Ischemic acute renal failure: An inflammatory disease?

The novel potential therapeutic target PSMP/MSMP promotes acute kidney injury via CCR2

Acute kidney injury (AKI) is a major worldwide health concern that currently lacks effective medical treatments. PSMP is a damage-induced chemotactic cytokine that acts as a ligand of CCR2 and has an unknown role in AKI. We have observed a significant increase in PSMP levels in the renal tissue, urine, and plasma of patients with AKI. PSMP deficiency improved kidney function and decreased tubular damage and inflammation in AKI mouse models induced by kidney ischemia-reperfusion injury, glycerol, and cisplatin. Single-cell RNA sequencing analysis revealed that Ly6Chi or F4/80lo infiltrated macrophages (IMs) were a major group of proinflammatory macrophages with strong CCR2 expression in AKI. We observed that PSMP deficiency decreased CCR2+Ly6Chi or F4/80lo IMs and inhibited M1 polarization in the AKI mouse model. Moreover, overexpressed human PSMP in the mouse kidney could reverse the attenuation of kidney injury in a CCR2-dependent manner, and this effect could be achieved without CCL2 involvement. Extracellular PSMP played a crucial role, and treatment with a PSMP-neutralizing antibody significantly reduced kidney injury in vivo. Therefore, PSMP might be a therapeutic target for AKI, and its antibody is a promising therapeutic drug for the treatment of AKI.

Protective effects of pioglitazone in renal ischemia-reperfusion injury (RIRI): focus on oxidative stress and inflammation

BACKGROUND

Renal ischemia-reperfusion injury (RIRI) is a critical phenomenon that compromises renal function and is the most serious health concern related to acute kidney injury (AKI). Pioglitazone (Pio) is a known agonist of peroxisome proliferator-activated receptor-gamma (PPAR-γ). PPAR-γ is a nuclear receptor that regulates genes involved in inflammation, metabolism, and cellular differentiation. Activation of PPAR-γ is associated with antiinflammatory and antioxidant effects, which are relevant to the pathophysiology of RIRI. This study aimed to investigate the protective effects of Pio in RIRI, focusing on oxidative stress and inflammation.

METHODS

We conducted a comprehensive literature search using electronic databases, including PubMed, ScienceDirect, Web of Science, Scopus, and Google Scholar.

RESULTS

The results of this study demonstrated that Pio has antioxidant, anti-inflammatory, and anti-apoptotic activities that counteract the consequences of RIRI. The study also discussed the underlying mechanisms, including the modulation of various pathways such as TNF-α, NF-κB signaling systems, STAT3 pathway, KIM-1 and NGAL pathways, AMPK phosphorylation, and autophagy flux. Additionally, the study presented a summary of various animal studies that support the potential protective effects of Pio in RIRI.

CONCLUSION

Our findings suggest that Pio could protect the kidneys from RIRI by improving antioxidant capacity and decreasing inflammation. Therefore, these findings support the potential of Pio as a therapeutic strategy for preventing RIRI in different clinical conditions.

Interferon-γ induces combined pyroptotic angiopathy and APOL1 expression in human kidney disease

Elevated interferon (IFN) signaling is associated with kidney diseases including COVID-19, HIV, and apolipoprotein-L1 (APOL1) nephropathy, but whether IFNs directly contribute to nephrotoxicity remains unclear. Using human kidney organoids, primary endothelial cells, and patient samples, we demonstrate that IFN-γ induces pyroptotic angiopathy in combination with APOL1 expression. Single-cell RNA sequencing, immunoblotting, and quantitative fluorescence-based assays reveal that IFN-γ-mediated expression of APOL1 is accompanied by pyroptotic endothelial network degradation in organoids. Pharmacological blockade of IFN-γ signaling inhibits APOL1 expression, prevents upregulation of pyroptosis-associated genes, and rescues vascular networks. Multiomic analyses in patients with COVID-19, proteinuric kidney disease, and collapsing glomerulopathy similarly demonstrate increased IFN signaling and pyroptosis-associated gene expression correlating with accelerated renal disease progression. Our results reveal that IFN-γ signaling simultaneously induces endothelial injury and primes renal cells for pyroptosis, suggesting a combinatorial mechanism for APOL1-mediated collapsing glomerulopathy, which can be targeted therapeutically.

Delayed Graft Function and the Renin-angiotensin System

Delayed graft function (DGF) is a form of acute kidney injury (AKI) and a common complication following kidney transplantation. It adversely influences patient outcomes increases the financial burden of transplantation, and currently, no specific treatments are available. In developing this form of AKI, activation of the renin-angiotensin system (RAS) has been proposed to play an important role. In this review, we discuss the role of RAS activation and its contribution to the pathophysiology of DGF following the different stages of the transplantation process, from procurement and ischemia to transplantation into the recipient and including data from experimental animal models. Deceased kidney donors, whether during cardiac or brain death, may experience activation of the RAS. That may be continued or further potentiated during procurement and organ preservation. Additional evidence suggests that during implantation of the kidney graft and reperfusion in the recipient, the RAS is activated and may likely remain activated, extrapolating from other forms of AKI where RAS overactivity is well documented. Of particular interest in this setting is the status of angiotensin-converting enzyme 2, a key RAS enzyme essential for the metabolism of angiotensin II and abundantly present in the apical border of the proximal tubules, which is the site of predominant injury in AKI and DGF. Interventions aimed at safely downregulating the RAS using suitable shorter forms of angiotensin-converting enzyme 2 could be a way to offer protection against DGF.

Reducing Oxidative Stress and Inflammation by Pyruvate Dehydrogenase Kinase 4 Inhibition Is Important in Prevention of Renal Ischemia-Reperfusion Injury in Diabetic Mice

BACKGRUOUND

Reactive oxygen species (ROS) and inflammation are reported to have a fundamental role in the pathogenesis of ischemia-reperfusion (IR) injury, a leading cause of acute kidney injury. The present study investigated the role of pyruvate dehydrogenase kinase 4 (PDK4) in ROS production and inflammation following IR injury.

METHODS

We used a streptozotocin-induced diabetic C57BL6/J mouse model, which was subjected to IR by clamping both renal pedicles. Cellular apoptosis and inflammatory markers were evaluated in NRK-52E cells and mouse primary tubular cells after hypoxia and reoxygenation using a hypoxia work station.

RESULTS

Following IR injury in diabetic mice, the expression of PDK4, rather than the other PDK isoforms, was induced with a marked increase in pyruvate dehydrogenase E1α (PDHE1α) phosphorylation. This was accompanied by a pronounced ROS activation, as well as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1) production. Notably, sodium dichloroacetate (DCA) attenuated renal IR injury-induced apoptosis which can be attributed to reducing PDK4 expression and PDHE1α phosphorylation levels. DCA or shPdk4 treatment reduced oxidative stress and decreased TNF-α, IL-6, IL-1β, and MCP-1 production after IR or hypoxia-reoxygenation injury.

CONCLUSION

PDK4 inhibition alleviated renal injury with decreased ROS production and inflammation, supporting a critical role for PDK4 in IR mediated damage. This result indicates another potential target for reno-protection during IR injury; accordingly, the role of PDK4 inhibition needs to be comprehensively elucidated in terms of mitochondrial function during renal IR injury.

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.

Cordyceps sinensis extract protects against acute kidney injury by inhibiting perforin expression in NK cells via the STING/IRF3 pathway

Acute kidney injury (AKI) is associated with immune cell activation and inflammation. However, the putative pathogenic mechanisms of this injury have not been thoroughly investigated. Natural killer (NK) cells play an important role in immune regulation; however, whether NK cells regulate AKI remains unclear. Cordyceps sinensis (CS), a modern Chinese patented medicine preparation, has been widely used in treating patients with chronic kidney disease (CKD) owing to its anti-inflammatory effects and maintenance of immune homeostasis. Whether 2'-deoxyadenosine, a major active component in CS, can ameliorate renal AKI by regulating immunity, particularly in NK cells, has not been reported. This study is the first to demonstrate how NK cells promote AKI by releasing perforin, interferon-gamma (IFN-γ) and other inflammatory factors in vivo and in vitro. Differential gene expression between AKI and normal tissues was assessed using bioinformatic analyses. Quantitative real-time PCR, western blotting, and immunohistochemical staining were used to detect target protein mRNA and protein expression. Levels of inflammatory factors were measured using enzyme-linked immunosorbent assay. We found the high doses of the 2'-deoxyadenosine treatment significantly alleviated FA-induced renal damage in vivo, and alleviated the NK cells of renal injury by activating the STING/IRF3 pathway to inhibit perforin release in vitro. The results showed that 2'-deoxyadenosine could mitigate AKI by downregulating the activity of NK cells (by decreasing the expressions of perforin and IFN-γ) and inhibiting the stimulator of interferon genes and phosphorylated IFN regulatory factor 3. This may provide valuable evidence supporting the clinical use of CS in treating patients with AKI.

High Mortality in Patients With an Ischemic Foot Ulcer Following Revascularization

Critical limb ischemia (CLI) is the advanced stage of peripheral arterial disease, which impairs blood flow to the extremities due to occlusion of arteries, in which patients suffer from ischemic pain at rest and gangrene or ulcers. It is frequently accompanied by major adverse cardiac events, resulting in exceedingly high mortality from a cardiac or cerebrovascular event in this population. Although there have been considerable amounts of novel and costly revascularization and wound dressing technology, mortality is still high. Therefore, the risk factors for such high mortality need to be addressed. This review aimed to summarize the potential risk factors for mortality in patients with CLI of the lower extremities. There are several such risk factors, including modifiable and nonmodifiable risk factors. This review further discusses some highlighted major modified risk factors, including renal failure, cardiovascular, and diabetes. The strategy of regular surveillance and modification of such risk factors in any patients with CLI should be developed.

Ceria-Based Therapeutic Antioxidants for Biomedical Applications

The growing interest in nanomedicine over the last 20 years has carved out a research field called "nanocatalytic therapy," where catalytic reactions mediated by nanomaterials are employed to intervene in disease-critical biomolecular processes. Among many kinds of catalytic/enzyme-mimetic nanomaterials investigated thus far, ceria nanoparticles stand out from others owing to their unique scavenging properties against biologically noxious free radicals, including reactive oxygen species (ROS) and reactive nitrogen species (RNS), by exerting enzyme mimicry and nonenzymatic activities. Much effort has been made to utilize ceria nanoparticles as self-regenerating antioxidative and anti-inflammatory agents for various kinds of diseases, given the detrimental effects of ROS and RNS therein that need alleviation. In this context, this review is intended to provide an overview as to what makes ceria nanoparticles merit attention in disease therapy. The introductory part describes the characteristics of ceria nanoparticles as an oxygen-deficient metal oxide. The pathophysiological roles of ROS and RNS are then presented, as well as their scavenging mechanisms by ceria nanoparticles. Representative examples of recent ceria-nanoparticle-based therapeutics are summarized by categorization into organ and disease types, followed by the discussion on the remaining challenges and future research directions.

Social isolation, loneliness, and the risk of incident acute kidney injury in middle-aged and older adults: A prospective cohort study

OBJECTIVE

The relationships of social isolation and loneliness with acute kidney injury (AKI) risk remained uncertain. We aimed to investigate the associations of social isolation and loneliness with incident AKI.

METHODS

450,868 participants without prior AKI were included from the UK Biobank. The social isolation index was constructed based on living alone, social contact, and participation in social activities. Loneliness was assessed by asking about "Do you often feel lonely?". The study outcome was incident AKI.

RESULTS

During a median follow-up of 12.0 years, 18,679 (4.1%) participants developed AKI, including 18,428 participants ascertained by hospital admission records with a median duration of hospitalization of 3 (25th-75th, 1-8) days. The hazard ratio for incident AKI for social isolation compared with no social isolation was 1.50 (95% CI: 1.44-1.55) after adjusting for age and race (minimally adjusted), and was 1.10 (95% CI: 1.06-1.14) after further adjusting for socioeconomic factors, health behaviors, biological and health-related factors, psychologic factors, and loneliness (fully adjusted). The minimally adjusted and fully adjusted hazard ratios for incident AKI for loneliness compared with no loneliness was 1.57 (95% CI: 1.52-1.62), and 1.10 (95% CI: 1.06-1.15), respectively. In the fully adjusted models, the highest risk of AKI was found in those with both social isolation and loneliness. Living alone and less social contact, rather than less participation in social activities, were significantly associated with a higher risk of incident AKI.

CONCLUSIONS

Both social isolation and loneliness were independently and significantly associated with a higher risk of incident AKI.

The nuclear factor kappa B signaling pathway is a master regulator of renal fibrosis

Renal fibrosis is increasingly recognized as a global public health problem. Acute kidney injury (AKI) and chronic kidney disease (CKD) both result in renal fibrosis. Oxidative stress and inflammation play central roles in progressive renal fibrosis. Oxidative stress and inflammation are closely linked and form a vicious cycle in which oxidative stress induces inflammation through various molecular mechanisms. Ample evidence has indicated that a hyperactive nuclear factor kappa B (NF-ƙB) signaling pathway plays a pivotal role in renal fibrosis. Hyperactive NF-ƙB causes the activation and recruitment of immune cells. Inflammation, in turn, triggers oxidative stress through the production of reactive oxygen species and nitrogen species by activating leukocytes and resident cells. These events mediate organ injury through apoptosis, necrosis, and fibrosis. Therefore, developing a strategy to target the NF-ƙB signaling pathway is important for the effective treatment of renal fibrosis. This Review summarizes the effect of the NF-ƙB signaling pathway on renal fibrosis in the context of AKI and CKD (immunoglobulin A nephropathy, membranous nephropathy, diabetic nephropathy, hypertensive nephropathy, and kidney transplantation). Therapies targeting the NF-ƙB signaling pathway, including natural products, are also discussed. In addition, NF-ƙB-dependent non-coding RNAs are involved in renal inflammation and fibrosis and are crucial targets in the development of effective treatments for kidney disease. This Review provides a clear pathophysiological rationale and specific concept-driven therapeutic strategy for the treatment of renal fibrosis by targeting the NF-ƙB signaling pathway.

Innate immune modulation in transplantation: mechanisms, challenges, and opportunities

Organ transplantation is characterized by a sequence of steps that involve operative trauma, organ preservation, and ischemia-reperfusion injury in the transplant recipient. During this process, the release of damage-associated molecular patterns (DAMPs) promotes the activation of innate immune cells via engagement of the toll-like receptor (TLR) system, the complement system, and coagulation cascade. Different classes of effector responses are then carried out by specialized populations of macrophages, dendritic cells, and T and B lymphocytes; these play a central role in the orchestration and regulation of the inflammatory response and modulation of the ensuing adaptive immune response to transplant allografts. Organ function and rejection of human allografts have traditionally been studied through the lens of adaptive immunity; however, an increasing body of work has provided a more comprehensive picture of the pivotal role of innate regulation of adaptive immune responses in transplant and the potential therapeutic implications. Herein we review literature that examines the repercussions of inflammatory injury to transplantable organs. We highlight novel concepts in the pathophysiology and mechanisms involved in innate control of adaptive immunity and rejection. Furthermore, we discuss existing evidence on novel therapies aimed at innate immunomodulation and how this could be harnessed in the transplant setting.

The protective effect of allium cepa against ethylene glycol-induced kidney stones in rats

1Background

Kidney stones is one of the serious medical conditions affecting populations worldwide. So, we aimed in this study to investigate the protective effect of allium cepa administration against KSD.

2Methods

24 adult male albino rats were assigned into 3 groups; group I: control group; group II: received ethylene glycol (EG) in the drinking water for 4 weeks; and group III received EG in the drinking water plus freshly prepared allium cepa extract (ACE) for 4 weeks. Renal function tests and urine analysis were done. Tissue oxidative stress markers (SOD and MDA) were assessed, and kidney expression of SIRT-1, Beclin, LC3, osteopontin, and Regucalcin were measured by RT-qPCR. Histopathological assessment and immunohistochemistry for Bax, Beclin-1 and TNF-α were performed.

3Results

There was a significant improved kidney function tests in the ACE received group compared to EG group (P < 0.001). The present study showed less stones formation and apoptosis with decreased osteopontin and autophagy genes expression in the ACE received group compared to EG group (P < 0.001). While, regucalcin and SIRT-1 genes showed higher expression in the former group than the later group (P < 0.001).

4 Conclusion

Alium Cepa extract administration has a significant protective effect against kidney stones formation.

Network pharmacology and in vitro experimental verification to reveal the mechanism of Astragaloside IV against kidney ischemia-reperfusion injury

Ischemic acute kidney injury (AKI) is a prevalent disorder among hospitalized patients worldwide. Astragaloside IV (AS-IV) has been shown to protect against ischemic AKI. However, the specific effects and mechanisms of AS-IV on alleviating kidney ischemia-reperfusion (I/R) injury remain unclear. The objective of this research was to elucidate the regulatory targets and mechanisms through which AS-IV protects kidney I/R injury. A combination of network pharmacology, molecular docking, molecular dynamics (MD) simulation, pharmacodynamic study and Western blot were employed to explore the underlying mechanisms. Network pharmacology revealed that ferroptosis was a potential mechanism of AS-IV against kidney I/R injury. Molecular docking and MD simulations demonstrated strong binding affinity between the GPX4/SLC7A11 and AS-IV. The experimental verification demonstrated that AS-IV improved cell proliferation, decreased the level of ROS and Fe2+, and increased the expressions of GPX4 and SLC7A11 as same as Ferrostatin-1 in OGD/R-injured HUVECs. In conclusion, AS-IV had a significant inhibition on ferroptosis in kidney I/R injury, providing a new perspective for drug development on kidney I/R injury. Definitely, further exploration in vivo is necessary to fully understand whether AS-IV alleviates kidney I/R injury through inhibiting endothelial ferroptosis.

Advances in the study of ELABELA in renal physiological functions and related diseases

ELABELA (ELA), also known as Toddler or Apela, is a novel endogenous ligand of the angiotensin receptor AT1-related receptor protein (APJ). ELA is highly expressed in human embryonic, cardiac, and renal tissues and involves various biological functions, such as embryonic development, blood circulation regulation, and maintaining body fluid homeostasis. ELA is also closely related to the occurrence and development of acute kidney injury, hypertensive kidney damage, diabetic nephropathy, renal tumors, and other diseases. Understanding the physiological role of ELA and its mechanism of action in kidney-related diseases would provide new targets and directions for the clinical treatment of kidney diseases.

Acute Kidney Injury by Ischemia/Reperfusion and Extracellular Vesicles

Acute kidney injury (AKI) is often caused by ischemia-reperfusion injury (IRI). IRI significantly affects kidney metabolism, which elicits pro-inflammatory responses and kidney injury. The ischemia/reperfusion of the kidney is associated with transient high mitochondrial-derived reactive oxygen species (ROS) production rates. Excessive mitochondrial-derived ROS damages cellular components and, together with other pathogenic mechanisms, elicits a range of acute injury mechanisms that impair kidney function. Mitochondrial-derived ROS production also stimulates epithelial cell secretion of extracellular vesicles (EVs) containing RNAs, lipids, and proteins, suggesting that EVs are involved in AKI pathogenesis. This literature review focuses on how EV secretion is stimulated during ischemia/reperfusion and how cell-specific EVs and their molecular cargo may modify the IRI process. Moreover, critical pitfalls in the analysis of kidney epithelial-derived EVs are described. In particular, we will focus on how the release of kidney epithelial EVs is affected during tissue analyses and how this may confound data on cell-to-cell signaling. By increasing awareness of methodological pitfalls in renal EV research, the risk of false negatives can be mitigated. This will improve future EV data interpretation regarding EVs contribution to AKI pathogenesis and their potential as biomarkers or treatments for AKI.

Phytocompounds from Amazonian Plant Species against Acute Kidney Injury: Potential Nephroprotective Effects

There are several Amazonian plant species with potential pharmacological validation for the treatment of acute kidney injury, a condition in which the kidneys are unable to adequately filter the blood, resulting in the accumulation of toxins and waste in the body. Scientific production on plant compounds capable of preventing or attenuating acute kidney injury-caused by several factors, including ischemia, toxins, and inflammation-has shown promising results in animal models of acute kidney injury and some preliminary studies in humans. Despite the popular use of Amazonian plant species for kidney disorders, further pharmacological studies are needed to identify active compounds and subsequently conduct more complex preclinical trials. This article is a brief review of phytocompounds with potential nephroprotective effects against acute kidney injury (AKI). The classes of Amazonian plant compounds with significant biological activity most evident in the consulted literature were alkaloids, flavonoids, tannins, steroids, and terpenoids. An expressive phytochemical and pharmacological relevance of the studied species was identified, although with insufficiently explored potential, mainly in the face of AKI, a clinical condition with high morbidity and mortality.

Natural Products in Renal-Associated Drug Discovery

The global increase in the incidence of kidney failure constitutes a major public health problem. Kidney disease is classified into acute and chronic: acute kidney injury (AKI) is associated with an abrupt decline in kidney function and chronic kidney disease (CKD) with chronic renal failure for more than three months. Although both kidney syndromes are multifactorial, inflammation and oxidative stress play major roles in the diversity of processes leading to these kidney malfunctions. Here, we reviewed various publications on medicinal plants with antioxidant and anti-inflammatory properties with the potential to treat and manage kidney-associated diseases in rodent models. Additionally, we conducted a meta-analysis to identify gene signatures and associated biological processes perturbed in human and mouse cells treated with antioxidants such as epigallocatechin gallate (EGCG), the active ingredient in green tea, and the mushroom Ganoderma lucidum (GL) and in kidney disease rodent models. We identified EGCG- and GL-regulated gene signatures linked to metabolism; inflammation (NRG1, E2F1, NFKB1 and JUN); ion signalling; transport; renal processes (SLC12A1 and LOX) and VEGF, ERBB and BDNF signalling. Medicinal plant extracts are proving to be effective for the prevention, management and treatment of kidney-associated diseases; however, more detailed characterisations of their targets are needed to enable more trust in their application in the management of kidney-associated diseases.

Kaempferide ameliorates cisplatin-induced nephrotoxicity via inhibiting oxidative stress and inducing autophagy

Acute kidney injury (AKI) caused by anti-tumor drugs, such as cisplatin, is a severe complication with no effective treatment currently, leading to the reduction or discontinuation of chemotherapy. Natural products or herbal medicines are gradually considered as promising agents against cisplatin-induced AKI with the advantages of multi-targeting, multi-effects, and less resistance. In this study, we investigated the effects of kaempferide, a natural flavonoid extracted from the rhizome of Kaempferia galanga, in experimental AKI models in vitro and in vivo. We first conducted pharmacokinetic study in mice and found a relative stable state of kaempferide with a small amount of conversion into kaempferol. We showed that both kaempferide (10 μM) and kaempferol (10 μM) significantly inhibited cisplatin-caused injuries in immortalized proximal tubule epithelial cell line HK-2. In AKI mice induced by injection of a single dose of cisplatin (15 mg/kg), oral administration of kaempferide (50 mg/kg) either before or after cisplatin injection markedly improved renal function, and ameliorated renal tissue damage. We demonstrated that kaempferide inhibited oxidative stress and induced autophagy in cisplatin-treated mice and HK-2 cells, thus increasing tubular cell viability and decreasing immune responses to attenuate the disease progression. In addition, treatment with kaempferide significantly ameliorated ischemia-reperfusion-induced renal injury in vitro and in vivo. We conclude that kaempferide is a promising natural product for treating various AKI. This study has great implications for promotion of its use in healthcare products, and help to break through the limited use of cisplatin in the clinic.

Inflammatory mediators act at renal pericytes to elicit contraction of vasa recta and reduce pericyte density along the kidney medullary vascular network

Introduction: Regardless of initiating cause, renal injury promotes a potent pro-inflammatory environment in the outer medulla and a concomitant sustained decrease in medullary blood flow (MBF). This decline in MBF is believed to be one of the critical events in the pathogenesis of acute kidney injury (AKI), yet the precise cellular mechanism underlying this are still to be fully elucidated. MBF is regulated by contractile pericyte cells that reside on the descending vasa recta (DVR) capillaries, which are the primary source of blood flow to the medulla. Methods: Using the rat and murine live kidney slice models, we investigated the acute effects of key medullary inflammatory mediators TNF-α, IL-1β, IL-33, IL-18, C3a and C5a on vasa recta pericytes, the effect of AT1-R blocker Losartan on pro-inflammatory mediator activity at vasa recta pericytes, and the effect of 4-hour sustained exposure on immunolabelled NG2+ pericytes. Results and discussion: Exposure of rat and mouse kidney slices to TNF-α, IL-18, IL-33, and C5a demonstrated a real-time pericyte-mediated constriction of DVR. When pro-inflammatory mediators were applied in the presence of Losartan the inflammatory mediator-mediated constriction that had previously been observed was significantly attenuated. When live kidney slices were exposed to inflammatory mediators for 4-h, we noted a significant reduction in the number of NG2+ positive pericytes along vasa recta capillaries in both rat and murine kidney slices. Data collected in this study demonstrate that inflammatory mediators can dysregulate pericytes to constrict DVR diameter and reduce the density of pericytes along vasa recta vessels, further diminishing the regulatory capacity of the capillary network. We postulate that preliminary findings here suggest pericytes play a role in AKI.

Loss of renal tubular G9a benefits acute kidney injury by lowering focal lipid accumulation via CES1

Surgery-induced renal ischemia and reperfusion (I/R) injury and nephrotoxic drugs like cisplatin can cause acute kidney injury (AKI), for which there is no effective therapy. Lipid accumulation is evident following AKI in renal tubules although the mechanisms and pathological effects are unclear. Here, we report that Ehmt2-encoded histone methyltransferase G9a is upregulated in patients and mouse kidneys after AKI. Renal tubular specific knockout of G9a (Ehmt2Ksp ) or pharmacological inhibition of G9a alleviates lipid accumulation associated with AKI. Mechanistically, G9a suppresses transcription of the lipolytic enzyme Ces1; moreover, G9a and farnesoid X receptor (FXR) competitively bind to the same promoter regions of Ces1. Ces1 is consistently observed to be downregulated in the kidney of AKI patients. Pharmacological inhibition of Ces1 increases lipid accumulation, exacerbates renal I/R-injury and eliminates the beneficial effects on AKI observed in Ehmt2Ksp mice. Furthermore, lipid-lowering atorvastatin and an FXR agonist alleviate AKI by activating Ces1 and reducing renal lipid accumulation. Together, our results reveal a G9a/FXR-Ces1 axis that affects the AKI outcome via regulating renal lipid accumulation.

Acute kidney injury in diabetic patients: A narrative review

Diabetes mellitus (DM) is the most common cause of chronic kidney disease, which leads to end-stage renal failure worldwide. Glomerular damage, renal arteriosclerosis, and atherosclerosis are the contributing factors in diabetic patients, leading to the progression of kidney damage. Diabetes is a distinct risk factor for acute kidney injury (AKI) and AKI is associated with faster advancement of renal disease in patients with diabetes. The long-term consequences of AKI include the development of end-stage renal disease, higher cardiovascular and cerebral events, poor quality of life, and high morbidity and mortality. In general, not many studies discussed extensively "AKI in DM." Moreover, articles addressing this topic are scarce. It is also important to know the cause of AKI in diabetic patients so that timely intervention and preventive strategies can be implemented to decrease kidney injury. Aim of this review article is to address the epidemiology of AKI, its risk factors, different pathophysiological mechanisms, how AKI differs between diabetic and nondiabetic patients and its preventive and therapeutic implications in diabetics. The increasing occurrence and prevalence of AKI and DM, as well as other pertinent issues, motivated us to address this topic.

Acute kidney injury in diabetes mellitus: Epidemiology, diagnostic, and therapeutic concepts

Acute kidney injury (AKI) and diabetes mellitus (DM) are public health problems that cause a high socioeconomic burden worldwide. In recent years, the landscape of AKI etiology has shifted: Emerging evidence has demonstrated that DM is an independent risk factor for the onset of AKI, while an alternative perspective considers AKI as a bona fide complication of DM. Therefore, it is necessary to systematically characterize the features of AKI in DM. In this review, we summarized the epidemiology of AKI in DM. While focusing on circulation- and tissue-specific microenvironment changes after DM, we described the active cellular and molecular mechanisms of increased kidney susceptibility to AKI under DM stress. We also reviewed the current diagnostic and therapeutic strategies for AKI in DM recommended in the clinic. Updated recognition of the epidemiology, pathophysiology, diagnosis, and medications of AKI in DM is believed to reveal a path to mitigate the frequency of AKI and DM comorbidity that will ultimately improve the quality of life in DM patients.

Protective effect of IAXO-102 on renal ischemia-reperfusion injury in rats

Ischemia/reperfusion injury (IRI) is a common cause of kidney damage, characterized by oxidative stress and inflammation. In this study, we investigated the potential protective effects of IAXO-102, a chemical compound, on experimentally induced IRI in male rats. The bilateral renal IRI model was used, with 24 adult male rats randomly divided into four groups (N=6): sham group (laparotomy without IRI induction), control group (laparotomy plus bilateral IRI for 30 minutes followed by 2 hours of reperfusion), vehicle group (same as control but pre-injected with the vehicle), and treatment group (similar to control but pre-injected with IAXO-102). We measured several biomarkers involved in IRI pathophysiology using enzyme-linked immunosorbent assay (ELISA), including High mobility group box1 (HMGB1), nuclear factor kappa b-p65 (NF-κB p65), interleukin beta-1 (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), 8-isoprostane, Bcl-2 associated X protein (BAX), heat shock protein 27 (HSP27), and Bcl-2. Statistical analysis was performed using one-way ANOVA and Tukey post hoc tests. Our results showed that IAXO-102 significantly improved kidney function, reduced histological alterations, and decreased the inflammatory response (IL-1, IL-6, and TNF) caused by IRI. IAXO-102 also decreased apoptosis by reducing pro-apoptotic Bax and increasing anti-apoptotic Bcl-2 without impacting HSP27. In conclusion, our findings suggest that IAXO-102 had a significant protective effect against IRI damage in the kidneys.

Prognostic value of C-reactive protein to albumin ratio for mortality in acute kidney injury

BACKGROUND

Inflammation plays an important role in the development of acute kidney injury (AKI). However, there are few studies exploring the prognostic influence of C-reactive protein to albumin ratio (CAR) among AKI patients. In this study, we investigated whether CAR could be a useful marker to predict the mortality of AKI.

METHODS

A total of 358 AKI patients were extracted from the Medical Information Mart for Intensive Care III (MIMIC III) database. C-reactive protein (CRP) and albumin were measured at ICU admission. The clinical outcome was 365-day mortality. Cox proportional hazards model and Kaplan-Meier survival analysis were conducted to evaluate the association between CAR and outcome.

RESULTS

Compared with patients in the survival group, nonsurvivors had higher CAR levels. The area under the receiver operating characteristic (ROC) curve of CAR was higher than that of CRP and albumin for mortality (0.64 vs. 0.63, 0.59, respectively). The cut-off point of CAR for mortality was 7.23. In Cox proportional-hazard regression analysis, CAR (hazards ratio (HR) =2.04, 95% confidence interval (CI) =1.47-2.85, p < 0.001 for higher CAR) and Simplified Acute Physiology Score II (HR = 1.02, 95%CI = 1.00-1.03, p = 0.004) were independent predictors of 365-day mortality.

CONCLUSIONS

Our study demonstrated that a higher level of CAR was associated with 365-day mortality in AKI patients.

RNA sequencing and bioinformatics analysis of circular RNAs in asphyxial newborns with acute kidney injury

As one kind of novel noncoding RNA, circular RNAs (circRNAs) are involved in different biological processes. Although growing evidences have supported the important role of circRNAs in renal diseases, the mechanism remains unclear in neonatal acute kidney injury (AKI). High-throughput sequencing analysis was used to investigate the expression of circRNAs between hypoxia-induced AKI neonates and controls. Bioinformatics analysis was conducted to predict the function of differentially expressed circRNAs. Finally, the differentially expressed circRNAs were screened and determined by quantitative real-time PCR (qPCR). (1) A total of 296 differentially expressed circRNAs were identified (Fold change >2 and p < 0.05). Of them, 184 circRNAs were markedly upregulated, and 112 were significantly downregulated in the AKI group. (2) The pathway analysis showed that ubiquitin-mediated proteolysis, renal cell carcinoma, Jak-STAT, and HIF-1 signaling pathways participated in AKI. (3) Top five upregulated and five downregulated circRNAs with higher fold changes were selected for qPCR validation. Hsa_circ_0008898 (Fold Change = 5.48, p = 0.0376) and hsa_circ_0005519 (Fold Change = 4.65, p = 0.0071) were significantly upregulated, while hsa_circ_0132279 (Fold Change = -4.47, p = 0.0008), hsa_circ_0112327 (Fold Change = -4.26, p = 0.0048), and hsa_circ_0017647 (Fold Change = -4.15, p = 0.0313) were significantly downregulated in asphyxia-induced AKI group compared with the control group. This study could contribute to future research on neonatal AKI and facilitate the identification of novel therapeutic targets.

Toll-like Receptor 4 in Acute Kidney Injury

Acute kidney injury (AKI) is a common and devastating pathologic condition, associated with considerable high morbidity and mortality. Although significant breakthroughs have been made in recent years, to this day no effective pharmacological therapies for its treatment exist. AKI is known to be connected with intrarenal and systemic inflammation. The innate immune system plays an important role as the first defense response mechanism to tissue injury. Toll-like receptor 4 (TLR4) is a well-characterized pattern recognition receptor, and increasing evidence has shown that TLR4 mediated inflammatory response, plays a pivotal role in the pathogenesis of acute kidney injury. Pathogen-associated molecular patterns (PAMPS), which are the conserved microbial motifs, are sensed by these receptors. Endogenous molecules generated during tissue injury, and labeled as damage-associated molecular pattern molecules (DAMPs), also activate pattern recognition receptors, thereby offering an understanding of sterile types of inflammation. Excessive, uncontrolled and/or sustained activation of TLR4, may lead to a chronic inflammatory state. In this review we describe the role of TLR4, its endogenous ligands and activation in the inflammatory response to ischemic/reperfusion-induced AKI and sepsis-associated AKI. The potential regeneration signaling patterns of TLR4 in acute kidney injury, are also discussed.

PIM1 attenuates renal ischemia-reperfusion injury by inhibiting ASK1-JNK/P38

Renal ischemia-reperfusion injury (IRI) is the main cause of acute kidney injury (AKI), yet therapeutic approaches to alleviate IRI remain limited. PIM1 (provirus integration site for Moloney murine leukemia virus 1) is a constitutive serine threonine kinase that phosphorylates various substrates to regulate cell death and survival. However, the role of PIM1 in renal IRI remains unclear. This study aims to investigate the effect of PIM1 on renal IRI and explore its downstream regulatory mechanism. In this study, we inhibited or overexpressed PIM1 in mice and cultured proximal tubular cells, and then induced renal IRI model in vivo and hypoxia reoxygenation (HR) model in vitro. Renal function, renal structure injuries and cellular death were assessed to reflect the extent of IRI. The expression of PIM1 and the levels of ASK1, MAPK and their phosphorylated forms were detected by immunoblot. RNA sequencing of kidney cortex was performed to analyze downstream pathway of PIM1 in renal IRI. The results showed that PIM1 expression was significantly upregulated in renal IRI mouse model and in renal tubular cell HR model. AZD1208 (a PIM1 inhibitor) aggravated renal IRI, while PIM1 overexpression ameliorated renal IRI. This was involved in the regulation of the ASK1-MAPK pathway. Moreover, results demonstrated that ASK1 was a downstream target of PIM1 by administering Selonsertib (an inhibitor of ASK1 activity), and inhibiting ASK1 alleviated cell death after HR in PIM1 knockdown cells by reducing JNK/P38 activation. In conclusion, this study elucidated the protective effect of PIM1 on renal IRI, and the underlying mechanism may be related to ASK1-JNK/P38 signaling pathway. Taken together, PIM1 may be a potential therapeutic target for renal IRI.

TSG-6 (Tumor Necrosis Factor-α-Stimulated Gene/Protein-6): An Emerging Remedy for Renal Inflammation

The inflammatory response is a major pathological feature in most kidney diseases and often evokes compensatory mechanisms. Recent evidence suggests that TSG-6 (tumor necrosis factor-α-stimulated gene/protein-6) plays a pivotal role in anti-inflammation in various renal diseases, including immune-mediated and nonimmune-mediated renal diseases. TSG-6 has a diverse repertoire of anti-inflammatory functions: it potentiates antiplasmin activity of IαI (inter-α-inhibitor) by binding to its light chain, crosslinks hyaluronan to promote its binding to cell surface receptor CD44, and thereby regulate the migration and adhesion of lymphocytes, inhibits chemokine-stimulated transendothelial migration of neutrophils by directly interacting with the glycosaminoglycan binding site of CXCL8 (CXC motif chemokine ligand-8), and upregulates COX-2 (cyclooxygenase-2) to produce anti-inflammatory metabolites. Hopefully, further developments can target this anti-inflammatory molecule to the kidney and harness its remedial properties. This review provides an overview of the emerging role of TSG-6 in blunting renal inflammation.

microRNA-338-3p suppresses lipopolysaccharide-induced inflammatory response in HK-2 cells

BACKGROUND

Inflammation is the most common cause of kidney damage, and inflammatory responses in a number of diseases are mediated by microRNA-338-3p (miR-338-3p). However, there are only a few reports which described the regulation of miR-338-3p in human proximal tubular cells. The goal of this study was to see how miR-338-3p affected lipopolysaccharide (LPS)-caused inflammatory response in HK-2 cells.

METHODS

LPS was used to construct an inflammatory model in HK-2 cells. miR-338-3p mimic was used to increase the levels of miR-338-3p in HK-2 cells. MTT, JC-1 staining, and apoptosis assays were used to detect cell viability, mitochondrial membrane potential (MMP), and apoptosis, respectively. The production of inflammatory factors and the levels of p38, p65, phospho-p65, phospho-p38, Bax, Bcl-2, cleaved caspase-9, and cleaved caspase-3 were investigated using real-time polymerase chain reaction, western blotting, or enzyme-linked immunosorbent assay.

RESULTS

The levels of miR-338-3p were significantly lower in serum from patients with sepsis-induced kidney injury compared to the serum from healthy volunteers (P < 0.05). LPS reduced the level of miR-338-3p in HK-2 cells (P < 0.05). HK-2 cell viability, mitochondrial membrane potential, and Bcl-2 mRNA and protein levels were decreased by LPS (all P < 0.05). Apoptosis, the mRNA and protein levels of inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α) and Bax, and the levels of cleaved caspase-9 and caspase-3 were increased by LPS (all P < 0.05). Raising the level of miR-338-3p mitigated these effects of LPS (all P < 0.05).

CONCLUSION

LPS-induced inflammation in HK-2 cells is reduced by miR-338-3p.

Effects of inflammation and oxidative stress on postoperative delirium in cardiac surgery

The past decade has witnessed unprecedented medical progress, which has translated into cardiac surgery being increasingly common and safe. However, complications such as postoperative delirium remain a major concern. Although the pathophysiological changes of delirium after cardiac surgery remain poorly understood, it is widely thought that inflammation and oxidative stress may be potential triggers of delirium. The development of delirium following cardiac surgery is associated with perioperative risk factors. Multiple interventions are being explored to prevent and treat delirium. Therefore, research on the potential role of biomarkers in delirium as well as identification of perioperative risk factors and pharmacological interventions are necessary to mitigate the development of delirium.

Pioglitazone modulates immune activation and ameliorates inflammation induced by injured renal tubular epithelial cells via PPARγ/miRNA‑124/STAT3 signaling

Acute kidney injury (AKI) is commonly a result of renal ischemia reperfusion injury (IRI), which produces clinical complications characterized by the rapid deterioration of renal function, leading to chronic kidney disease and increases the risk of morbidity and mortality. Currently, only supportive treatment is available. AKI, which is accompanied by immune activation and inflammation, is caused by proximal tubular injury. The present study investigated the role of tubular epithelial cells as drivers of inflammation in renal IRI and their potential function as antigen-presenting cells, as well as the molecular mechanisms by which peroxisome proliferator-activated receptor-γ (PPARγ) agonists [such as pioglitazone (Pio)] exert reno-protective action in renal IRI. A total of 50 Wistar male albino rats were divided into five groups: Sham + DMSO, Sham + Pio, IRI + DMSO, IRI + prophylactic preoperative (pre) Pio and IRI + postoperative Pio. The histopathological changes in renal tissue samples and the renal epithelial cell expression of CD86, miRNA-124, STAT3, pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and Arginase-II were analyzed by immunohistochemistry, reverse transcription-quantitative PCR, western blotting and ELISA respectively. IRI was a potent inducer for CD86 immunoexpression. An ameliorative action of Pio was demonstrated via decreased CD86 immunoexpression, upregulation of miRNA-124, decreased STAT3 expression and beneficial anti-inflammatory effects. The tubular epithelium served a notable role in the inflammatory response in renal IRI. Pio exerted its anti-inflammatory effects via PPARγ/miRNA-124/STAT3 signaling.

Locally transplanted human urine-induced nephron progenitor cells contribute to renal repair in mice kidney with diabetic nephropathy

Chronic Kidney Disease (CKD) is increasingly recognized as a global public health issue. Diabetic nephropathy (DN), also known as diabetic kidney disease, is a leading cause of CKD. Regenerative medicine strategy employing nephron progenitor cells (NPCs) is worthy of consideration as an alternative to shortage of donor organs for kidney transplantation. In previous study, we successfully generated induced NPCs (iNPCs) from human urine-derived cells that resembled human embryonic stem cell-derived NPCs. Here, we aimed to investigate the therapeutic potential of iNPCs in DN animal model. The results revealed the therapeutic effect of iNPCs as follows: (1) diminished glomerular hypertrophy, (2) reduced tubulointerstitial fibrosis, (3) low blood urea nitrogen, serum creatinine and albuminuria value, (4) decreased inflammation/fibrosis, (5) enhanced renal regeneration and (6) confirmed safety. This study demonstrates that human iNPCs have a therapeutic potential as a cell source for transplantation in patients with kidney diseases.

Molecular and cellular mechanisms involved in tissue-specific metabolic modulation by SARS-CoV-2

Coronavirus disease 2019 (COVID-19) is triggered by the SARS-CoV-2, which is able to infect and cause dysfunction not only in lungs, but also in multiple organs, including central nervous system, skeletal muscle, kidneys, heart, liver, and intestine. Several metabolic disturbances are associated with cell damage or tissue injury, but the mechanisms involved are not yet fully elucidated. Some potential mechanisms involved in the COVID-19-induced tissue dysfunction are proposed, such as: (a) High expression and levels of proinflammatory cytokines, including TNF-α IL-6, IL-1β, INF-α and INF-β, increasing the systemic and tissue inflammatory state; (b) Induction of oxidative stress due to redox imbalance, resulting in cell injury or death induced by elevated production of reactive oxygen species; and (c) Deregulation of the renin-angiotensin-aldosterone system, exacerbating the inflammatory and oxidative stress responses. In this review, we discuss the main metabolic disturbances observed in different target tissues of SARS-CoV-2 and the potential mechanisms involved in these changes associated with the tissue dysfunction.

View of the Renin-Angiotensin System in Acute Kidney Injury Induced by Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion injury (RIRI) is a sequence of complicated events that is defined as a reduction of the blood supply followed by reperfusion. RIRI is the leading cause of acute kidney injury (AKI). Among the diverse mediators that take part in RIRI-induced AKI, the renin-angiotensin system (RAS) plays an important role via conventional (angiotensinogen, renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and Ang II type 1 receptor (AT1R)) and nonconventional (ACE2, Ang 1-7, Ang 1-9, AT2 receptor (AT2R), and Mas receptor (MasR)) axes. RIRI alters the balance of both axes so that RAS can affect RIRI-induced AKI. In overall, the alteration of Ang II/AT1R and AKI by RIRI is important to consider. This review has looked for the effects and interactions of RAS activities during RIRI conditions.

The Role of Innate Immune Cells in the Prediction of Early Renal Allograft Injury Following Kidney Transplantation

Background: Despite recent advances and refinements in perioperative management of kidney transplantation (KT), early renal graft injury (eRGI) remains a critical problem with serious impairment of graft function as well as short- and long-term outcome. Serial monitoring of peripheral blood innate immune cells might be a useful tool in predicting post-transplant eRGI and graft outcome after KT. Methods: In this prospective study, medical data of 50 consecutive patients undergoing KT at the University Hospital of Leipzig were analyzed starting at the day of KT until day 10 after the transplantation. The main outcome parameter was the occurrence of eRGI and other outcome parameters associated with graft function/outcome. eRGI was defined as graft-related complications and clinical signs of renal IRI (ischemia reperfusion injury), such as acute tubular necrosis (ATN), delayed graft function (DGF), initial nonfunction (INF) and graft rejection within 3 months following KT. Typical innate immune cells including neutrophils, natural killer (NK) cells, monocytes, basophils and dendritic cells (myeloid, plasmacytoid) were measured in all patients in peripheral blood at day 0, 1, 3, 7 and 10 after the transplantation. Receiver operating characteristics (ROC) curves were performed to assess their predictive value for eRGI. Cutoff levels were calculated with the Youden index. Significant diagnostic immunological cutoffs and other prognostic clinical factors were tested in a multivariate logistic regression model. Results: Of the 50 included patients, 23 patients developed eRGI. Mean levels of neutrophils and monocytes were significantly higher on most days in the eRGI group compared to the non-eRGI group after transplantation, whereas a significant decrease in NK cell count, basophil levels and DC counts could be found between baseline and postoperative course. ROC analysis indicated that monocytes levels on POD 7 (AUC: 0.91) and NK cell levels on POD 7 (AUC: 0.92) were highly predictive for eRGI after KT. Multivariable analysis identified recipient age (OR 1.53 (95% CI: 1.003−2.350), p = 0.040), recipient body mass index > 25 kg/m2 (OR 5.6 (95% CI: 1.36−23.9), p = 0.015), recipient cardiovascular disease (OR 8.17 (95% CI: 1.28−52.16), p = 0.026), donor age (OR 1.068 (95% CI: 1.011−1.128), p = 0.027), <0.010), deceased-donor transplantation (OR 2.18 (95% CI: 1.091−4.112), p = 0.027) and cold ischemia time (CIT) of the renal graft (OR 1.005 (95% CI: 1.001−1.01), p = 0.019) as clinically relevant prognostic factors associated with increased eRGI following KT. Further, neutrophils > 9.4 × 103/μL on POD 7 (OR 16.1 (95% CI: 1.31−195.6), p = 0.031), monocytes > 1150 cells/ul on POD 7 (OR 7.81 (95% CI: 1.97−63.18), p = 0.048), NK cells < 125 cells/μL on POD 3 (OR 6.97 (95% CI: 3.81−12.7), p < 0.01), basophils < 18.1 cells/μL on POD 10 (OR 3.45 (95% CI: 1.37−12.3), p = 0.02) and mDC < 4.7 cells/μL on POD 7 (OR 11.68 (95% CI: 1.85−73.4), p < 0.01) were revealed as independent biochemical predictive variables for eRGI after KT. Conclusions: We show that the combined measurement of immunological innate variables (NK cells and monocytes on POD 7) and specific clinical factors such as prolonged CIT, increased donor and recipient age and morbidity together with deceased-donor transplantation were significant and specific predictors of eRGI following KT. We suggest that intensified monitoring of these parameters might be a helpful clinical tool in identifying patients at a higher risk of postoperative complication after KT and may therefore help to detect and—by diligent clinical management—even prevent deteriorated outcome due to IRI and eRGI after KT.

Urinary interleukin-6 is a potentially useful diagnostic and prognostic marker of acute kidney injury in dogs

BACKGROUND

Interleukin-6 (IL6) is a pro-inflammatory cytokine implicated in the pathophysiology of urinary tract diseases. The objective of this study was to evaluate the diagnostic and prognostic utilities of urinary IL6 (uIL6) in dogs with acute kidney injury (AKI) and other urinary tract diseases.

METHODS

Eighty client-owned dogs were included and divided into four groups: AKI, chronic kidney disease (CKD), urinary tract infection and healthy controls. Urine samples were analysed for uIL6 and normalised to urinary creatinine (uIL6/uCr).

RESULTS

Dogs in the AKI group had higher uIL6/uCr compared with the control and CKD groups (p < 0.001 and 0.012, respectively). Receiver operator characteristic (ROC) curve analysis of uIL6/uCr as a diagnostic marker for AKI had an area under the curve (AUC) of 0.91 (95% confidence interval [CI], 0.81-1.0) with 82% sensitivity and 90% specificity (cutoff point 4.5 pg/mg) when including the AKI and control groups. ROC analysis including AKI compared with all other groups had an AUC of 0.77 (95% CI, 0.67-0.87) for the diagnosis of AKI with sensitivity and specificity of 71% and 78%, respectively (cutoff point 10.4 pg/mg). The 30-day mortality of the AKI group was 34%, and there was no difference in uIL6/uCr between survivors and non-survivors of AKI.

CONCLUSIONS

uIL6/uCr is a potentially sensitive and specific diagnostic marker for AKI in dogs.

Inhibition of the IRE1/JNK pathway in renal tubular epithelial cells attenuates ferroptosis in acute kidney injury

Backgroud: Ferroptosis is a form of regulated cell death in ischemia-reperfusion (I/R) injury models. Acute kidney injury (AKI) induced by I/R injury can result in cell death, and subcellular structural changes, including expansion of the endoplasmic reticulum (ER), mitochondrial shrinkage, and other morphological changes. Inositol requiring enzyme 1 (IRE1) a proximal ER stress sensor, activates c-Jun NH2-terminal kinases (JNK) in response to ER stress, which is inextricably linked to ER.

Method: To determine the resulting damage and relationship between ferroptosis and the IRE1/JNK pathway in AKI, we modeled AKI in I/R renal injury mice and hypoxia/reoxygenation (H/R) HK-2 cells, as in vivo and in vitro experiments, respectively.

Results: In I/R renal injury mice, we found that abnormal renal function; damage of renal tubular epithelial cells; activation of the IRE1/JNK pathway and ferroptosis. Our in vitro study showed a large number of reactive oxygen species and more ferroptotic mitochondria in H/R HK-2 cells. By inhibiting IRE1/JNK in I/R renal injury mice, we observed decreased blood urea nitrogen, creatinine, and tissue injury, compared with the I/R group, we also found the markers of ferroptosis changed, including decreased 4-hydroxynonenal and increased glutathione peroxidase 4, as well as in H/R induced IRE1/JNK knock-down HK-2 cell lines (stable depletion). Furthermore, inhibition of ferroptosis could also attenuate the IRE1/JNK pathway in mice following I/R and HK-2 cells following H/R.

Conclusion: We observed cross-talk between the IRE1/JNK pathway and ferroptosis in I/R or H/R induced AKI. Our findings suggest that ferroptosis plays an important role in I/R induced AKI, and that inhibition of the IRE1/JNK pathway can protect against I/R induced renal injury by inhibiting ferroptosis. The inhibition of the IRE1/JNK pathway could therefore be a feasible therapeutic target for treatment of AKI.

Ceria nanoparticles prophylactic used for renal ischemia-reperfusion injury treatment by attenuating oxidative stress and inflammatory response

Renal ischemia-reperfusion (IR) injury (RIRI) is the leading cause of acute kidney injury (AKI), a common disease with high morbidity and mortality. However, due to the lack of effective diagnostic and therapeutic tools, patients have to resort to conservative treatment. To address this issue, we have developed a novel prophylactic strategy that involves the pre-treatment use of ceria nanoparticles (CNPs) before surgery. Based on our careful study of the three different sizes of CNPs that we synthesized, 46 nm (NP46), 81 nm (NP81), and 118 nm (NP118), we have found that NP118 can be used as effective prophylactic agents against RIRI and subsequent renal fibrosis. In our experiments, the CNPs exhibited excellent antioxidant and anti-inflammatory activities in vitro and effectively protected the kidney against RIRI and renal fibrosis in vivo, as proved by the decreases in renal lesions, serum creatinine, blood urea nitrogen, apoptotic cell, KIM-1 expression, and fibrotic area in CNPs treated samples relative to RIRI group. Mechanistically, not only did the CNPs reduce oxidative stress by regulating the Nrf2 pathway, but they also attenuated RIRI induced inflammatory response by decreasing macrophage infiltration and polarization to M1 phenotype, and reducing pro-inflammatory cytokine and chemokine production. In vitro results further confirmed that CNPs pre-treatment not only dramatically decreased intracellular ROS production in renal tubular epithelial cells and vascular endothelial cells, but also effectively attenuated lipopolysaccharide-induced inflammation in RAW264.7 cells. In addition, we found that one fourth of the NP118 persisted for more than 21 days in IR kidneys, and that out of the three sizes of CNPs, NP118 achieved the best results in all our experiments. Our study provides new insights into the usage and majorization of CNPs as a potential therapy to treat or prevent RIRI and renal fibrosis.

Protective effect of saxagliptin against renal ischaemia reperfusion injury in rats

Saxagliptin is an effective and selective dipeptidyl peptidase-4 (DPP-4) inhibitor. This study was designed to determine possible protective effects of saxagliptin against damage caused by renal ischaemia/reperfusion (I/R) in rats. In this study, 40 rats were divided into 4 groups (n = 10 for each). Group 1 (Control), Group 2 (I/R) in both kidneys ischaemia of 45 min was performed, and then reperfusion was applied for 24 h. Saxagliptin (Group 3: 2 mg/kg and Group 4: 10 mg/kg) was administered by oral gavage to the animals in treatment groups, before the I/R. Saxagliptin decreased the markers (BUN, Cre, NGAL, KIM-1 and IL-18) of acute renal damage in blood and kidney tissue. Saxagliptin provided increase in antioxidant enzyme levels and decrease in MDA and apoptosis. Histological results showed that the administration of saxagliptin exhibited a protective effect against renal damage caused by I/R. These results indicates that saxagliptin provide protection against kidney injury caused by I/R.

Renal Injuries after Cardiac Arrest: A Morphological Ultrastructural Study

BACKGROUND

This study aims to investigate the probable lesions and injuries induced in the renal tissue after a cardiac arrest. The renal ischemia-reperfusion model in cardiac arrest describes the effects of ischemia in the kidneys, alongside a whole-body ischemia-reperfusion injury. This protocol excludes ischemic conditions caused by surgical vascular manipulation, venous injury or venous congestion.

METHODS

For the experimental study, 24 swine were subjected to cardiac arrest. Seven minutes later, the cardiopulmonary resuscitation technique was performed for 5 min. Afterwards, advanced life support was provided. The resuscitated swine consisted one group and the non-resuscitated the other. Tissue samples were obtained from both groups for light and electron microscopy evaluation.

RESULTS

Tissue lesions were observed in the tubules, parallel to destruction of the microvilli, reduction in the basal membrane invaginations, enlarged mitochondria, cellular vacuolization, cellular apoptosis and disorganization. In addition, fusion of the podocytes, destruction of the Bowman's capsule parietal epithelium and abnormal peripheral urinary space was observed. The damage appeared more extensive in the non-resuscitated swine group.

CONCLUSIONS

Acute kidney injury is not the leading cause of death after cardiac arrest. However, evidence suggests that the kidney damage after a cardiac arrest should be highly considered in the prognosis of the patients' health outcome.

IRE1α Inhibitors as a Promising Therapeutic Strategy in Blood Malignancies

Synthesis, folding, and structural maturation of proteins occur in the endoplasmic reticulum (ER). Accumulation of misfolded or unfolded proteins in the ER lumen contributes to the induction of ER stress and activation of the unfolded protein response (UPR) signaling pathway. Under ER stress, the UPR tries to maintain cellular homeostasis through different pathways, including the inositol-requiring enzyme 1 alpha (IRE1α)-dependent ones. IRE1α is located in an ER membrane, and it is evolutionarily the oldest UPR sensor. Activation of IRE1α via ER stress triggers the formation of the spliced form of XBP1 (XBP1s), which has been linked to a pro-survival effect in cancer cells. The role of IRE1α is critical for blood cancer cells, and it was found that the levels of IRE1α and XBP1s are elevated in various hematological malignancies. This review paper is focused on summarizing the latest knowledge about the role of IRE1α and on the assessment of the potential utility of IRE1α inhibitors in blood cancers.

Study of Renal Accumulation of Targeted Polycations in Acute Kidney Injury

Acute kidney injury (AKI) is a global healthcare burden characterized by rapid loss of renal function and high morbidity and mortality. Chemokine receptor CXCR4 participates in the renal infiltration of immune cells following injury and in local inflammatory enhancement. Injured renal tubule cells overexpress CXCR4, which could be used as a target for improved drug delivery in AKI. Plerixafor is a small-molecule CXCR4 antagonist that has shown beneficial effects against AKI and has been previously developed into a polymeric analog (polymeric plerixafor, PP). With the goal of gaining a better understanding of how overall charge and hydrophilicity affect renal accumulation of PP, we have synthesized PP copolymers containing hydroxyl, carboxyl, primary amine, and alkyl moieties using Michael-type addition copolymerization. All synthesized copolymers showed excellent CXCR4-binding and inhibiting ability in vitro and improved cellular uptake in hypoxia-reoxygenation stimulated mouse tubule cells. Analysis of serum protein binding revealed that polymers with hydroxyl group modification showed the least amount of protein binding. Biodistribution of the polymers was tested in a unilateral ischemia reperfusion-induced AKI mouse model. The results showed significant differences in accumulation in the injured kidneys depending on the net charge and hydrophilicity of the polymers. The findings of this study will guide the development of polymeric drug carriers for targeted delivery to injured kidneys for better AKI therapy.

Therapeutic role of uterine-derived stem cells in acute kidney injury

BACKGROUND

Acute kidney injury (AKI) causes abrupt deterioration in kidney function that disrupts metabolic, electrolyte and fluid homeostasis. Although the prevalence of AKI is steadily increasing, no definitive treatment options are available, leading to severe morbidity and mortality. We evaluated the role of uterine-derived multipotent stem cells in kidney regeneration after ischemic AKI.

METHODS

Female C57BL/6J mice were hysterectomized and subsequently subject to AKI by either unilateral or bilateral renal ischemia-reperfusion injury. Uterine-derived cells (UDCs), containing a population of uterine stem cells, were isolated from the uteri of female transgenic DsRed mice and injected intravenously to AKI mice. Engraftment of DsRed cells was analyzed by flow cytometry while serum creatinine levels were determined colorimetrically. Expression of UDC markers and cytokine markers were analyzed by immunohistochemical and qRT-PCR methods, respectively. The Kaplan-Meier method was used to analyze survival time while unpaired t test with Welch's correction used for data analysis between two groups.

RESULTS

Mice with an intact uterus, and hence an endogenous source of UDCs, had a higher survival rate after bilateral ischemic AKI compared to hysterectomized mice. Mice treated with infusion of exogenous UDCs after hysterectomy/AKI had lower serum creatinine levels and higher survival rates compared to controls that did not receive UDCs. Engraftment of labeled UDCs was significantly higher in kidneys of bilateral ischemic AKI mice compared to those that underwent a sham surgery. When unilateral ischemic AKI was induced, higher numbers of UDCs were found in the injured than non-injured kidney. Immunofluorescence staining demonstrated double-positive DsRed/Lotus tetragonolobus agglutinin (LTA) positive cells and DsRed/CD31 positive cells indicating contribution of UDCs in renal tubular and vascular regeneration. Expression of Cxcl12, Bmp2, Bmp4, and Ctnf in renal tissue was significantly higher in the UDCs injection group than the control group.

CONCLUSIONS

UDCs engrafted injured kidneys, contributed to proximal tubule and vascular regeneration, improved kidney function and increased survival in AKI mice. UDC administration is a promising new therapy for AKI. Endogenous uterine stem cells likely also preserve kidney function, suggesting a novel interaction between the uterus and kidney. We suggest that hysterectomy may have a detrimental effect on response to renal injury.

The molecular chaperone GRP170 protects against ER stress and acute kidney injury in mice

Molecular chaperones are responsible for maintaining cellular homeostasis, and one such chaperone, GRP170, is an endoplasmic reticulum (ER) resident that oversees both protein biogenesis and quality control. We previously discovered that GRP170 regulates the degradation and assembly of the epithelial sodium channel (ENaC), which reabsorbs sodium in the distal nephron and thereby regulates salt-water homeostasis and blood pressure. To define the role of GRP170 - and, more generally, molecular chaperones in kidney physiology - we developed an inducible, nephron-specific GRP170-KO mouse. Here, we show that GRP170 deficiency causes a dramatic phenotype: profound hypovolemia, hyperaldosteronemia, and dysregulation of ion homeostasis, all of which are associated with the loss of ENaC. Additionally, the GRP170-KO mouse exhibits hallmarks of acute kidney injury (AKI). We further demonstrate that the unfolded protein response (UPR) is activated in the GRP170-deficient mouse. Notably, the UPR is also activated in AKI when originating from various other etiologies, including ischemia, sepsis, glomerulonephritis, nephrotic syndrome, and transplant rejection. Our work establishes the central role of GRP170 in kidney homeostasis and directly links molecular chaperone function to kidney injury.

The Interaction of Central Nervous System and Acute Kidney Injury: Pathophysiology and Clinical Perspectives

Acute kidney injury (AKI) is a common disorder in critically ill hospitalized patients. Its main pathological feature is the activation of the sympathetic nervous system and the renin-angiotensin system (RAS). This disease shows a high fatality rate. The reason is that only renal replacement therapy and supportive care can reduce the impact of the disease, but those measures cannot significantly improve the mortality. This review focused on a generalization of the interaction between acute kidney injury and the central nervous system (CNS). It was found that the CNS further contributes to kidney injury by regulating sympathetic outflow and oxidative stress in response to activation of the RAS and increased pro-inflammatory factors. Experimental studies suggested that inhibiting sympathetic activity and RAS activation in the CNS and blocking oxidative stress could effectively reduce the damage caused by AKI. Therefore, it is of significant interest to specify the mechanism on how the CNS affects AKI, as we could use such mechanism as a target for clinical interventions to further reduce the mortality and improve the complications of AKI.

Systematic Review Registration: [www.ClinicalTrials.gov], identifier [registration number].

Role of TRPC6 in kidney damage after acute ischemic kidney injury

Transient receptor potential channel subfamily C, member 6 (TRPC6), a non-selective cation channel that controls influx of Ca²⁺ and other monovalent cations into cells, is widely expressed in the kidney. TRPC6 gene variations have been linked to chronic kidney disease but its role in acute kidney injury (AKI) is unknown. Here we aimed to investigate the putative role of TRPC6 channels in AKI. We used Trpc6^-/- mice and pharmacological blockade (SH045 and BI-749327), to evaluate short-term AKI outcomes. Here, we demonstrate that neither Trpc6 deficiency nor pharmacological inhibition of TRPC6 influences the short-term outcomes of AKI. Serum markers, renal expression of epithelial damage markers, tubular injury, and renal inflammatory response assessed by the histological analysis were similar in wild-type mice compared to Trpc6^-/- mice as well as in vehicle-treated versus SH045- or BI-749327-treated mice. In addition, we also found no effect of TRPC6 modulation on renal arterial myogenic tone by using blockers to perfuse isolated kidneys. Therefore, we conclude that TRPC6 does not play a role in the acute phase of AKI. Our results may have clinical implications for safety and health of humans with TRPC6 gene variations, with respect to mutated TRPC6 channels in the response of the kidney to acute ischemic stimuli.

Therapeutic effects of apocynin on ovarian ischemia-reperfusion induced lung injury

Ovarian ischemia-reperfusion (I-R) injury may damage remote organs, including the lungs. We investigated whether apocynin, a NADPH oxidase inhibitor, might protect against ovarian I-R induced apoptosis in the lungs of rats. Bilateral ovarian I-R was induced for 3 h, then apocynin was applied at two concentrations. Lung tissue was evaluated using spectrophotometric and immunohistochemical methods. We found that I-R increased total oxidant status (TOS), oxidative stress index (OSI) and myeloperoxidase (MPO) levels, and immunostaining of nuclear factor kappa-B (NF-κB), light chain 3B (LC3B), interleukin 1-beta (IL-1β), caspase-3 and tumor necrosis factor-alpha (TNF-α), but decreased superoxide dismutase (SOD) values. Apocynin application to I-R injured rats enhanced recovery of lung tissue oxidants and improved both histology and frequency of apoptosis.

Involvement of Inflammasome Components in Kidney Disease

Inflammasomes are multiprotein complexes with an important role in the innate immune response. Canonical activation of inflammasomes results in caspase-1 activation and maturation of cytokines interleukin-1β and -18. These cytokines can elicit their effects through receptor activation, both locally within a certain tissue and systemically. Animal models of kidney diseases have shown inflammasome involvement in inflammation, pyroptosis and fibrosis. In particular, the inflammasome component nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) and related canonical mechanisms have been investigated. However, it has become increasingly clear that other inflammasome components are also of importance in kidney disease. Moreover, it is becoming obvious that the range of molecular interaction partners of inflammasome components in kidney diseases is wide. This review provides insights into these current areas of research, with special emphasis on the interaction of inflammasome components and redox signalling, endoplasmic reticulum stress, and mitochondrial function. We present our findings separately for acute kidney injury and chronic kidney disease. As we strictly divided the results into preclinical and clinical data, this review enables comparison of results from those complementary research specialities. However, it also reveals that knowledge gaps exist, especially in clinical acute kidney injury inflammasome research. Furthermore, patient comorbidities and treatments seem important drivers of inflammasome component alterations in human kidney disease.