Corrigendum: Pharmacological Inhibition of Macrophage Toll-like Receptor 4/Nuclear Factor-kappa B Alleviates Rhabdomyolysis-induced Acute Kidney Injury

In patients with rhabdomyolysis, the overwhelming release of myoglobin into the circulation is the primary cause of kidney injury. Myoglobin causes direct kidney injury as well as severe renal vasoconstriction. An increase in renal vascular resistance (RVR) results in renal blood flow (RBF) and glomerular filtration rate (GFR) reduction, tubular injury, and acute kidney injury (AKI). The mechanisms that underlie rhabdomyolysis-induced AKI are not fully understood but may involve the local production of vasoactive mediators in the kidney. Studies have shown that myoglobin stimulates endothelin-1 (ET-1) production in glomerular mesangial cells. Circulating ET-1 is also increased in rats subjected to glycerol-induced rhabdomyolysis. However, the upstream mechanisms of ET-1 production and downstream effectors of ET-1 actions in rhabdomyolysis-induced AKI remain unclear. Vasoactive ET-1 is generated by ET converting enzyme 1 (ECE-1)-induced proteolytic processing of inactive big ET to biologically active peptides. The downstream ion channel effectors of ET-1-induced vasoregulation include the transient receptor potential cation channel, subfamily C member 3 (TRPC3). This study demonstrates that glycerol-induced rhabdomyolysis in Wistar rats promotes ECE-1-dependent ET-1 production, RVR increase, GFR decrease, and AKI. Rhabdomyolysis-induced increases in RVR and AKI in the rats were attenuated by post-injury pharmacological inhibition of ECE-1, ET receptors, and TRPC3 channels. CRISPR/Cas9-mediated knockout of TRPC3 channels attenuated ET-1-induced renal vascular reactivity and rhabdomyolysis-induced AKI. These findings suggest that ECE-1-driven ET-1 production and downstream activation of TRPC3-dependent renal vasoconstriction contribute to rhabdomyolysis-induced AKI. Hence, post-injury inhibition of ET-1-mediated renal vasoregulation may provide therapeutic targets for rhabdomyolysis-induced AKI.

Rhabdomyolysis is a life‐threatening condition resulting from the breakdown of skeletal muscle fibers leading to the release of myoglobin into the blood. Increased circulating myoglobin can cause kidney damage, and acute kidney injury (AKI) occurs in 33‐50% of patients with myoglobinuria. Persistent constriction of the renal microvessels, which reduces renal blood flow (RBF) and glomerular filtration rate (GFR), contributes to rhabdomyolysis‐induced AKI. Since activation of G‐protein‐coupled receptors (GPCR) and ion channels regulate renal vascular resistance (RVR), rhabdomyolysis may likely modulate RVR via GPCR and vascular ion channel mechanisms. Pretreatment of rats with an endothelin receptor antagonist has been shown to alleviate rhabdomyolysis‐induced AKI. However, the downstream and upstream links between rhabdomyolysis and increased ET‐1 synthesis are unknown. The downstream effectors of ET‐1‐induced vasoconstriction are smooth muscle cell (SMC) Ca2+‐permeable ion channels. Yet, the ion channel mechanisms that trigger renal vasoconstriction in rhabdomyolysis‐induced AKI remain unknown. Also, most cases of rhabdomyolysis‐induced AKI cannot be predicted. Whether post‐injury inhibition of the vascular mechanisms of ET‐1 ameliorates, rhabdomyolysis‐induced AKI is unknown. This study investigates post‐injury renal production and vascular regulation of the ET system in rhabdomyolysis‐induced AKI. Six h of rhabdomyolysis increased peptidase endothelin converting enzyme (ECE‐1)‐dependent biosynthesis of ET‐1 in the kidneys. Rhabdomyolysis‐induced AKI was not sex‐dependent. At 24 h, rhabdomyolysis also increased renal reactive oxygen species (ROS), ECE‐1, and ET‐1 levels. Furthermore, ET‐1 activated rat renal vascular smooth muscle cell TRPC3 leading to a reduction in RBF and increased RVR. Protein expression levels of the ET receptors (ETA and ETB) and TRPC3 channels in renal microvessels were unaltered. However, postinjury inhibition of ECE1, ET Receptors, and TRPC3 mitigated rhabdomyolysis‐induced GFR impairment, renal hypoperfusion, AKI biomarker elevation, and morphological kidney damage. To further explore the role of TRPC3 ion channels in rhabdomyolysis‐induced AKI, we subjected TRPC3 knock‐out (KO) rats to rhabdomyolysis. Compared to their wild‐type counterparts, KO rats show protection against rhabdomyolysis‐induced AKI. Our findings suggest that ECE‐driven proteolytic ET‐1 production contributes to rhabdomyolysis‐induced AKI. Downstream, ET‐derived DAG activates renal vascular smooth muscle cell TRPC3 channels leading to extracellular calcium entry, vasoconstriction, increased RVR, and reduced GFR.

BACKGROUND AND AIMS In rhabdomyolysis—characterized by massive striated muscle damage—main complication is Acute Kidney Injury (AKI) occurring in up to 50% cases. Physiopathology of rhabdomyolysis induced AKI (RIAKI) was historically described as the association of intrarenal vasoconstriction, tubular obstruction by myoglobin casts and direct tubular toxicity (by oxidative stress, lipid peroxidation). Recently, it became evident that the innate immunity also plays a role. Macrophages infiltrate contributes to direct tubular toxicity and we found activation of the complement system in patients and mice with RIAKI, in part mediated by myoglobin released heme [1]. Still, the mechanisms by which the innate immunity contribute to the RIAKI kidney injury and to which extend there are comparable to ischemia reperfusion injury (IRI) are not fully understood. METHOD We performed a kinetic model of glycerol (GLY) induced RIAKI in C57BL/6 mice at 1, 3, 12, 24 hours and 7 days and analysed kidney function (biochemical parameters, histology), injury markers (Quantigene: analyse simultaneously expression of 80 genes, chosen from RIAKI transcriptomic signature (1)), complement deposits (immunofluorescence). We evaluated the abundance of tissue-infiltrating immune and stromal cell populations using gene expression (MCP counter), validated by flow cytometry. Kinetic of expression of RIAKI genes was compared to scRNAseq of IRI model [2]. We compared WT mice to ones deficient of the classical (C1q–/–, C4–/–), alternative (C3–/– and FB–/–) and lectin (Collectin-11-/-) pathways. Finally, we analysed complement activation fragments in the urine of 15 RIAKI patients as compared to controls (n = 5) and IRI patients (n = 5). RESULTS Upon rhabdomyolysis, AKI in mice starts as early as 3 h post-GLY injection. Despite early upregulation of cytoprotective transcription factors (Maff, Myc, Sox9 within 3 h) and genes implicated in heme detoxification (HO1 and ferritin), both proximal and distal tubules are affected between 6 and 12 h post injury and endothelial injury is evident from 3 h. Granulocytes, monocytes and eosinophils increased in blood and infiltrated the kidney at 12 h due to preceding overexpression of chemoattractants (Cxcl1, Lgals3, Ccl2, Ccl7, Ccl12), likely by injured tubules. At 24 h, the phenotype of RIAKI kidney infiltrating inflammatory monocytes, eosinophils and resident macrophages revealed strong upregulation of C5aR1 (5x, 7x and 2x), while its levels in neutrophils tend to decrease, suggesting C5a-mediated activation. This was paralleled by intrarenal complement deposits on injured tubules and complement biomarkers in urine. To underscore the pathological relevance of complement, we found that alternative and to some extend lectin pathway deficient mice were partially protected, as opposed to mice deficient for classical pathway (Figure 1). Complement activation byproducts, notably Ba, C3a and C5a were increased in RIAKI patient urine as compared to control (including when normalized by proteinuria) (Figure 2). CONCLUSION The kinetic of RIAKI follows the pattern of IRI acute kidney injury with specificities regarding early response to heme overload. Despite numerous protective mechanisms initiated, kidney tubules and blood vessels are rapidly affected. This results in early kidney inflammation, complement deposition and chemoattraction of immune cell with complement responsive phenotype. Complement biomarkers are increased in urine of RIAKI mice and patients alike. Our study underlines the importance to study the first hours post injury to understand the mechanisms involved in order to propose specific treatment. Complement targeting has to be explored as a therapeutic strategy in this disease.

AMONG THE VARIOUS CAUSES OF acute kidney injury (AKI) in hospitalized patients, sepsis remains the most elusive and challenging for the practicing nephrologist. Decades of intensive basic, translational, and clinical research have failed to significantly alter the grim outcome of sepsis and sepsisinduced AKI (13). Nevertheless, active bench research continues to fuel the hope for successful therapies that will eventually

PurposeAcute kidney injury (AKI) secondary to Rhabdomyolysis syndrome represents a life-threatening complication, characterized by notably high incidence and mortality rates. The role of cellular senescence in the progression of AKI has increasingly garnered attention in recent years. Our previous research has demonstrated that remote ischemic postconditioning (RIPC) can attenuate renal cellular senescence and elevation of serum level of interleukin-6 (IL-6) induced by ischemia-reperfusion injury following crush injury. The objective of this study is to investigate the specific role of IL-6 in Rhabdomyolysis-induced AKI (RM-AKI).MethodsWe established a mouse model of RM-AKI by intramuscular injection of glycerol and simulated RM-AKI at the cellular level by treating Hk-2 cells with myoglobin. Tocilizumab (TCZ), a humanized monoclonal antibody against the interleukin-6 (IL-6) receptor, is a key substance. IL-6, a multifunctional cytokine, plays a crucial role in the occurrence and development of various kidney diseases. It can promote inflammatory responses, cell proliferation, fibrosis, and other processes. TCZ exerts a protective effect on the kidneys by specifically binding to the IL-6 receptor and blocking the signal transduction of IL-6. Additionally, the levels of IL-6 were detected by employing ELISA kits. RNA sequencing analysis was performed on cells treated with myoglobin and tocilizumab. Flow cytometry was utilized to assess cell cycle distribution and the percentage of senescent cells. The expression levels of SERPINE1, GATA2, p53, and p21 were determined by real-time quantitative PCR and Western blot. Additionally, a dual-luciferase reporter gene assay was conducted to validate the binding effect of SERPINE1 and GATA2.ResultsTranscriptome Analysis revealed that genes including GATA2 and SERPINE1 were downregulated in HK-2 cells following tocilizumab treatment. Inhibition of the IL-6 receptor by tocilizumab in these cells led to a reduction in cellular senescence, accompanied by decreased of the cell cycle regulatory proteins P53 and P21 in mRNA and protein levels, while alleviating cell cycle arrest. Additionally, a dual-luciferase reporter assay confirmed that GATA2 binds to the promoter of SERPINE1 (PAI-1), thereby initiating its transcription.ConclusionThe IL-6/GATA2/SERPINE1 pathway mediates cellular senescence after acute kidney injury, and inhibiting IL-6 can alleviate AKI-induced cellular senescence, providing an important basis for exploring new therapeutic strategies.

Inhibition of cytochrome P450 2E1 and activation of transcription factor Nrf2 are renoprotective in myoglobinuric acute kidney injury

SUN-173 COMPARISON BETWEEN RHABDOMYOLYSIS INDUCED AND SEPTIC ACUTE KIDNEY INJURY

The development of chronic kidney disease (CKD) following an episode of acute kidney injury (AKI) is an increasingly recognized clinical problem. Inhibition of toll-like receptor 4 (TLR4) protects renal function in animal models of AKI and has become a viable therapeutic strategy in AKI. However, the impact of TLR4 inhibition on the chronic sequelae of AKI is unknown. Consequently, we examined the chronic effects of TLR4 inhibition in a model of ischemic AKI. Mice with a TLR4-deletion on a C57BL/6 background and wild-type (WT) background control mice (C57BL/6) were subjected to bilateral renal artery clamping for 19 min and reperfusion for up to 6 weeks. Despite the acute protective effect of TLR4 inhibition on renal function (serum creatinine 1.6 ± 0.4 mg/dL TLR4-deletion vs. 2.8 ± 0.3 mg/dL·WT) and rates of tubular apoptosis following ischemic AKI, we found no difference in neutrophil or macrophage infiltration. Furthermore, we observed significant protection from microvascular rarefaction at six weeks following injury with TLR4-deletion, but this did not alter development of fibrosis. In conclusion, we validate the acute protective effect of TLR4 signal inhibition in AKI but demonstrate that this protective effect does not mitigate the sequential fibrogenic response in this model of ischemic AKI.

Background: Acute kidney injury (AKI) is a common complication of acute disease which can cause long-term renal and cardiovascular disease. Women have been excluded from these studies as men and the elderly are considered higher risk, which creates a significant gap in our knowledge of the risk of young women for AKI. Young people are more likely to have rhabdomyolysis-induced AKI (RIAKI) due to muscle injury sustained during exercise, combat, and other accidents and are more likely to survive such incidents; therefore, RIAKI is relevant to understanding long-term reproductive impact of AKI. Using a mouse model of RIAKI, we observed that recovered pre-pregnancy parental AKI resulted in later pregnancy complications, including reduced maternal GFR, increased maternal renal fibrosis, and albuminuria, as well as fetal impact including perinatal death and fetal growth restriction. Studies of offspring following other pregnancy complications indicate underdeveloped organs, including the kidney, resulting in adult-onset disease. We hypothesized that RIAKI-related pregnancy complications would cause developmental programming of adult renal disease in the offspring. Methods: Procedures were approved by institutional IACUC. RIAKI was generated via intramuscular injection of 50% glycerol (8 mL/kg) in 8-10 week old C57BL/6 male and female mice while shams were untreated. After documenting recovery from AKI (return to normal glomerular filtration rate (GFR; uL/min/100g body weight)) 2 weeks post-treatment, sham/sham and RIAKI/RIAKI pairings (n=5 each) were established. Pups survived for either 6 months (young adulthood) or 1 year (older adulthood) and weighed weekly for the first 12 weeks, then again at sacrifice. Urine was collected 24h before GFR measurement and collection of blood, heart, and kidneys. Blood pressures were measured at 6 months for 3 days by tail cuff plethysmography. Sodium and potassium were measured by flame emission detection. Retinol binding protein 4 (RBP4), a measure of proximal tubule dysfunction, was assessed by ELISA. Statistics were assessed by one-way ANOVA with post hoc tests. Results: Pups from RIAKI pairs were born smaller (p=0.006) and remained smaller 1 week after birth (p=0.02) regardless of sex, but were significantly similar to sham offspring at 2-12 weeks. Males from RIAKI pairs gained significantly more weight between 6 and 12 months than females (p=0.04); female RIAKI offspring did not differ from shams. Both males and females from RIAKI pairs had reduced GFR compared to shams at 6 months (p=0.02, p=0.02), but only males were affected at 12 months (p=0.03). However, no changes were observed between groups in systolic, diastolic, or mean arterial pressures at 6 months, nor were there differences in sodium or potassium excretion. RBP4 was unchanged in 6 or 12 month urine samples. Heart weight or kidney weight to body weight ratios were not different except kidney weight/body weight was smaller in female offspring of RIAKI pairs compared to shams at 6 months (p=0.04). Conclusions: Offspring of parents with recovered AKI show evidence of programming for renal disease despite never having AKI themselves. RBP4, sodium, and potassium excretion remaining unchanged suggest that this may be due to reduced availability of glomeruli and nephrons rather than tubule dysfunction. Body weight changes in males but not females, and kidney weight differences in females but not males, indicate sex differences in programmed dysfunction, including possible edema in males. Further studies will evaluate body composition, analysis of fecal and urine content, and renal histology. JFH is supported by the NIH NCATS KL2 (KL2TR002370) and the AHA CDA (24CDA1269587). MPH is supported by DOD (W81XWH2010196) and VA Merit (1I01BX004288). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Rhabdomyolysis is a risk factor for acute kidney injury, transition towards chronic kidney disease, and death. The role of calcium phosphate deposits in the mechanisms of rhabdomyolysis-induced acute kidney injury (RAKI) is still unclear. Better insight of the role calcium in RAKI could lead to new therapeutic avenues. Here, we show in a mice model of RAKI that calcium phosphate deposits were frequent in the kidney (hydroxyapatite) and partly correlated with the severity of the kidney injury. However, the intensity of deposits was highly heterogeneous between mice. Treatment with sodium chloride, sodium bicarbonate or inorganic pyrophosphate (PPi; an inhibitor of the calcium phosphate crystallization), or combinations thereof, did not improve kidney outcomes and hydroxyapatite deposition during RAKI. Unexpectedly, Abcc6 knockout mice (ko), characterized by PPi deficiency, developed less severe RAKI despite similar rhabdomyolysis severity, and had similar hydroxyapatite deposition suggesting alternative mechanisms. This improved kidney outcome at day 2 translated to a trend in improved glomerular filtration rate at month 2 in Abcc6-/-mice and to significantly less interstitial fibrosis. In addition, whereas the pattern of infiltrating cells at day 2 was similar between wt and ko mice, kidneys of Abcc6-/- mice were characterized by more CD19+ B-cells, less CD3+ T-cells and a lower R1/R2 macrophage ratio at month 2. In summary, kidney calcium phosphate deposits are frequent in RAKI but hydration with sodium bicarbonate or sodium chloride does not modify the kidney outcome. Blocking ABCC6 emerges as a new option to prevent RAKI and subsequent transition toward kidney fibrosis.

Tubular mitochondrial pyruvate carrier disruption elicits redox adaptations that protect from acute kidney injury

An early experience on the effect of solid organ transplant status on hospitalized COVID-19 patients.

Advanced glycation endproducts (AGEs) contribute to cellular damage of various pathologies, including kidney diseases. Acute kidney injury (AKI) represents a syndrome seldom characterized by a single, distinct pathophysiological cause. Rhabdomyolysis-induced acute kidney injury (RIAKI) constitutes roughly 15% of AKI cases, yet its underlying pathophysiology remains poorly understood. Using a murine model of RIAKI induced by muscular glycerol injection, we observed elevated levels of AGEs and the AGE receptor galectin-3 (LGALS3) in the kidney. Immunofluorescence localized LGALS3 to distal nephron segments. According to transcriptomic profiling via next-generation sequencing, RIAKI led to profound changes in kidney metabolism, oxidative stress, and inflammation. Cellular stress was evident in both proximal and distal tubules, as shown by kidney injury markers KIM-1 and NGAL. However, only proximal tubules exhibited overt damage and apoptosis, as detected by routine morphology, active Caspase-3, and TUNEL assay, respectively. In vitro, distal convoluted tubule (DCT) cells challenged with AGEs underwent apoptosis, which was markedly enhanced by Lgals3 siRNA treatment. Thus, in RIAKI, the upregulation of LGALS3 may protect the distal nephron from AGE-mediated damage, while proximal tubules lacking LGALS3 stay at risk. Thus, stimulating LGALS3 in the proximal nephron, if achievable, may attenuate RIAKI.

Introduction: Acute kidney injury (AKI) is rapidly increasing in global incidence and a healthcare burden. Prior maternal AKI diagnosis correlates with later pregnancy complications. As pregnancy influences developmental programming, we hypothesized that recovered parental AKI results in poor pregnancy outcomes, impaired fetal growth, and adult offspring disease. Methods: Using a well-characterized model of rhabdomyolysis-induced acute kidney injury (RIAKI), a form of AKI commonly observed in young people, we confirmed functional renal recovery by assessing glomerular filtration rate (GFR) 2weeks following RIAKI. We bred sham and recovered RIAKI sires and dams in timed, matched matings for gestational day (GD) 16.5 and offspring (birth-12weeks, 6months) study. Results: Despite a normal GFR pre-pregnancy, recovered RIAKI dams at GD16.5 had impaired renal function, resulting in reduced fetoplacental ratios and offspring survival. Pregnant RIAKI dams also had albuminuria and less renal megalin in the proximal tubule brush border than shams, with renal subcapsular fibrosis and higher diastolic blood pressure. Growth-restricted offspring had a reduced GFR as older adults, with evidence of metabolic inefficiency in male offspring; this correlated with reduced renal AngII levels in female offspring from recovered RIAKI pairings. However, the blood pressures of 6-month-old offspring were unaffected by parental RIAKI. Conclusions: Our mouse model demonstrated a causal relationship among RIAKI, gestational risk, and developmental programming of the adult-onset offspring GFR and metabolic dysregulation despite parental recovery.

Do Children With Acute Kidney Injury Require Long-term Evaluation for CKD?