Caspase-3 Is a Pivotal Regulator of Microvascular Rarefaction and Renal Fibrosis after Ischemia-Reperfusion Injury

Calcium signaling crosstalk between the endoplasmic reticulum and mitochondria, a new drug development strategies of kidney diseases

Calcium (Ca2+) acts as a second messenger and constitutes a complex and large information exchange system between the endoplasmic reticulum (ER) and mitochondria; this process is involved in various life activities, such as energy metabolism, cell proliferation and apoptosis. Increasing evidence has suggested that alterations in Ca2+ crosstalk between the ER and mitochondria, including alterations in ER and mitochondrial Ca2+ channels and related Ca2+ regulatory proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), inositol 1,4,5-trisphosphate receptor (IP3R), and calnexin (CNX), are closely associated with the development of kidney disease. Therapies targeting intracellular Ca2+ signaling have emerged as an emerging field in the treatment of renal diseases. In this review, we focused on recent advances in Ca2+ signaling, ER and mitochondrial Ca2+ monitoring methods and Ca2+ homeostasis in the development of renal diseases and sought to identify new targets and insights for the treatment of renal diseases by targeting Ca2+ channels or related Ca2+ regulatory proteins.

Traditional Chinese Medicine and renal regeneration: experimental evidence and future perspectives

Repair of acute kidney injury (AKI) is a typical example of renal regeneration. AKI is characterized by tubular cell death, peritubular capillary (PTC) thinning, and immune system activation. After renal tubule injury, resident renal progenitor cells, or renal tubule dedifferentiation, give rise to renal progenitor cells and repair the damaged renal tubule through proliferation and differentiation. Mesenchymal stem cells (MSCs) also play an important role in renal tubular repair. AKI leads to sparse PTC, affecting the supply of nutrients and oxygen and indirectly aggravating AKI. Therefore, repairing PTC is important for the prognosis of AKI. The activation of the immune system is conducive for the body to clear the necrotic cells and debris generated by AKI; however, if the immune activation is too strong or lengthy, it will cause damage to renal tubule cells or inhibit their repair. Macrophages have been shown to play an important role in the repair of kidney injury. Traditional Chinese medicine (TCM) has unique advantages in the treatment of AKI and a series of studies have been conducted on the topic in recent years. Herein, the role of TCM in promoting the repair of renal injury and its molecular mechanism is discussed from three perspectives: repair of renal tubular epithelial cells, repair of PTC, and regulation of macrophages to provide a reference for the treatment and mechanistic research of AKI.

The SP1/SIRT1/ACLY signaling axis mediates fatty acid oxidation in renal ischemia-reperfusion-induced renal fibrosis

BACKGROUND

Renal ischemia-reperfusion is the primary cause of acute kidney injury (AKI). Clinically, most patients who experience ischemia-reperfusion injury eventually progress gradually to renal fibrosis and chronic kidney disease (CKD). However, the underlying mechanism for AKI to CKD transition remain absent. Our study demonstrated that the downregulation of sirtuin 1 (Sirt1)-mediated fatty acid oxidation (FAO) facilitates IRI-induced renal fibrosis.

METHODS

The IRI animal model was established, and ribonucleic acid (RNA) sequencing was used to explore potential differentially expressed genes (DEGs) and pathways. The SIRT1 knockout mice were generated, and a recombinant adeno-associated virus that overexpresses SIRT1 was injected into mice to explore the function of SIRT1 in renal fibrosis induced by renal IRI. In vitro, hypoxia/reoxygenation (H/R) was used to establish the classical model of renal IRI and overexpression or knockdown of SIRT1 to investigate the SIRT1 function through lentiviral plasmids. The underlying molecular mechanism was explored through RNA sequencing, bioinformatics analysis, and chromatin immunoprecipitation assay.

RESULTS

RNA sequencing analysis and western blot demonstrated that the expression of SIRT1 was significantly decreased in IRI mice. Overexpression of SIRT1 improved renal function and reduced lipid deposition and renal fibrosis. On the contrary, knockout of SIRT1 aggravated kidney injury and renal fibrosis. RNA sequencing, bioinformatics analysis, and chromatin immunoprecipitation assay mechanistically revealed that SIRT1 impairs the acetylation of histone H3K27 on the promoter region of ACLY, thereby impeding FAO activity and promoting renal fibrosis. Additionally, SP1 regulated FAO by directly modulating SIRT1 expression.

CONCLUSION

Our findings highlight that downregulation of SIRT1-modulated FAO facilitated by the SP1/SIRT1/ACLY axis in the kidney increases IRI, suggesting SIRT1 to be a potential therapeutic target for renal fibrosis induced by renal IRI.

Downregulation of IL-1β/p38 mitogen activated protein kinase pathway by diacerein protects against kidney ischemia/reperfusion injury in rats

Renal ischemia-reperfusion (I/R) can be precipitated by multiple clinical situations that lead to impaired renal function and associated mortality. The resulting tubular cell damage is the outcome of complex disorders including, an inflammatory process with an overproduction of cytokines. Here, diacerein (DIA), an inhibitor of proinflammatory cytokine interleukin-1 beta (IL-1β), was investigated against renal I/R in rats. DIA was orally administrated (50 mg/kg/day) for ten days before bilateral ischemia for 45 min with subsequent 2 hr. reperfusion. Interestingly, DIA alleviated the renal dysfunction and histopathological damage in the renal tissues. Pretreatment with DIA corrected the oxidative imbalance by prevented reduction in antioxidant levels of GSH and SOD, while it decreased the elevation of the oxidative marker, MDA. In addition, DIA downregulated IL-1β and TNF-α expression in the renal tissues. Consequent to inhibition of the oxidative stress and inflammatory cascades, DIA inhibited the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK). Therefore, downstream targets for p38 MAPK were also inhibited via DIA which prevented further increases of inflammatory cytokines and the apoptotic marker, caspase-3. Collectively, this study revealed the renoprotective role of DIA for renal I/R and highlighted the role of p38 MAPK encountered in its therapeutic application in renal disease.

The therapeutic effect of Picroside II in renal ischemia-reperfusion induced acute kidney injury: An experimental study

The microcirculation hemodynamics change and inflammatory response are the two main pathophysiological mechanisms of renal ischemia-reperfusion injury (IRI) induced acute kidney injury (AKI). The treatment of microcirculation hemodynamics and inflammatory response can effectively alleviate renal injury and correct renal function. Picroside II (P II) has a wide range of pharmacological effects. Still, there are few studies on protecting IRI-AKI, and whether P II can improve renal microcirculation perfusion is still being determined. This study aims to explore the protective effect of P II on IRI-AKI and evaluate its ability to enhance renal microcirculation perfusion. In this study, a bilateral renal IRI-AKI model in mice was established, and the changes in renal microcirculation and inflammatory response were quantitatively evaluated before and after P II intervention by contrast-enhanced ultrasound (CEUS). At the same time, serum and tissue markers were measured to assess the changes in renal function. The results showed that after P II intervention, the levels of serum creatinine (Scr), blood urea nitrogen (BUN), serum cystatin C (Cys-C), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), malondialdehyde (MDA), and superoxide dismutase (SOD), as well as the time-to-peak (TTP), peak intensity (PI) and area under the curve (AUC), and the normalized intensity difference (NID) were all alleviated. In conclusion, P II can improve renal microcirculation perfusion changes caused by IRI-AKI, reduce inflammatory reactions during AKI, and enhance renal antioxidant stress capacity. P II may be a new and promising drug for treating IRI-AKI.

Remimazolam attenuates inflammation and kidney fibrosis following folic acid injury

The transition of acute kidney injury (AKI) to chronic kidney disease (CKD) is characterized by intense inflammation and progressive fibrosis. Remimazolam is widely used for procedural sedation in intensive care units, such as AKI patients. Remimazolam has been shown to possess anti-inflammatory and organ-protective properties. However, the role of remimazolam in inflammation and renal fibrosis following AKI remains unclear. Here, we explored the effects of remimazolam on the inflammatory response and kidney fibrogenesis of mice subjected to folic acid (FA) injury. Our results showed that remimazolam treatment alleviated kidney damage and dysfunction. Mice treated with remimazolam presented less collagen deposition in FA-injured kidneys compared with FA controls, which was accompanied by a reduction of extracellular matrix proteins accumulation and fibroblasts activation. Furthermore, remimazolam treatment reduced inflammatory cells infiltration into the kidneys of mice with FA injury and inhibited proinflammatory or profibrotic molecules expression. Finally, remimazolam treatment impaired the activation of bone marrow-derived fibroblasts and blunted the transformation of macrophages to myofibroblasts in FA nephropathy. Additionally, the benzodiazepine receptor antagonist PK-11195 partially reversed the protective effect of remimazolam on the FA-injured kidneys. Overall, remimazolam attenuates the inflammatory response and renal fibrosis development following FA-induced AKI, which may be related to the peripheral benzodiazepine receptor pathway.

Lrg1 silencing attenuates ischemia-reperfusion renal injury by regulating autophagy and apoptosis through the TGFβ1- Smad1/5 signaling pathway

BACKGROUND

Dysfunction in the processes of autophagy and apoptosis within renal tubular epithelial cells (RTEc) contributes to renal ischemia-reperfusion injury (IRI). However, the factors influencing this dysfunction remain unclear. Leucine-rich alpha-2-glycoprotein 1 (Lrg1) plays a role in the progression of diabetic nephropathy and kidney fibrosis by modulating the activin receptor-like kinase 1 (ALK1)-Smad1/5/8 and TGF-β1/Smad3 pathways, respectively. Therefore, we aimed to investigate whether Lrg1 is involved in the pathological mechanisms of renal IRI and whether its effects are related to the dysregulation of autophagy and apoptosis in RTEc.

METHODS

We conducted in vitro and in vivo experiments using CoCl2-induced hypoxic human kidney-2 (HK-2) cells and mice with renal IRI, respectively. Lrg1 was silenced using siRNA and lentiviral vectors in HK-2 cells and mouse kidneys. Rapamycin (Rapa) and methyladenine were applied to regulate autophagy in renal IRI models.

RESULTS

Increased Lrg1 expression was observed in hypoxic HK-2 cells and in the kidneys of mice with renal IRI. Silencing of Lrg1 through siRNA and lentiviral approaches restored autophagy and suppressed apoptosis in CoCl2-induced hypoxic HK-2 cells and renal IRI models. Additionally, reduced Lrg1 expression alleviated kidney damage caused by renal IRI. The downregulation of Lrg1 expression restrained the TGFβ-Smad1/5 signaling pathway in hypoxic-induced HK-2 cells and renal IRI by reducing ALK1 expression. Lastly, the enhancement of autophagy, achieved through Rapa treatment, provided protection against renal IRI in mice.

CONCLUSIONS

Our findings suggest that Lrg1 silencing can be applied as a potential therapeutic target to inhibit the TGFβ1-Smad1/5 pathway, thereby enhancing autophagy and decreasing apoptosis in patients with acute kidney injury.

BREAKING NEW GROUND: STANDARDIZING RAT MODELS FOR CRUSH SYNDROME INVESTIGATIONS

ABSTRACT

Crush syndrome (CS), alternatively termed traumatic rhabdomyolysis, is a paramount posttraumatic complication. Given the infeasibility of conducting direct simulation research in humans, the role of animal models is pivotal. Regrettably, the dearth of standardized animal models persists. The objective of this study was to construct a repeatable standardized rat CS models and, based on this, simulate specific clinical scenarios. Methods: Using a self-developed multichannel intelligent small-animal crush injury platform, we applied a force of 5 kg to the hind limbs of 8-week-old rats (280-300 g), subjecting them to a continuous 12 h compression to establish the CS model. Continuous monitoring was conducted for both the lower limbs and the overall body status. After decompression, biochemical samples were collected at 3, 6, 12, and 24 h. In addition, we created a CS model after resection of the left kidney (UNx-CS), which was conceptualized to simulate a more challenging clinical scenario to investigate the physiological and pathological responses rats with renal insufficiency combined with crush injury. The results were compared with those of the normal CS model group. Results : Our experiments confirm the stability of the crush injury platform. We defined the standardized conditions for modeling and successfully established rats CS model in bulk. After 12 h of compression, only 40% of the rats in the CS group survived for 24 h. Systemically, there was clear evidence of insufficient perfusion, reflecting the progression of CS from localized to generalized. The injured limbs displayed swelling, localized perfusion deficits, and severe pathological alterations. Significant changes were observed in blood biochemical markers: aspartate transaminase, lactate dehydrogenase, K+, creatine kinase, creatinine, and blood urea nitrogen levels rose rapidly after decompression and were significantly higher than the sham group. The kidney demonstrated characteristic pathological changes consistent with established CS diagnostic criteria. Although the UNx-CS rat model did not exhibit significant biochemical differences and pathological scores when compared with the standard CS model, it did yield intriguing results with regard to kidney morphology. The UNx-CS group manifested a higher incidence of cortical and medullary protein casts compared with the NC-CS group. Conclusion: We developed and iteratively refined a novel digital platform, addressing the multiple uncontrollable variables that plagued prior models. This study validated the stability of the platform, defined the standardized conditions for modeling and successfully established the CS model with good repeatability in bulk. In addition, our innovative approach to model a clinically challenging scenario, the UNx-CS rat model. This offers an opportunity to delve deeper into understanding the combined effects of preexisting renal compromise and traumatic injury. In summary, the development of a standardized, reproducible CS model in rats represents a significant milestone in the study of Crush syndrome. This study is of paramount significance as it advances the standardization of the CS model, laying a solid foundation for subsequent studies in related domains, especially in CS-AKI.

Naringin attenuates oxaliplatin-induced nephrotoxicity and hepatotoxicity: A molecular, biochemical, and histopathological approach in a rat model

Oxaliplatin (OXL) is a significant therapy agent for the worldwide increase in cancer cases. Naringin (4',5,7-trihydroxy flavonon 7-rhamnoglucoside, NRG) has a wide range of biological and pharmacological activities, including antioxidant and anti-inflammatory potentials. This research aimed to investigate NRG activity in OXL-induced hepatorenal toxicity. Accordingly, OXL (4 mg/kg b.w.) in 5% glucose was injected intraperitoneally on the first, second, fifth, and sixth days, and NRG (50 and 100 mg/kg b.w.) was given orally 30 min before to treatment. Biochemical, genetic, and histological methods were utilized to investigate the function tests, oxidant/antioxidant status, inflammation, apoptosis, and endoplasmic reticulum (ER) stress pathways in kidney and liver tissues. Administration of NRG demonstrated an antioxidant effect by increasing the activities of OXL-induced reduced antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and decreasing the elevated lipid peroxidation parameter malondialdehyde levels. Nuclear factor-κB, tumor necrosis factor-α, interleukin-1β, and inducible nitric oxide synthase levels increased in OXL administered groups but reduced in NRG-treated groups. In the OXL-administered groups, NRG reduced the apoptosis-inducing factors Caspase-3 and B-cell lymphoma 2 (Bcl-2)-associated X protein levels, while elevating the antiapoptotic factor Bcl-2 levels. OXL triggered prolonged ER stress by increasing the levels of ER stress parameters activating transcription factor 6, protein kinase R-like ER kinase, inositol-requiring enzyme 1α, and glucose-regulated protein 78. Therefore, with the NRG administration, this activity was reduced and the ER stress level decreased. Taken together, it was found that OXL induced toxicity by increasing the levels of urea and creatinine, alanine transaminase, aspartate aminotransferase, and alkaline phosphatase activities, inflammation, apoptosis, ER stress, and oxidants in the liver and kidney tissue, and NRG had a protective effect by reversing the deterioration in these pathways.

The AKI-to-CKD Transition: The Role of Uremic Toxins

After acute kidney injury (AKI), renal function continues to deteriorate in some patients. In a pro-inflammatory and profibrotic environment, the proximal tubules are subject to maladaptive repair. In the AKI-to-CKD transition, impaired recovery from AKI reduces tubular and glomerular filtration and leads to chronic kidney disease (CKD). Reduced kidney secretion capacity is characterized by the plasma accumulation of biologically active molecules, referred to as uremic toxins (UTs). These toxins have a role in the development of neurological, cardiovascular, bone, and renal complications of CKD. However, UTs might also cause CKD as well as be the consequence. Recent studies have shown that these molecules accumulate early in AKI and contribute to the establishment of this pro-inflammatory and profibrotic environment in the kidney. The objective of the present work was to review the mechanisms of UT toxicity that potentially contribute to the AKI-to-CKD transition in each renal compartment.

Inhibition of TMEM16A improves cisplatin-induced acute kidney injury via preventing DRP1-mediated mitochondrial fission

Acute kidney injury (AKI) is associated with high morbidity and mortality. Our previous study has demonstrated that TMEM16A, a Ca2+-activated chloride channel, contributes to renal fibrosis progression in chronic kidney disease. However, whether TMEM16A is involved in AKI is still unknown. In this study, we established cisplatin AKI mice model and found that TMEM16A expression was upregulated in the injured kidney. In vivo knockdown of TMEM16A effectively prevented cisplatin-induced tubular cell apoptosis, inflammation and kidney function loss. Western blot and transmission electron microscopy (TEM) revealed that TMEM16A knockdown inhibited Drp1 translocation from the cytoplasm to mitochondria and prevented mitochondrial fission in tubular cells. Consistently, in cultured HK2 cells, knockdown or inhibition of TMEM16A by shRNA or its specific inhibitor suppressed cisplatin-induced mitochondrial fission and its associated energy dysfunction, ROS accumulation, and cell apoptosis via inhibiting Drp1 activation. Further investigation showed that genetic knockdown or pharmacological inhibition of TMEM16A inhibited cisplatin-induced Drp1 Ser-616 site phosphorylation through ERK1/2 signaling pathway, whereas overexpression of TMEM16A promoted this effect. Treatment with Drp1 or ERK1/2 inhibitor could efficiently prevent cisplatin-induced mitochondrial fission. Collectively, our data suggest that TMEM16A inhibition alleviated cisplatin-induced AKI by preventing tubular cell mitochondrial fission through the ERK1/2 / Drp1 pathway. Inhibition of TMEM16A may be a novel therapeutic strategy for AKI.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Dexpanthenol protects against lipopolysaccharide-induced acute kidney injury by restoring aquaporin-2 levels via regulation of the silent information regulator 1 signaling pathway

BACKGROUND

Acute kidney injury (AKI) is a serious pathology that causes dysfunction in concentrating urine due to kidney damage, resulting in blood pressure dysregulation and increased levels of toxic metabolites. Dexpanthenol (DEX), a pantothenic acid analog, exhibits anti-inflammatory and anti-apoptotic properties in various tissues. This study investigated the protective effects of DEX against systemic inflammation-induced AKI.

METHODS

Thirty-two female rats were randomly assigned to the control, lipopolysaccharide (LPS), LPS+DEX, and DEX groups. LPS (5 mg/kg, single dose on the third day, 6 h before sacrifice) and DEX (500 mg/kg/d for 3 d) were administered intraperitoneally. After sacrifice, blood samples and kidney tissues were collected. Hematoxylin and eosin, caspase-3 (Cas-3), and tumor necrosis factor alpha (TNF-α) staining were performed on the kidney tissues. The total oxidant status (TOS) and total antioxidant status were measured using spectrophotometric methods. Aquaporin-2 (AQP-2), silent information regulator 1 (SIRT1), and interleukin-6 (IL-6) were detected using quantitative reverse transcription-polymerase chain reaction analysis.

RESULTS

Histopathological analysis revealed that DEX treatment ameliorated histopathological changes. In the LPS group, an increase in the blood urea nitrogen, creatinine, urea, IL-6, Cas-3, TNF-α, and TOS levels and oxidative stress index was observed compared with the control group, whereas AQP-2 and SIRT1 levels decreased. DEX treatment reversed these effects.

CONCLUSIONS

DEX was found to effectively prevent inflammation, oxidative stress, and apoptosis in the kidneys via the SIRT1 signaling pathway. These protective properties suggest DEX's potential as a therapeutic agent for the treatment of kidney pathologies.

Role of extracellular vesicles in pathogenesis and therapy of renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (RIRI) is a complex disorder characterized by both intrinsic damage to renal tubular epithelial cells and extrinsic inflammation mediated by cytokines and immune cells. Unfortunately, there is no cure for this devastating condition. Extracellular vesicles (EVs) are nanosized membrane-bound vesicles secreted by various cell types that can transfer bioactive molecules to target cells and modulate their function. EVs have emerged as promising candidates for cell-free therapy of RIRI, owing to their ability to cross biological barriers and deliver protective signals to injured renal cells. In this review, we provide an overview of EVs, focusing on their functional role in RIRI and the signaling messengers responsible for EV-mediated crosstalk between various cell types in renal tissue. We also discuss the renoprotective role of EVs and their use as therapeutic agents for RIRI, highlighting the advantages and challenges encountered in the therapeutic application of EVs in renal disease.

The early diagnosis and pathogenic mechanisms of sepsis-related acute kidney injury

Sepsis is a syndrome caused by an imbalance in the inflammatory response of the body caused by an infection that leads to organ dysfunction, with the kidney being one of the most commonly affected organs. Sepsis-related acute kidney injury (SAKI) is strongly linked to increased mortality and poor clinical outcomes. Early diagnosis and treatment can significantly reduce patient mortality. On the other hand, the pathogenesis of SAKI is not fully understood, and early diagnosis of SAKI is a clinical challenge. Therefore, the current review describes biomarkers of acute kidney injury in sepsis and discusses the various pathogenic mechanisms involved in the progression of acute kidney injury in sepsis to develop new clinical treatment avenues.

Thiopental sodium attenuates hypoxia/reoxygenation-induced injury in osteoblasts by modulating AKT signaling

Thiopental sodium (TPTS) is a barbiturate general anesthetic, while its effects on hypoxia/reoxygenation (H/R)-induced injury are still unclear. This study aimed to investigate whether TPTS exerts protective effects against the H/R-induced osteoblast cell injury and explore the underlying mechanisms. Osteoblast cell injury model was induced by the H/R condition, which was treated with or without TPTS. Cell viability and lactate dehydrogenase (LDH) release were determined by the corresponding commercial kits. The levels of oxidative stress were determined in the experimental groups. Cell apoptosis and Caspase-3 activities were determined by propidium iodide staining and substrate-based assay, respectively. Western blotting and qRT-PCR were performed to measure the mRNA and protein levels, respectively. Treatment with TPTS was able to increase cell viability and reduce LDH release in H/R-induced osteoblasts. Additionally, TPTS regulated oxidative stress in H/R-induced osteoblasts by suppressing malondialdehyde (MDA) and reactive oxygen species (ROS) as well as boosting superoxide dismutase (SOD). TPTS was able to suppress cell apoptosis by suppressing Caspase-3 activity and cleavage. TPTS exerted protective effects against cell injury and apoptosis induced by the H/R conditions, which were associated with its regulation of Akt signaling. Moreover, TPTS induced osteoblast differentiation under the H/R condition. In summary, TPTS attenuates H/R-induced injury in osteoblasts by regulating AKT signaling.

The potential renoprotective effect of Raloxifene in renal ischemia-reperfusion injury in a male rat model

Renal ischemia-reperfusion injury is caused by a temporary reduction in oxygen-carrying blood flow to the kidney, followed by reperfusion. During ischemia, kidney tissue damage induces overproduction of reactive oxygen species, which produces oxidative stress. The blood flow restoration during the reperfusion period causes further production of reactive oxygen species that ends with apoptosis and cell death. This study aimed to investigate the potential renoprotective effects of Raloxifene on bilateral renal ischemia-reperfusion injury in rats by looking into kidney function biomarkers, urea and creatinine, inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). Additionally, antioxidant markers such as total antioxidant capacity (TAC) and the pro-apoptotic marker caspase-3 were assessed. Histopathological scores were also employed for evaluation. Our experimental design involved 20 rats divided into four groups: the sham group underwent median laparotomy without ischemia induction, the control group experienced bilateral renal ischemia for 30 minutes followed by 2 hours of reperfusion, the vehicle group received pretreatment with a mixture of corn oil and dimethyl sulfoxide (DMSO) before ischemia induction, and the Raloxifene-treated group was administered Raloxifene at a dose of 10 mg/kg before ischemia induction, followed by ischemia-reperfusion. Urea and creatinine, TNF-α, IL-1β, and caspase-3 in the Raloxifene group were significantly lower compared to the control and vehicle groups. On the other hand, TAC levels in the Raloxifene group were significantly higher than in the control and vehicle groups. This study concluded that Raloxifene had a renoprotective impact via multiple actions as an anti-inflammatory, anti-apoptotic, and antioxidant agent.

Apoptotic exosome-like vesicles transfer specific and functional mRNAs to endothelial cells by phosphatidylserine-dependent macropinocytosis

Apoptosis of endothelial cells prompts the release of apoptotic exosome-like vesicles (ApoExos), subtype extracellular vesicles secreted by apoptotic cells after caspase-3 activation. ApoExos are different from both apoptotic bodies and classical exosomes in their protein and nucleic acid contents and functions. In contrast to classical apoptotic bodies, ApoExos induce immunogenic responses that can be maladaptive when not tightly regulated. In the present study, we elucidated the mechanisms by which ApoExos are internalized by endothelial cells, which leads to shared specific and functional mRNAs of importance to endothelial function. Using flow cytometry and confocal microscopy, we revealed that ApoExos were actively internalized by endothelial cells. SiRNA-induced inhibition of classical endocytosis pathways with pharmacological inhibitors showed that ApoExos were internalized via phosphatidylserine-dependent macropinocytosis independently of classical endocytosis pathways. An electron microscopy analysis revealed that ApoExos increased the macropinocytosis rate in endothelial cells, setting in motion a positive feedback loop that increased the amount of internalized ApoExos. Deep sequencing of total RNA revealed that ApoExos possessed a unique protein-coding RNA profile, with PCSK5 being the most abundant mRNA. Internalization of ApoExos by cells led to the transfer of this RNA content from the ApoExos to cells. Specifically, PCSK5 mRNA was transferred to cells that had taken up ApoExos, and these cells subsequently expressed PCSK5. Collectively, our findings suggest that macropinocytosis is an effective entry pathway for the delivery of RNAs carried by ApoExos and that these RNAs are functionally expressed by the endothelial cells that internalize them. As ApoExos express a specific mRNA signature, these results suggest new avenues to understand how ApoExos produced at sites of vascular injury impact vascular function.

Dynamic cellular changes in acute kidney injury caused by different ischemia time

Ischemia reperfusion injury (IRI), often related to surgical procedures, is one of the important causes of acute kidney injury (AKI). To decipher the dynamic process of AKI caused by IRI (with prolonged ischemia phase), we performed single-cell RNA sequencing (scRNA-seq) of clinically relevant IRI murine model with different ischemic intervals. We discovered that Slc5a2^hi proximal tubular cells were susceptible to AKI and highly expressed neutral amino acid transporter gene Slc6a19, which was dramatically decreased over the time course. With the usage of mass spectrometry-based metabolomic analysis, we detected that the level of neutral amino acid isoleucine dropped off in AKI mouse plasma metabolites. And the reduction of plasma isoleucine was also verified in patients with cardiac surgery-associated acute kidney injury (CSA-AKI). The findings advanced the understanding of dynamic process of AKI and introduced reduction of isoleucine as a potential biomarker for CSA-AKI.

Analysis of the potential biological mechanisms of diosmin against renal fibrosis based on network pharmacology and molecular docking approach

BACKGROUND

Interstitial fibrosis is involved in the progression of various chronic kidney diseases and renal failure. Diosmin is a naturally occurring flavonoid glycoside that has antioxidant, anti-inflammatory, and antifibrotic activities. However, whether diosmin protects kidneys by inhibiting renal fibrosis is unknown.

METHODS

The molecular formula of diosmin was obtained, targets related to diosmin and renal fibrosis were screened, and interactions among overlapping genes were analyzed. Overlapping genes were used for gene function and KEGG pathway enrichment analysis. TGF-β1 was used to induce fibrosis in HK-2 cells, and diosmin treatment was administered. The expression levels of relevant mRNA were then detected.

RESULTS

Network analysis identified 295 potential target genes for diosmin, 6828 for renal fibrosis, and 150 hub genes. Protein-protein interaction network results showed that CASP3, SRC, ANXA5, MMP9, HSP90AA1, IGF1, RHOA, ESR1, EGFR, and CDC42 were identified as key therapeutic targets. GO analysis revealed that these key targets may be involved in the negative regulation of apoptosis and protein phosphorylation. KEGG indicated that pathways in cancer, MAPK signaling pathway, Ras signaling pathway, PI3K-Akt signaling pathway, and HIF-1 signaling pathway were key pathways for renal fibrosis treatment. Molecular docking results showed that CASP3, ANXA5, MMP9, and HSP90AA1 stably bind to diosmin. Diosmin treatment inhibited the protein and mRNA levels of CASP3, MMP9, ANXA5, and HSP90AA1. Network pharmacology analysis and experimental results suggest that diosmin ameliorates renal fibrosis by decreasing the expression of CASP3, ANXA5, MMP9, and HSP90AA1.

CONCLUSIONS

Diosmin has a potential multi-component, multi-target, and multi-pathway molecular mechanism of action in the treatment of renal fibrosis. CASP3, MMP9, ANXA5, and HSP90AA1 might be the most important direct targets of diosmin.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Regulated cell death pathways in kidney disease

Disorders of cell number that result from an imbalance between the death of parenchymal cells and the proliferation or recruitment of maladaptive cells contributes to the pathogenesis of kidney disease. Acute kidney injury can result from an acute loss of kidney epithelial cells. In chronic kidney disease, loss of kidney epithelial cells leads to glomerulosclerosis and tubular atrophy, whereas interstitial inflammation and fibrosis result from an excess of leukocytes and myofibroblasts. Other conditions, such as acquired cystic disease and kidney cancer, are characterized by excess numbers of cyst wall and malignant cells, respectively. Cell death modalities act to clear unwanted cells, but disproportionate responses can contribute to the detrimental loss of kidney cells. Indeed, pathways of regulated cell death - including apoptosis and necrosis - have emerged as central events in the pathogenesis of various kidney diseases that may be amenable to therapeutic intervention. Modes of regulated necrosis, such as ferroptosis, necroptosis and pyroptosis may cause kidney injury directly or through the recruitment of immune cells and stimulation of inflammatory responses. Importantly, multiple layers of interconnections exist between different modalities of regulated cell death, including shared triggers, molecular components and protective mechanisms.

Kidney fibrosis: from mechanisms to therapeutic medicines

Chronic kidney disease (CKD) is estimated to affect 10-14% of global population. Kidney fibrosis, characterized by excessive extracellular matrix deposition leading to scarring, is a hallmark manifestation in different progressive CKD; However, at present no antifibrotic therapies against CKD exist. Kidney fibrosis is identified by tubule atrophy, interstitial chronic inflammation and fibrogenesis, glomerulosclerosis, and vascular rarefaction. Fibrotic niche, where organ fibrosis initiates, is a complex interplay between injured parenchyma (like tubular cells) and multiple non-parenchymal cell lineages (immune and mesenchymal cells) located spatially within scarring areas. Although the mechanisms of kidney fibrosis are complicated due to the kinds of cells involved, with the help of single-cell technology, many key questions have been explored, such as what kind of renal tubules are profibrotic, where myofibroblasts originate, which immune cells are involved, and how cells communicate with each other. In addition, genetics and epigenetics are deeper mechanisms that regulate kidney fibrosis. And the reversible nature of epigenetic changes including DNA methylation, RNA interference, and chromatin remodeling, gives an opportunity to stop or reverse kidney fibrosis by therapeutic strategies. More marketed (e.g., RAS blockage, SGLT2 inhibitors) have been developed to delay CKD progression in recent years. Furthermore, a better understanding of renal fibrosis is also favored to discover biomarkers of fibrotic injury. In the review, we update recent advances in the mechanism of renal fibrosis and summarize novel biomarkers and antifibrotic treatment for CKD.

Human umbilical cord mesenchymal stem cell exosome-derived miR-874-3p targeting RIPK1/PGAM5 attenuates kidney tubular epithelial cell damage

BACKGROUND

Kidney insults due to various pathogenic factors, such as trauma, infection, and inflammation, can cause tubular epithelial cell injury and death, leading to acute kidney injury and the transformation of acute kidney injury to chronic kidney disease. There is no definitive treatment available. In previous studies, human umbilical cord mesenchymal stem cells have been shown to promote kidney injury. In this preclinical study, we investigate the role and mechanism of human umbilical cord mesenchymal stem cell exosomes (HucMSC-Exos) on the repair of renal tubular epithelial cells after injury.

METHODS

C57BL/6 mice underwent unilateral ureteral obstruction, and epithelial cell injury was induced in HK-2 cells by cisplatin. HucMSC-Exos were assessed in vivo and in vitro. The extent of renal cell injury, activation of necroptosis pathway, and mitochondrial quality-control-related factors were determined in different groups. We also analyzed the possible regulatory effector molecules in HucMSC-Exos by transcriptomics.

RESULTS

HucMSC-Exo inhibited necroptosis after renal tubular epithelial cell injury and promoted the dephosphorylation of the S637 site of the Drp1 gene by reducing the expression of PGAM5. This subsequently inhibited mitochondrial fission and maintained mitochondrial functional homeostasis, mitigating renal injury and promoting repair. In addition, HucMSC-Exo displayed a regulatory role by targeting RIPK1 through miR-874-3p.

CONCLUSION

The collective findings of the present study demonstrate that HucMSC-Exos can regulate necroptosis through miR-874-3p to attenuate renal tubular epithelial cell injury and enhance repair, providing new therapeutic modalities and ideas for the treatment of AKI and the process of AKI to CKD transformation to mitigate renal damage.

Succinate-SUCNR1 induces renal tubular cell apoptosis

Succinate has long been known to be only an intermediate product of the tricarboxylic acid cycle until identified as a natural ligand for SUCNR1 in 2004. SUCNR1 is widely expressed throughout the body, especially in the kidney. Abnormally elevated succinate is associated with many diseases, including obesity, type 2 diabetes, nonalcoholic fatty liver disease, and ischemia injury, but it is not known whether succinate can cause kidney damage. This study showed that succinate induced apparent renal injury after treatment for 12 wk, characterized by a reduction in 24 h urine and the significant detachment of the brush border of proximal tubular epithelial cells, tubular dilation, cast formation, and vacuolar degeneration of tubular cells in succinate-treated mice. Besides, succinate caused tubular epithelial cell apoptosis in kidneys and HK-2 cells. Mechanistically, succinate triggered cell apoptosis via SUCNR1 activation. In addition, succinate upregulated ERK by binding to SUCNR1, and inhibition of ERK using PD98059 abolished the proapoptotic effects of succinate in HK-2 cells. In summary, our study provides the first evidence that succinate acts as a risk factor and contributes to renal injury, and further research is required to discern the pathological effects of succinate on renal functions.

AFM negatively regulates the infiltration of monocytes to mediate sepsis-associated acute kidney injury

Background

Sepsis is organ dysfunction due to the host's deleterious response to infection, and the kidneys are one of the organs damaged in common sepsis. Sepsis-associated acute kidney injury (SA-AKI) increases the mortality in patients with sepsis. Although a substantial volume of research has improved the prevention and treatment of the disease, SA-SKI is still a significant clinical concern.

Purpose

Aimed to use weighted gene co-expression network analysis (WGCNA) and immunoinfiltration analysis to study SA-AKI-related diagnostic markers and potential therapeutic targets.

Methods

Immunoinfiltration analysis was performed on SA-AKI expression datasets from the Gene Expression Synthesis (GEO) database. A weighted gene co-expression network analysis (WGCNA) analysis was performed on immune invasion scores as trait data, and modules associated with immune cells of interest were identified as hub modules. Screening hub geneset in the hub module using protein-protein interaction (PPI) network analysis. The hub gene was identified as a target by intersecting with significantly different genes screened by differential expression analysis and validated using two external datasets. Finally, the correlation between the target gene, SA-AKI, and immune cells was verified experimentally.

Results

Green modules associated with monocytes were identified using WGCNA and immune infiltration analysis. Differential expression analysis and PPI network analysis identified two hub genes (AFM and GSTA1). Further validation using additional AKI datasets GSE30718 and GSE44925 showed that AFM was significantly downregulated in AKI samples and correlated with the development of AKI. The correlation analysis of hub genes and immune cells showed that AFM was significantly associated with monocyte infiltration and hence, selected as a critical gene. In addition, Gene single-enrichment analysis (GSEA) and PPI analyses results showed that AFM was significantly related to the occurrence and development of SA-AKI.

Conclusions

AFM is inversely correlated with the recruitment of monocytes and the release of various inflammatory factors in the kidneys of AKI. AFM can be a potential biomarker and therapeutic target for monocyte infiltration in sepsis-related AKI.

Aluminum exposure induces nephrotoxicity via fibrosis and apoptosis through the TGF-β1/Smads pathway in vivo and in vitro

Aluminum (Al), the most common element in nature, can enter the body through various routes. Unfortunately, excessive accumulation of Al in the body can cause chronic toxicity. In this study, rats were randomly allocated to 4 groups and intraperitoneally injected with AlCl₃ solution at 0, 5, 10, and 20 mg/(kg·d), respectively, for 4 weeks. The kidney function of rats and Al contents in the kidney were measured, and the pathological structural changes and apoptosis of the kidney were observed. Meanwhile, the expression of fibrosis- and apoptosis-related proteins was detected with western blot. For the in vitro assay, HK-2 cells were used to construct a model to evaluate the effects of Al exposure on cell viability, cell apoptosis, and the expression of fibrosis- and apoptosis-related proteins. Additionally, the TGF-β1/Smads pathway was also altered in HK-2 cells, followed by the measurement of changes in apoptosis and fibrosis-related proteins. The results revealed that Al could accumulate in kidney tissues, then leading to histopathological changes and kidney function impairment, promoting renal tubular cell apoptosis and renal collagen fiber deposition, and also elevating the expression of TGF-β1/Smads pathway-related proteins. In vitro experiments also exhibited that Al exposure increased apoptosis and the expression of fibrosis-related factors in HK-2 cells, accompanied by activation of the TGF-β1/Smads pathway. Further modulation of the TGF-β1/Smads pathway manifested that activation of the TGF-β1/Smads pathway facilitated Al-induced apoptosis and fibrosis-related factor expression, while inhibition of the pathway negated this effect of Al. In conclusion, the findings of the present study illustrate that Al exposure damages kidney function and facilitate apoptosis and kidney fibrosis, which may be achieved through the activation of the TGF-β1/Smads pathway. This study provides a new theoretical basis for the study of nephrotoxicity induced by excessive Al exposure.

Contrast-enhanced ultrasound in evaluating the severity of acute kidney injury: An animal experimental study

PURPOSE

Early assessment of the severity of acute kidney injury (AKI) is critical to the prognosis of patients. Renal microcirculation hemodynamic changes and inflammatory response are the essential links of AKI induced by ischemia-reperfusion injury (IRI). This study aims to explore the value of contrast-enhanced ultrasound (CEUS) based on vascular cell adhesion molecule-1 (VCAM-1) targeted microbubbles (TM) in evaluating the renal microcirculation hemodynamics and inflammatory response of different severity of AKI.

METHODS

Eighteen male C57BL/6J mice were randomly divided into three groups (n = 6): sham operation (sham) group, mild IRI-AKI (m-AKI) group, and severe IRI-AKI (s-AKI) group. CEUS based on VCAM-1 TM was used to evaluate renal microcirculation perfusion and inflammatory response. Pearson's correlation was used to analyze the correlation between ultrasonic variables and pro-inflammatory factors.

RESULTS

Compared with the sham group, AUC in m-AKI and s-AKI groups was significantly decreased, and s-AKI group was lower than m-AKI group (P < 0.05). NID of m-AKI and s-AKI groups was significantly higher than that of the sham group, and s-AKI group was higher than that of m-AKI group (P < 0.05). There was a linear positive correlation between NID and VCAM-1 protein expression (r = 0.7384, P < 0.05). NID and AUC were correlated with TNF-α and IL-6 levels (P < 0.05). Compared with early AKI biomarkers, CEUS based on VCAM-1 TM has higher sensitivity in evaluating the severity of AKI.

CONCLUSIONS

CEUS based on VCAM-1 TM can evaluate renal microcirculation perfusion and inflammatory response in mild and severe AKI, which may provide helpful information for assessing the severity of AKI.

Effect of fetuin-A on adenine-induced chronic kidney disease model in male rats

Objectives

This study aimed to investigate the possible effects of fetuin-A on an adenine-induced chronic kidney disease (CKD) model in male rats.

Materials and Methods

Rats were divided into three groups: group A included rats fed a normal diet; group B included rats fed a normal diet with 220 mg/kg adenine daily for 21 days; group C included rats fed a normal diet with 220 mg/kg adenine daily for 21 days and intraperitoneally administered with 5 mg\kg fetuin-A every other day for 2 weeks. Serum samples were assayed for serum creatinine, urea, sodium, potassium, calcium, phosphorus, tumor necrosis factor (TNF), interleukin-6 (IL-6), and estimated glomerular filtration rate (eGFR), and immunohistochemical staining was performed.

Results

Group B showed a significant increase in serum creatinine, urea, phosphorus, potassium, TNF, and IL-6 and a significant decrease in serum sodium, calcium, and eGFR compared with group A. Regarding immunohistochemistry, group B showed increased apoptosis. In group C, fetuin-A reduced the urea, creatinine, and phosphorus levels, and in group C, fetuin-A decreased inflammation and apoptosis by reduction of caspase-3 staining.

Conclusion

Fetuin-A improved kidney function in CKD due to its anti-inflammatory and anti-fibrotic role.

THE POTENTIAL RENOPROTECTIVE EFFECT OF TILIANIN IN RENAL ISCHEMIA REPERFUSION INJURY IN MALE RAT MODEL

OBJECTIVE

The aim: To determine whether Tilianin (TIL) may have Nephroprotective effects on bilateral renal IRI in rats by analyzing kidney function biomarkers U and Cr, inflammatory cytokines like TNF α and IL-1β, antioxidant marker total anti-oxidant Capacity (TAC), anti-apoptotic markers caspase-3, and histopathological scores.

PATIENTS AND METHODS

Materials and methods: 20 rats divided into even 4 groups as: Sham group: Rats underwent median laparotomies without having their ischemia induced. Control group: Rats had bilateral renal ischemia for 30 minutes, followed by 2 hours of reperfusion. Vehicle group: 30 minutes prior to the onset of ischemia, rats were given a pretreatment of corn oil and DMSO. Tilianin treated group: Rats administered Tilianin 5 mg/kg for 30 min prior to ischemia induction, then IRI.

RESULTS

Results: The study found that the serum levels of TNF, IL-1, caspase-3, urea and creatinine, as well as TNF and creatinine in the Tilianin group were significantly lower than those of the control and vehicle groups. On the other hand, it revealed that TAC levels are remarkably higher in the Tilianin group than they are in the control and vehicle groups.

CONCLUSION

Conclusions: This study concluded that Tilianin have a Nephroprotective effect via multiple impacts as anti-inflammatory, anti-apoptotic, and anti-oxidant agents.

Hypothermic Perfusion Modifies the Association Between Anti-LG3 Antibodies and Delayed Graft Function in Kidney Recipients

We previously reported associations between autoantibodies to the LG3 fragment of perlecan, anti-LG3, and a higher risk of delayed graft function (DGF) in kidney transplant recipients. Here, we aimed to determine whether some factors that modulate ischemia-reperfusion injury (IRI) can modify this association. We performed a retrospective cohort study in kidney transplant recipients in 2 university-affiliated centers. In 687 patients, we show that high pre-transplant anti-LG3 are associated with DGF when the kidney is transported on ice (odds ratio (OR): 1.75, 95% confidence interval 1.02-3.00), but not when placed on hypothermic perfusion pump (OR: 0.78, 95% CI 0.43-1.37). In patients with DGF, high pre-transplant anti-LG3 are associated with a higher risk of graft failure (subdistribution hazard ratio (SHR): 4.07, 95% CI: 1.80, 9.22), while this was not the case in patients with immediate graft function (SHR: 0.50, 95% CI 0.19, 1.29). High anti-LG3 levels are associated with a higher risk of DGF in kidneys exposed to cold storage, but not when hypothermic pump perfusion is used. High anti-LG3 are also associated with a higher risk of graft failure in patients who experience DGF, a clinical manifestation of severe IRI.

Lasmiditan promotes recovery from acute kidney injury through induction of mitochondrial biogenesis

Acute kidney injury (AKI) involves rapid loss of renal function and occurs in 8-16% of hospitalized patients. AKI can be induced by drugs, sepsis, and ischemia-reperfusion (I/R). Hallmarks of AKI include mitochondrial and microvasculature dysfunction as well as renal tubular injury. There is currently no available therapeutic for AKI. Previously, our group identified that serotonin (5-HT)1F receptor agonism with lasmiditan accelerated endothelial cell recovery and induced mitochondrial biogenesis (MB) in vitro. We hypothesized that lasmiditan, a Federal Drug Administration-approved drug, would induce MB and improve microvascular and renal function in a mouse model of AKI. Male mice were subjected to renal I/R and treated with lasmiditan (0.3 mg/kg) or vehicle beginning 24 h after injury and then daily until euthanasia at 6 or 12 days. Serum creatinine was measured to estimate glomerular filtration rate. The renal cortex was assessed for mitochondrial density, vascular permeability and integrity, tubular damage, and interstitial fibrosis. Lasmiditan increased mitochondrial number (1.4-fold) in renal cortices. At 6 days, serum creatinine decreased 41% in the I/R group and 72% with lasmiditan. At 6 or 12 days, kidney injury molecule-1 increased in the I/R group and decreased 50% with lasmiditan. At 12 days, interstitial fibrosis decreased with lasmiditan by 50% and collagen type 1 by 38%. Evan's blue dye leakage increased 2.5-fold in the I/R group and was restored with lasmiditan. The tight junction proteins zonula occludens-1, claudin-2, and claudin-5 decreased in the I/R group and recovered with lasmiditan. At 6 or 12 days, peroxisome proliferator-activated receptor-γ coactivator-1α and electron transport chain complexes increased only with lasmiditan. In conclusion, lasmiditan treatment beginning AKI induces MB, attenuated vascular and tubular injury, decreased interstitial fibrosis, and lowered serum creatinine. Given that lasmiditan is a Federal Drug Administration-approved drug, these preclinical data support repurposing lasmiditan as a therapeutic for AKI.NEW & NOTEWORTHY AKI pathology involves a rapid decline in kidney function and occurs in 8-16% of hospitalized patients. There is currently no therapeutic for AKI. AKI results in mitochondria dysfunction, microvasculature injury, and loss of renal tubular function. In an I/R-induced AKI mouse model, treatment with the FDA-approved 5-HT1F receptor-selective agonist lasmiditan induced mitochondrial biogenesis, improved vascular integrity, reduced fibrosis, and reduced proximal tubule damage. These data support repurposing lasmiditan for the treatment of AKI.

The multifaceted role of kidney tubule mitochondrial dysfunction in kidney disease development

More than 800 million people suffer from kidney disease. Genetic studies and follow-up animal models and cell biological experiments indicate the key role of proximal tubule metabolism. Kidneys have one of the highest mitochondrial densities. Mitochondrial biogenesis, mitochondrial fusion and fission, and mitochondrial recycling, such as mitophagy are critical for proper mitochondrial function. Mitochondrial dysfunction can lead to an energetic crisis, orchestrate different types of cell death (apoptosis, necroptosis, pyroptosis, and ferroptosis), and influence cellular calcium levels and redox status. Collectively, mitochondrial defects in renal tubules contribute to epithelial atrophy, inflammation, or cell death, orchestrating kidney disease development.

Experimental Study on Danggui Shaoyao San Improving Renal Fibrosis by Promoting Autophagy

Renal fibrosis could lead to chronic kidney disease (CKD) developing into the end-stage with its pathological manifestation is the deposition of extracellular matrix (ECM). Danggui Shaoyao San (DSS) is one of the widely used herbal formulas in ancient China, which has been proven to have efficacy in the treatment of CKD. The experiment employed TGF-β1 to stimulate the NRK-52E cells to establish a renal fibrosis model. With rapamycin (RAPA) used as the positive control, we detected the expression of fibronectin (FN), caspase-3, and autophagy-related proteins in the NRK-52E cells treated with DSS by Western blot and immunofluorescence assay. In order to further verify autophagy-promoting effects of DSS, we adopted 3-MA to inhibit autophagy. The experiment has found that DSS can lower the protein levels of FN and caspase-3 in the NRK-52E cells induced by TGF-β1. After TGF-β1 stimulation, the expression of LC3 II/I and Beclin 1 has decreased, and the protein levels of mTOR and p62 have increased. Consistent with rapamycin, DSS has significantly reduced these effects of TGF-β1. It has also been found that DSS can increase the expression of LC3 II/I and Beclin 1 proteins and can reduce the level of mTOR in cells treated with 3-MA, suggesting that DSS can promote autophagy. In conclusion, DSS has been proved to reduce the apoptosis and fibrosis of NRK-52E cells induced by TGF-β1, which may be achieved by promoting autophagy.

DUSP2-mediated inhibition of tubular epithelial cell pyroptosis confers nephroprotection in acute kidney injury

Rationale: Acute kidney injury (AKI) is pathologically characterized by renal tubular epithelial cell (RTEC) death and interstitial inflammation, while their pathogenesis remains incompletely understood. Dual-specificity phosphatase 2 (DUSP2) recently emerges as a crucial regulator of cell death and inflammation in a wide range of diseases, but its roles in renal pathophysiology are largely unknown. Methods: The expression of DUSP2 in the kidney was characterized by histological analysis in renal tissues from patients and mice with AKI. The role and mechanism of DUSP2-mediated inhibition of tubular epithelial cell pyroptosis in AKI were evaluated both in vivo and in vitro, and confirmed in RTEC-specific deletion of DUSP2 mice. Results: Here, we show that DUSP2 is enriched in RTECs in the renal tissue of both human and mouse and mainly positions in the nucleus. Further, we reveal that loss-of-DUSP2 in RTECs not only is a common feature of human and murine AKI but also positively contributes to AKI pathogenesis. Especially, RTEC-specific deletion of DUSP2 sensitizes mice to AKI by promoting RTEC pyroptosis and the resultant interstitial inflammation. Mechanistic studies show that gasdermin D (GSDMD), which mediates RTEC pyroptosis, is identified as a transcriptional target of activated STAT1 during AKI, whereas DUSP2 as a nuclear phosphatase deactivates STAT1 to restrict GSDMD-mediated RTEC pyroptosis. Importantly, DUSP2 overexpression in RTECs via adeno-associated virus-mediated gene transfer significantly ameliorates AKI. Conclusion: Our findings demonstrate a hitherto unrecognized role of DUSP2-STAT1 axis in regulating RTEC pyroptosis in AKI, highlighting that DUSP2-STAT1 axis is an attractive therapeutic target for AKI.

Chronic critical illness and post-intensive care syndrome: from pathophysiology to clinical challenges

Background

Post‐intensive care syndrome (PICS) encompasses physical, cognition, and mental impairments persisting after intensive care unit (ICU) discharge. Ultimately it significantly impacts the long‐term prognosis, both in functional outcomes and survival. Thus, survivors often develop permanent disabilities, consume a lot of healthcare resources, and may experience prolonged suffering. This review aims to present the multiple facets of the PICS, decipher its underlying mechanisms, and highlight future research directions.

Main text

This review abridges the translational data underlying the multiple facets of chronic critical illness (CCI) and PICS. We focus first on ICU-acquired weakness, a syndrome characterized by impaired contractility, muscle wasting, and persisting muscle atrophy during the recovery phase, which involves anabolic resistance, impaired capacity of regeneration, mitochondrial dysfunction, and abnormalities in calcium homeostasis. Second, we discuss the clinical relevance of post-ICU cognitive impairment and neuropsychological disability, its association with delirium during the ICU stay, and the putative role of low-grade long-lasting inflammation. Third, we describe the profound and persistent qualitative and quantitative alteration of the innate and adaptive response. Fourth, we discuss the biological mechanisms of the progression from acute to chronic kidney injury, opening the field for renoprotective strategies. Fifth, we report long-lasting pulmonary consequences of ARDS and prolonged mechanical ventilation. Finally, we discuss several specificities in children, including the influence of the child’s pre-ICU condition, development, and maturation.

Conclusions

Recent understandings of the biological substratum of the PICS’ distinct features highlight the need to rethink our patient trajectories in the long term. A better knowledge of this syndrome and precipitating factors is necessary to develop protocols and strategies to alleviate the CCI and PICS and ultimately improve patient recovery.

Decoy Receptor 3 Suppresses T-Cell Priming and Promotes Apoptosis of Effector T-Cells in Acute Cell-Mediated Rejection: The Role of Reverse Signaling

Background

Decoy receptor 3 (DcR3) belongs to the tumor necrosis factor (TNF) receptor superfamily and neutralizes TNF ligands, including FasL and TRAIL, to prevent T activation during T-cell priming. However, the cellular mechanisms underlying acute cell-mediated rejection (ACMR) remain unknown.

Methods

We generated DcR3 transgenic (Tg) mice and mice with high DcR3 expression (HDE) to study both in vivo and in vitro. FasR RNA knockdown in immortalized CD4⁺CD8⁺ T-cells was used to survey the role of DcR3 on FasR/Fas-associated protein with death domain (FADD)/caspase 8 pathway and its cross-link to TNF receptor-associated factor 1 (TNFR1)-associated death domain protein (TRADD) in suppressing TNFR1. TNF/TRADD knockout mice were used to show the importance of TNF adaptor protein.

Results

DcR3.Fc suppressed C57BL/6 female T-cell activation and transformation into CD4⁺CD69⁺, CD4⁺CD44⁺, and CD4⁺CD25⁺Foxp3⁺ when compared with isotype IgG1 and its co-treatment with FasL/TRAIL after exposing to bone marrow-derived dendritic cells (BMDCs) that carried alloantigen with male H-Y and minor antigenic determinant. Interleukin-17 and interferon-γ productions by BMDC-activated T-cells were lowered after co-treating with DcR3.Fc. DcR3.Fc induced effector T-cells (Teffs) and was susceptible to FasR-mediated apoptosis through the FADD/TRADD/caspase 8 pathway. After exposing to DcR3.Fc, TRADD was silenced, likely turning down the inflammatory response. The systemic effects of DcR3 Tg mice and HDE phenotype induced by the promoter of cytomegalovirus not only attenuated ACMR severity but also ameliorated the high serum creatinine and blood urea nitrogen levels even with high T-cell exposure frequencies. Besides this, DcR3 has minor biological effects on both MHC-matched and MHC-mismatched models.

Conclusions

High DcR3 doses protect renal tubular epithelial cells from acute T-cell attack during the T-cell priming stage via interfering with TNF ligand-mediated reverse signaling and possibly promoting Teff apoptosis through FasR upregulation. Our findings supported that the decoy receptor is involved in T-cell modulation in kidney transplant rejection.

Small molecules as modulators of regulated cell death against ischemia/reperfusion injury

Ischemia/reperfusion (IR) injury contributes to disability and mortality worldwide. Due to the complicated mechanisms and lack of proper therapeutic targets, few interventions are available that specifically target the pathogenesis of IR injury. Regulated cell death (RCD) of endothelial and parenchymal cells is recognized as the promising intervening target. Recent advances in IR injury suggest that small molecules exhibit beneficial effects on various RCD against IR injury, including apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis, and parthanatos. Here, we describe the mechanisms behind these novel promising therapeutic targets and explain the machinery powering the small molecules. These small molecules exert protection by targeting endothelial or parenchymal cells to alleviate IR injury. Therapies of the ideal combination of small molecules targeting multiple cell types have shown potent synergetic therapeutic effects, laying the foundation for novel strategies to attenuate IR injury.

Maslinic Acid Attenuates Ischemia/Reperfusion-Induced Acute Kidney Injury by Suppressing Inflammation and Apoptosis Through Inhibiting NF-κB and MAPK Signaling Pathway

Inflammation and apoptosis are the major contributors to the mechanisms of acute kidney injury (AKI) due to renal ischemia-reperfusion injury (IRI). Maslinic acid (MA), a pentacyclic triterpene acid mostly found in dietary plants, the current study was to demonstrate the renoprotective effect of MA on IRI-induced AKI, and to investigate the role of inflammation and apoptosis-related signaling pathways as a molecular mechanism. C57BL/6J mice were subjected to IRI for 72 h, and MA was daily administered by intraperitoneal injection during this period. In parallel, rat renal proximal tubule cells (NRK52E) were prophylactically treated with MA and then exposed to hydrogen peroxide (H₂O₂). MA treatment significantly inhibited the mRNA expression of interleukin (IL-1β), tumor necrosis factor-α (TGF-α), monocyte chemoattractant protein-1 (MCP-1), and intercellular adhesion molecule-1(ICAM-1). Also, MA reduced the expression of Bax/Bcl2 ratio and cleaved caspase-3. In NRK52 cells, MA inhibited the IκBα degradation, blocked NF-κB/p65 phosphorylation, and nuclear translocation. The phosphorylation of ERK, JNK, and p38 was attenuated by MA in IRI-induced kidney injury and H₂O₂-stimulated NRK52 cells. The expression levels of IL-1β, MCP-1, and ICAM-1 were upregulated in H₂O₂-stimulated NRK52E cells, which was attenuated by NF-κB inhibitor. H₂O₂ treatment increased the Bax/Bcl2 ratio and cleaved caspase-3 in NRK52E cells, which was counteracted by MAPK inhibitors. Together, our data demonstrate that MA suppresses IR-induced AKI injury through NF-κB and MAPK signaling pathways and that MA is a promising agent in the treatment of kidney diseases.

The inhibition of TRIM35-mediated TIGAR ubiquitination enhances mitochondrial fusion and alleviates renal ischemia-reperfusion injury

Tripartite motif 35 (TRIM35) is a member of the tripartite motif protein family and has been recognized to play a key role in immune-inflammatory diseases. However, the role of TRIM35 in renal ischemia-reperfusion injury (IRI) remains unclear. Our study proved that knockdown of TRIM35 alleviates kidney IRI by inhibiting oxidative stress and enhancing mitochondrial fusion. In addition, our experimental results found that TRIM35 interacts with TP53-induced glycolysis and apoptosis regulator (TIGAR) and promotes the polyubiquitination of TIGAR and induces its degradation in the proteasome pathway. Furthermore, TIGAR knockdown significantly inhibited mitochondrial fusion. These results indicate that TRIM35 is a potential therapeutic target for renal IRI.

S100A16 promotes acute kidney injury by activating HRD1-induced ubiquitination and degradation of GSK3β and CK1α

The pathogenesis of acute kidney injury (AKI) is associated with the activation of multiple signaling pathways, including Wnt/β-catenin signaling. However, the mechanism of Wnt/β-catenin pathway activation in renal interstitial fibroblasts during AKI is unclear. S100 calcium-binding protein A16 (S100A16), a new member of calcium-binding protein S100 family, is a multi-functional signaling factor involved in various pathogenies, including tumors, glycolipid metabolism disorder, and chronic kidney disease (CKD). We investigated the potential participation of S100A16 in Wnt/β-catenin pathway activation during AKI by subjecting wild-type (WT) and S100A16 knockout (S100A16+/−) mice to the ischemia–reperfusion injury (IRI), and revealed S100A16 upregulation in this model, in which knockout of S100A16 impeded the Wnt/β-catenin signaling pathway activation and recovered the expression of downstream hepatocyte growth factor (HGF). We also found that S100A16 was highly expressed in Platelet-derived growth factor receptor beta (PDGFRβ) positive renal fibroblasts in vivo. Consistently, in rat renal interstitial fibroblasts (NRK-49F cells), both hypoxia/reoxygenation and S100A16 overexpression exacerbated fibroblasts apoptosis and inhibited HGF secretion; whereas S100A16 knockdown or Wnt/β-catenin pathway inhibitor ICG-001 reversed these changes. Mechanistically, we showed that S100A16 promoted Wnt/β-catenin signaling activation via the ubiquitylation and degradation of β-catenin complex members, glycogen synthase kinase 3β (GSK3β) and casein kinase 1α (CK1α), mediated by E3 ubiquitin ligase, the HMG-CoA reductase degradation protein 1 (HRD1). Our study identified the S100A16 as a key regulator in the activation of Wnt/β-catenin signaling pathway in AKI.

Mechanisms and Models of Kidney Tubular Necrosis and Nephron Loss

Understanding nephron loss is a primary strategy for preventing CKD progression. Death of renal tubular cells may occur by apoptosis during developmental and regenerative processes. However, during 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. Although 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 versus nephron loss. Unraveling 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 the discussion of therapeutic options.

Artemisia capillaris Thunb. water extract attenuates adriamycin-induced renal injury by regulating apoptosis through the ROS/MAPK axis

Artemisia capillaris Thunb. is widely used in the treatment of kidney diseases, but the underlying mechanism remain elusive. Therefore, this study aimed to elucidate the mechanism of Artemisia capillaris Thunb. in alleviating renal injury. And renoprotective effects of freeze-dried powder of Artemisia capillaris Thunb. water extract (WAC) were assessed using adriamycin (ADR)-induced renal injury to the NRK-52E cells and ADR-induced renal injury Sprague-Dawley rats (SD rats) models. The results show that WAC could alleviate ADR-induced renal injury in SD rats and the NRK-52E cell line, improved renal function (BUN 9.73 ± 0.35 vs 7.13 ± 0.15, SCR 80.60 ± 1.68 vs 60.50 ± 1.42, ACR 11.50 ± 0.50 vs 8.526 ± 0.15) or cell viability (IC₅₀ = 1.08 µg/ml (ADR), cell viability increase 36.38% ± 6.74% (added 4 mg/ml WAC)), and reduced the apoptosis. Moreover, WAC inhibited the MAPK signal transduction, increased the expression of superoxide dismutase 1 (SOD1), and decreased the production of ROS. The treatment of N-acetylcysteine (NAC, antioxidant) in vitro showed that NAC inhibited apoptosis and alleviated renal injury by inhibiting oxidative stress and reducing the phosphorylation of proteins related to the MAPK signaling pathway. Therefore, these results suggested that WAC can alleviate ADR-induced renal injury and apoptosis by regulating the ROS/MAPK axis and has potential to be used as a renoprotective drug. PRACTICAL APPLICATIONS: Artemisia capillaris Thunb., which is a medicinal and edible plant, is widely used to treat kidney diseases in traditional Chinese medicine. The present research examined the renal protective effect of Artemisia capillaris Thunb. The results show that Artemisia capillaris Thunb. can effectively reduce renal tubular cell apoptosis through the ROS/MAPK axis in vivo and in vitro. In general, Artemisia capillaris Thunb. can be used as a potential herb to attenuate renal injury and further research can be conducted to explore its renoprotective mechanisms.

Rational design of stable heptamethine cyanines and development of a biomarker-activatable probe for detecting acute lung/kidney injuries via NIR-II fluorescence imaging

Heptamethine cyanines exhibiting high photo- and chemostability have been developed. And an activatable probe was developed for H2O2 to visualize acute lung and kidney injuries via NIR-II fluorescence imaging.

Genome-wide association studies identify the role of caspase-9 in kidney disease

Genome-wide association studies (GWAS) have identified hundreds of genetic risk regions for kidney dysfunction [estimated glomerular filtration rate (eGFR)]; however, the causal genes, cell types, and pathways are poorly understood. Integration of GWAS and human kidney expression of quantitative trait analysis using Bayesian colocations, transcriptome-wide association studies, and summary-based Mendelian randomization studies prioritized caspase-9 (CASP9) as a kidney disease risk gene. Human kidney single-cell epigenetic and immunostaining studies indicated kidney tubule cells as a disease-causing cell type. Mice with genetic deletion or pharmacological inhibition of CASP9 showed lower apoptosis while having improved mitophagy, resulting in dampened activation of cytosolic nucleotide sensing pathways (cGAS-STING), reduction of inflammation, and protection from acute kidney disease or renal fibrosis. In summary, here, we prioritized CASP9 as an eGFR GWAS target gene and demonstrated the causal role of CASP9 in kidney disease development via improving mitophagy and lowering inflammation and apoptosis.

Ganoderic Acids Prevent Renal Ischemia Reperfusion Injury by Inhibiting Inflammation and Apoptosis

Renal ischemia reperfusion injury (RIRI) is one of the main causes of acute kidney injury (AKI), which can lead to acute renal failure. The development of RIRI is so complicated that it involves many factors such as inflammatory response, oxidative stress and cell apoptosis. Ganoderic acids (GAs), as one of the main pharmacological components of Ganoderma lucidum, have been reported to possess anti-inflammatory, antioxidant, and other pharmacological effects. The study is aimed to investigate the protective effect of GAs on RIRI and explore related underlying mechanisms. The mechanisms involved were assessed by a mouse RIRI model and a hypoxia/reoxygenation model. Compared with sham-operated group, renal dysfunction and morphological damages were relieved markedly in GAs-pretreatment group. GAs pretreatment could reduce the production of pro-inflammatory factors such as IL-6, COX-2 and iNOS induced by RIRI through inhibiting TLR4/MyD88/NF-kB signaling pathway. Furthermore, GAs reduced cell apoptosis via the decrease of the ratios of cleaved caspase-8 and cleaved caspase-3. The experimental results suggest that GAs prevent RIRI by alleviating tissue inflammation and apoptosis and might be developed as a candidate drug for preventing RIRI-induced AKI.

Caspase-3-dependent peritubular capillary dysfunction is pivotal for the transition from acute to chronic kidney disease after acute ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a major risk factor for chronic renal failure. Caspase-3, an effector responsible for apoptosis execution, is activated within the peritubular capillary (PTC) in the early stage of IRI-induced acute kidney injury (AKI). Recently, we showed that caspase-3-dependent microvascular rarefaction plays a key role in fibrosis development after mild renal IRI. Here, we further characterized the role of caspase-3 in microvascular dysfunction and progressive renal failure in both mild and severe AKI, by performing unilateral renal artery clamping for 30/60 min with contralateral nephrectomy in wild-type (C57BL/6) or caspase-3-/- mice. In both forms of AKI, caspase-3-/- mice showed better long-term outcomes despite worse initial tubular injury. After 3 wk, they showed reduced PTC injury, decreased PTC collagen deposition and α-smooth muscle actin expression, and lower tubular injury scores compared with wild-type animals. Caspase-3-/- mice with severe IRI also showed better preservation of long-term renal function. Intravital imaging and microcomputed tomography revealed preserved PTC permeability and better terminal capillary density in caspase-3-/- mice. Collectively, these results demonstrate the pivotal importance of caspase-3 in regulating long-term renal function after IRI and establish the predominant role of PTC dysfunction as a major contributor to progressive renal dysfunction.NEW & NOTEWORTHY Our findings demonstrate the pivotal importance of caspase-3 in regulating renal microvascular dysfunction, fibrogenesis, and long-term renal impairment after acute kidney injury induced by ischemia-reperfusion injury. Furthermore, this study establishes the predominant role of peritubular capillary integrity as a major contributor to progressive renal dysfunction after ischemia-reperfusion injury.

GSDME-mediated pyroptosis promotes inflammation and fibrosis in obstructive nephropathy

Renal tubular cell (RTC) death and inflammation contribute to the progression of obstructive nephropathy, but its underlying mechanisms have not been fully elucidated. Here, we showed that Gasdermin E (GSDME) expression level and GSDME-N domain generation determined the RTC fate response to TNFα under the condition of oxygen-glucose-serum deprivation. Deletion of Caspase-3 (Casp3) or Gsdme alleviated renal tubule damage and inflammation and finally prevented the development of hydronephrosis and kidney fibrosis after ureteral obstruction. Using bone marrow transplantation and cell type-specific Casp3 knockout mice, we demonstrated that Casp3/GSDME-mediated pyroptosis in renal parenchymal cells, but not in hematopoietic cells, played predominant roles in this process. We further showed that HMGB1 released from pyroptotic RTCs amplified inflammatory responses, which critically contributed to renal fibrogenesis. Specific deletion of Hmgb1 in RTCs alleviated caspase11 and IL-1β activation in macrophages. Collectively, our results uncovered that TNFα/Casp3/GSDME-mediated pyroptosis is responsible for the initiation of ureteral obstruction-induced renal tubule injury, which subsequentially contributes to the late-stage progression of hydronephrosis, inflammation, and fibrosis. This novel mechanism will provide valuable therapeutic insights for the treatment of obstructive nephropathy.