Unveiling the potential of mitochondrial dynamics as a therapeutic strategy for acute kidney injury

Combined sedentarism and high-fat diet induce early signs of kidney injury in C57BL/6J mice

Chronic kidney disease (CKD) is a progressive disorder marked by a decline in kidney function. Obesity and sedentary behavior contribute to the development of CKD, though mechanisms by which this occurs are poorly understood. This knowledge gap is worsened by the lack of a reliable murine CKD model that does not rely on injury, toxin, or gene deletion to induce a reduction in kidney function. High-fat diet (HFD) feeding alone is insufficient to cause reduced kidney function until later in life. Here, we used a small mouse cage (SMC), a recently developed mouse model of sedentariness, to study its effect on kidney function. Wild-type C57BL/6J male mice were housed in sham or SMC housing for 6 mo with HFD in room (22°C) or thermoneutral (30°C) conditions. Despite hyperinsulinemia induced by the SMC + HFD intervention, kidneys from these mice displayed normal glomerular filtration rate. However, the kidneys showed early signs of kidney injury, including increases in collagen I and neutrophil gelatinase-associated lipocalin transcripts, as well as fibrosis by histology, primarily in the inner medullary/papilla region. High-resolution respirometry and fluorometry experiments showed no statistically significant changes in the capacities for respiration, ATP synthesis, or electron leak. These data confirm the technical challenge in modeling human CKD. They further support the notion that obesity and a sedentary lifestyle make the kidneys more vulnerable, but additional insults are likely required for the pathogenesis of CKD.NEW & NOTEWORTHY Physical inactivity is a risk factor for chronic kidney disease. Our laboratory recently developed a new mouse model of physical inactivity (small mouse cage housing) that more closely recapitulates the metabolic disturbances that occur with sedentary behavior. In this paper, we performed an in-depth phenotyping of kidney function and metabolic parameters in response to small mouse cage housing.

Augmenter of liver regeneration (ALR) can regulate iron homeostasis through the INOS/NO/SLC39A14 pathway to reduce ferroptosis in acute kidney injury

Acute kidney injury (AKI) is a complex clinical syndrome that affects approximately 13.3 million people worldwide each year. Although ferroptosis has been implicated in the pathological progression of AKI, the underlying mechanisms remain elusive. Augmenter of liver regeneration (ALR) plays a role in apoptosis, autophagy and oxidative stress induction in renal tubular epithelial cells; however, the specific mechanisms through which ALR is involved in AKI are unclear. The present study investigated the effects of ALR on regulating iron uptake and ferroptosis in AKI under in vivo and in vitro conditions. Renal tubular epithelial cell-specific Alr knockout (AlrKO) mice and ischaemia/reperfusion (I/R)-induced AKI in vivo models were generated. ALR overexpression and hypoxia/reoxygenation (H/R)-induced AKI in vitro models were generated using human renal tubular epithelial cells. The effects of ALR on ferroptosis and kidney function in AKI were investigated through in vitro and in vivo studies involving biochemical analysis, RT-qPCR, western blotting assay, immunofluorescence assay, and transmission electron microscopy. Transcriptome sequencing, iron homeostasis, and inducible nitric oxide synthase (iNOS)/nitric oxide (NO) synthesis detection were performed to investigate the mechanisms through which ALR affects AKI. Loss-of-function experiments revealed that kidney tubule-specific Alr knockout in mice exacerbated iron uptake, ferroptosis, and acute kidney I/R injury. Mechanistically, we found that ALR could regulate iron homeostasis through the iNOS/NO/Solute carrier family 39 member 14 (SLC39A14) pathway to reduce ferroptosis in AKI. The results of this study reveal a previously undescribed function of ALR in iron homeostasis and ferroptosis in AKI, and suggest that targeting ALR could be a potential treatment option for AKI.

Mitochondria-targeting therapeutic strategies for chronic kidney disease

Chronic kidney disease (CKD) is a multifactorial health issue characterised by kidney impairment that has significant morbidity and mortality in the global population. Current treatments for CKD fail to prevent progression to end-stage kidney disease, where management is limited to renal replacement therapy or kidney transplantation. Mitochondrial dysfunction has been implicated in the pathogenesis of CKD and can be broadly categorised into abnormalities related to excessive oxidative stress, reduced mitochondrial biogenesis, excess mitochondrial fission and dysregulated mitophagy. Mitochondria-targeting therapeutic strategies target many of the outlined mechanisms of mitochondrial dysfunction, and an overview of recent evidence for mitochondria-targeting therapeutic strategies is explored in this review, including naturally derived compounds and novel approaches such as fusion proteins. Mitochondria-targeting therapeutic strategies using these approaches show the potential to stabilise or improve renal function, and clinical studies are needed to further confirm their safety and efficacy in human contexts.

Mechanism study of YangJing ZhongYu decoction on regulating mitochondrial dynamics of ovarian granular cells and improving diminished ovarian reserve

OBJECTIVE

Diminished ovarian reserve (DOR) encompasses both reproductive and endocrine disorders, resulting in a decline in female fertility. This paper explored the mechanism of Yangjing Zhongyu Decoction (YJZYD) regulating mitochondrial dynamics of ovarian granulosa cells (GCs) to improve DOR.

METHODS

DOR patients were treated with YJZYD, with ovarian volume (OV), antral follicle count (AFC), and endometrial thickness (EMT) detected. C57BL/6 female mice were treated by cyclophosphamide (Cy) intraperitoneal injection and YJZYD solution daily gavage, with serum anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) levels determined. Ovarian GCs (KGN) were interfered with 4-Hydroperoxy-Cyclophosphamide (4-HC) and treated with the MAPK/ERK pathway inhibitor or activator.

RESULTS

DOR patients showed increased levels of serum AMH, E2, OV, AFC and EMT, while reduced FSH and LH levels after YJZYD treatment. After Cy induction, DOR mice exhibited irregular estrous cycles, diminished serum AMH and E2 levels, elevated FSH and LH levels, reduced follicle number and atresia follicle number, disorderly arranged GCs, and severe interstitial fibrosis. After 4-HC treatment, KGN proliferation and Bcl-2, MFN1, and MFN2 were suppressed, while apoptotic rate, Bax, Cleaved-caspase-3, and p-Drp1 (Ser616) levels, and mitochondrial fission and quantity increased. YJZYD promoted 4-HC-treated KGN proliferation, boosted mitochondrial fusion, and inhibited apoptosis and mitochondrial fission via the MAPK/ERK pathway.

CONCLUSION

YJZYD promoted ovarian GC proliferation and mitochondrial fusion, suppressed cell apoptosis and mitochondrial fission, and effectively improved DOR in mice by activating the MAPK/ERK pathway, providing a theoretical basis for the clinical application value of YJZYD in DOR treatment.

Six months of physical inactivity is insufficient to cause chronic kidney disease in C57BL/6J mice

Chronic kidney disease (CKD) is a progressive disorder marked by a decline in kidney function. Obesity and sedentary behavior contribute to the development of CKD, though mechanisms by which this occurs are poorly understood. This knowledge gap is worsened by the lack of a reliable murine CKD model that does not rely on injury, toxin, or gene deletion to induce a reduction in kidney function. High-fat diet (HFD) feeding alone is insufficient to cause reduced kidney function until later in life. Here, we employed a small mouse cage (SMC), a recently developed mouse model of sedentariness, to study its effect on kidney function. Wildtype C57BL/6J male mice were housed in sham or SMC housing for six months with HFD in room (22°C) or thermoneutral (30°C) conditions. Despite hyperinsulinemia induced by the SMC+HFD intervention, kidneys from these mice displayed normal glomerular filtration rate (GFR). However, the kidneys showed early signs of kidney injury, including increases in Col1a1 and NGAL transcripts, as well as fibrosis by histology, primarily in the inner medullary/papilla region. High-resolution respirometry and fluorometry experiments showed no statistically significant changes in the capacities for respiration, ATP synthesis, or electron leak. These data confirm the technical challenge in modeling human CKD. They further support the notion that obesity and a sedentary lifestyle make the kidneys more vulnerable, but additional insults are likely required for the pathogenesis of CKD.

Dual therapy with phospholipase and metalloproteinase inhibitors from Sinonatrix annularis alleviated acute kidney and liver injury caused by multiple snake venoms

Snakebite envenomation often induces acute kidney injury (AKI) and acute liver injury (ALI), leading to augmented injuries and poor rehabilitation. Phospholipase A2 (PLA2) and metalloproteinase (SVMP) present in venom are responsible for the envenomation-associated events. In this study, mice envenomed with Deinagkistrodon acutus, Naja atra, or Agkistrodon halys pallas venom exhibited typical AKI and ALI symptoms, including significantly increased plasma levels of myoglobin, free hemoglobin, uric acid, aspartate aminotransferase, and alanine aminotransferase and upregulated expression of kidney NGAL and KIM-1. These effects were significantly inhibited when the mice were pretreated with natural inhibitors of PLA2 and SVMP isolated from Sinonatrix annularis (SaPLIγ and SaMPI). The inhibitors protected the physiological structural integrity of the renal tubules and glomeruli, alleviating inflammatory infiltration and diffuse hemorrhage in the liver. Furthermore, the dual therapy alleviated oxidative stress and apoptosis in the kidneys and liver by mitigating mitochondrial damage, thereby effectively reducing the lethal effect of snake venom in the inhibitor-treated mouse model. This study showed that dual therapy with inhibitors of metalloproteinase and phospholipase can effectively prevent ALI and AKI caused by snake bites. Our findings suggest that intrinsic inhibitors present in snakes are prospective therapeutic agents for multi-organ injuries caused by snake envenoming.

New insights into the spleen injury by mitochondrial dysfunction of chicken under polystyrene microplastics stress

Microplastics biological toxicity, environmental persistence and biological chemicals have been paid widespread attention. Microplastics exposed to chicken spleen injury of the specific mechanism is unclear. Thus, we randomly assigned chickens to 4 groups: C (normal diet), L-MPs (1 mg/L), M-MPs (10 mg/L), and H-MPs (100 mg/L), and assessed spleen damage after 42 d of exposure. Morphologically, the boundary between the red and white pulp of the spleen was blurred, along with the expansion of the white pulp. It was further speculated that microplastics induced mitochondrial dynamic homeostasis (Drp1 upgraded, Mfn1, Mfn2, and OPA1 reduced), and provoked the mitochondrial apoptotic pathway (Bcl-2/Bax decreased, cytc, caspase3, and caspase9 raised), resulting in redox imbalance and lipid peroxide accumulation (MDA increased, CAT, GSH, and T-AOC plummeted), and further stimulated ferroptosis (FTH1, GPX4, and SLC7A11 decreased). Here we explored the impact of polystyrene microplastics on the spleen, as well as the programmed death (apoptosis and ferroptosis) involved, and the regulative role of mitochondria in this process. This could be of significant importance in bridging the gap in laboratory research on microplastics-induced spleen injury in chicken.

Molecular Mechanisms of Oxidative Stress in Acute Kidney Injury: Targeting the Loci by Resveratrol

Reactive oxygen species are a group of cellular molecules that stand as double-edged swords, their good and bad being discriminated by a precise balance. Several metabolic reactions in the biological system generate these molecules that interact with cellular atoms to regulate functions ranging from cell homeostasis to cell death. A prooxidative state of the cell concomitant with decreased clearance of such molecules leads to oxidative stress, which contributes as a prime pathophysiological mechanism in various diseases including renal disorders, such as acute kidney injury. However, targeting the generation of oxidative stress in renal disorders by an antioxidant, resveratrol, is gaining considerable therapeutic importance and is known to improve the condition in preclinical studies. This review aims to discuss molecular mechanisms of oxidative stress in acute kidney injury and its amelioration by resveratrol. The major sources of data were PubMed and Google Scholar, with studies from the last five years primarily included, with significant earlier data also considered. Mitochondrial dysfunction, various enzymatic reactions, and protein misfolding are the major sources of reactive oxygen species in acute kidney injury, and interrupting these loci of generation or intersection with other cellular components by resveratrol can mitigate the severity of the condition.