Rationale: Neprilysin (NEP) is a major endogenous catabolic enzyme of amyloid β (Aβ). Previous studies have suggested that increasing NEP expression in animal models of Alzheimer's disease had an ameliorative effect. However, the underlying signaling pathway that regulates NEP expression remains unclear. The aryl hydrocarbon receptor (AhR) is a ligand-activated cytoplasmic receptor and transcription factor. Recent studies have shown that AhR plays essential roles in the central nervous system (CNS), but its physiological and pathological roles in regulating NEP are not entirely known.

Rationale: Acute kidney injury (AKI) is a clinical syndrome associated with a multitude of conditions. Although renal replacement therapy (RRT) remains the cornerstone of treatment for advanced AKI, its implementation can potentially pose risks and may not be readily accessible across all healthcare settings and regions. Elevated lactate levels are implicated in sepsis-induced AKI; however, it remains unclear whether increased lactate directly induces AKI or elucidates the underlying mechanisms.Methods: For human, the measurement of lactate in arterial blood gas is performed using the direct determination of L-lactate through an electrode oxidation method by a blood gas analyzer. For mice, enzyme-linked immunosorbent assay (ELISA) kits were employed to quantify the concentrations of lactate and AKI biomarkers in blood and cell supernatant. The mouse model of AKI was performed with a single intraperitoneal (i.p.) administration of lactate (30 mg/kg) and low-dose LPS (2 mg/kg) for 24 h. Proteomic analysis was conducted to identify lactylated proteins in kidney tissues. Techniques such as, immunoprecipitation, western blotting and immunofluorescence were used to evaluate the levels of HMGB1 lactylation, neutrophil extracellular traps (NETs)and to assess related molecular signaling pathways.Main results: Our findings indicate that lactate serves as an independent predictor of AKI in patients with acute decompensated heart failure (ADHF). We observed that co-administration of lactate with low-dose lipopolysaccharide (LPS) resulted in lactate overproduction, which subsequently elevated serum levels of creatinine (Cre) and blood urea nitrogen (BUN). Furthermore, the combined application of lactate and low-dose LPS was shown to provoke HMGB1 lactylation within renal tissues. Notably, pretreatment with HMGB1 small interfering RNA (siRNA) effectively diminished lactate-mediated HMGB1 lactylation and alleviated the severity of AKI. Additionally, lactate accumulation was found to enhance the expression levels of NETs in the bloodstream, with circulating NETs levels positively correlating with HMGB1 lactylation. Importantly, pre-administration of HMGB1 inhibitors (glycyrrhizin) or lactate dehydrogenase A (LDH-A) inhibitors (oxamate) reversed the upregulation of NETs induced by lactate and low-dose LPS in both the blood and polymorphonuclear neutrophils (PMNs) cell supernatant, thereby ameliorating AKI associated with lactate accumulation.Conclusions: These findings illuminate the role of lactate-mediated HMGB1 lactylation in inducing AKI in mice through the activation of the HMGB1-NETs signaling pathway.

Impaired renal function in atherosclerotic renovascular disease (ARD) may be the result of crosstalk between atherosclerotic renovascular stenosis and amplified oxidative stress, inflammation and fibrosis. Berberine (BBR) regulates cholesterol metabolism and exerts antioxidant effects. Accordingly, we hypothesized that BBR treatment may ameliorate ARD-induced kidney injury through its cholesterol-lowering effect and also suppression of the pathways involved in oxidative stress, inflammation and NFκB activation. Male rats were subjected to unilateral renal artery stenosis with silver-irritant coil, and then fed with 12-week hypercholesterolemic diet. Rats with renal artery stenosis were randomly assigned to two groups (n = 6 each) – ARD, or ARD+BBR – according to diet alone or in combination with BBR. Similarly, age-matched rats underwent sham operation and were also fed with hypercholesterolemic diet alone or in combination with BBR as two corresponding controls. Single-kidney hemodynamic metrics were measured in vivo with Doppler ultrasound to determine renal artery flow. The metrics reflecting hyperlipidemia, oxidative stress, renal structure and function, inflammation and NFκB activation were measured, respectively. Compared with control rats, ARD rats had a significant increase in urinary albumin, plasma cholesterol, LDL and thiobarbituric acid reactive substances (TBARS) and a significant decrease in SOD activity. When exposed to 12-week BBR, ARD rats had significantly lower levels in blood pressure, LDL, urinary albumin, and TBARS. In addition, there were significantly lower expression levels of iNOS and TGF-β in the ARD+BBR group than in the ARD group, with attenuated NFκB-DNA binding activity and down-regulated protein levels of subunits p65 and p50 as well as IKKβ. We conclude that BBR can improve hypercholesterolemia and redox status in the kidney, eventually ameliorating chronic renal injury in rats with ARD, and that BBR can act against proinflammatory and profibrotic responses through suppression of the NFκB signaling pathway.

Objective To evaluate the incidence, risk, or protective factors of acute kidney injury (AKI) in patients after cardiac surgery based on the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Methods A retrospective analysis of 2,575 patients undergoing their first documented cardiac surgery with cardiopulmonary bypass (CPB) was conducted. Perioperative variables were collected and analyzed. Univariate and multiple logistic regression models were used for determining the association between the development of AKI and risk factors. Multiple Cox-proportional hazards modeling was performed to evaluate the impact of AKI on the mortality in the intensive care unit and hospital length of stay. Results Of 2,575 patients, 931 (36%) developed AKI. A total of 30 (1.2%) patients required renal replacement therapy. In the multivariate analysis, mechanical ventilation duration (OR1.446, 95% CI 1.195-1.749, p<0.001), CPB duration of ≥110 min (OR 1.314, 95% CI 1.072-1.611, p=0.009), erythrocytes transfusion (OR 1.078, 95% CI 1.050-1.106, p<0.001), and postoperative body temperature greater than 38°C within 3 days (OR 1.234, 95% CI 1.018-1.496, p=0.032) were independent risk factors for CSA-AKI, while ulinastatin use was associated with a reduced incidence of CSA-AKI (OR 0.694, 95% CI 0.557-0.881, p=0.006). CSA-AKI was significantly associated with in-hospital mortality (adjusted HR: 2.218, 95% CI 1.161-4.238, p=0.016), especially in patients needing renal replacement therapy (adjusted HR: 18.683, 95% CI 8.579-40.684, p<0.001). Conclusion Mechanical ventilation duration, erythrocytes transfusion, and postoperative body temperature above 38°C within 3 days were considered independent risk factors for CSA-AKI. The use of ulinastatin was associated with a reduced incidence of CSA-AKI.

Stromal cell-derived factor-1(SDF-1) is a chemotactic and angiogenic factor that mediates the repair of various tissues. As macrophages are important contributors to ischemic kidney injury, we examine the role of SDF-1 in a rodent model of ischemia-reperfusion (I/R) injury. Male wild-type (WT) (C57BL/6) mice were subjected to bilateral I/R injury or sham operation in the presence or absence of macrophage depletion (liposomal clodronate [0.2 ml/20–25 g body weight i.p.]). Macrophage accumulation was assessed by immunohistochemistry. Tissue levels of SDF-1 (ELISA) and SDF-1 mRNA expression (real-time PCR) were measured. The cellular location of SDF-1 was assessed using immunohistochemical staining. Immunofluorescence staining of renal tissue sections confirmed macrophage depletion by liposomal clodronate. SDF-1 production was elevated in response to I/R injury and was significantly increased upon macrophage depletion. SDF-1 positive cells initially appeared initially in the cortex, and subsequently diffused to the outer medulla after I/R injury. Our study demonstrates that SDF-1 is significantly upregulated during renal I/R. We hypothesize that SDF-1 upregulation may be an important macrophage effector mechanism during I/R injury.