with non-pressor doses of enalapril, ramipril, spironolactone or eplerenone for 2 weeks. Behavior was evaluated using forced swim test and open field test. Inflammatory response and brain-derived neurotrophic factor (BDNF) signaling were investigated in the hippocampus. Both ACEi and MR antagonists reversed diabetes-induced behavioral despair confirming their antidepressant-like effect. This may occur via alterations in hippocampal cytokine-mediated inflammatory response. Repressed BDNF production was restored by RAASi. Both ACEi and MR antagonists facilitated the BDNF-tropomyosin receptor kinase B-cAMP response element-binding protein signaling pathway as part of their neuroprotective effect. These data highlight the important benefits of ACEi and MR antagonists in the treatment of diabetes-associated depressive symptoms. Our novel findings support the link between diabetes comorbid depression, inflammation and repressed BDNF signaling. RAASi could provide new therapeutic options to improve the outcomes of both disorders.