Cytokines induce small intestine and liver injury after renal ischemia or nephrectomy

Lymphocytes and innate immune cells in acute kidney injury and repair

Acute kidney injury (AKI) is a common and serious disease entity that affects native kidneys and allografts but for which no specific treatments exist. Complex intrarenal inflammatory processes driven by lymphocytes and innate immune cells have key roles in the development and progression of AKI. Many studies have focused on prevention of early injury in AKI. However, most patients with AKI present after injury is already established. Increasing research is therefore focusing on mechanisms of renal repair following AKI and prevention of progression from AKI to chronic kidney disease. CD4+ and CD8+ T cells, B cells and neutrophils are probably involved in the development and progression of AKI, whereas regulatory T cells, double-negative T cells and type 2 innate lymphoid cells have protective roles. Several immune cells, such as macrophages and natural killer T cells, can have both deleterious and protective effects, depending on their subtype and/or the stage of AKI. The immune system not only participates in injury and repair processes during AKI but also has a role in mediating AKI-induced distant organ dysfunction. Targeted manipulation of immune cells is a promising therapeutic strategy to improve AKI outcomes.

Kidney ischemia/reperfusion injury causes cholangiocytes primary cilia disruption and abnormal bile secretion

BACKGROUND

Acute kidney injury (AKI) causes distant liver injury, to date, which causes poor outcomes of patients with AKI. Many studies have been performed to overcome AKI-associated liver injury. However, those studies have mainly focused on hepatocytes, and AKI-induced liver injury still remains a clinical problem. Here, we investigated the implication of cholangiocytes and their primary cilia which are critical in final bile secretion. Cholangiocyte, a lining cell of bile ducts, are the only liver epithelial cell containing primary cilium (a microtubule-based cell surface signal-sensing organelle).

METHODS

Cystathione γ-lyase (CSE, a transsulfuration enzyme) deficient and wild-type mice were subjected to kidney ischemia followed by reperfusion (KIR). Some mice were administered with N-acetyl-cysteine (NAC).

RESULTS

KIR damaged hepatocytes and cholagiocytes, disrupted cholangiocytes primary cilia, released the disrupted ciliary fragments into the bile, and caused abnormal bile secretion. Glutathione (GSH) and H2S levels in the livers were significantly reduced by KIR, resulting in increased the ratio oxidized GSH to total GSH, and oxidation of tissue and bile. CSE and cystathione β-synthase (CBS) expression were lowered in the liver after KIR. NAC administration increased total GSH and H2S levels in the liver and attenuated KIR-induced liver injuries. In contrast, Cse deletion caused the reduction of total GSH levels and worsened KIR-induced liver injuries, including primary cilia damage and abnormal bile secretion.

CONCLUSIONS

These results indicate that KIR causes cholangiocyte damage, cholangiocytes primary cilia disruption, and abnormal bile secretion through reduced antioxidative ability of the liver.

Disruption in glutathione metabolism and altered energy production in the liver and kidney after ischemic acute kidney injury in mice

Acute kidney injury (AKI) is a systemic disease that affects energy metabolism in various remote organs in murine models of ischemic AKI. However, AKI-mediated effects in the liver have not been comprehensively assessed. After inducing ischemic AKI in 8-10-week-old, male C57BL/6 mice, mass spectrometry metabolomics revealed that the liver had the most distinct phenotype 24 h after AKI versus 4 h and 7 days. Follow up studies with in vivo [13C6]-glucose tracing on liver and kidney 24 h after AKI revealed 4 major findings: (1) increased flux through glycolysis and the tricarboxylic (TCA) cycle in both kidney and liver; (2) depleted hepatic glutathione levels and its intermediates despite unchanged level of reactive oxygen species, suggesting glutathione consumption exceeds production due to systemic oxidative stress after AKI; (3) hepatic ATP depletion despite unchanged rate of mitochondrial respiration, suggesting increased ATP consumption relative to production; (4) increased hepatic and renal urea cycle intermediates suggesting hypercatabolism and upregulation of the urea cycle independent of impaired renal clearance of nitrogenous waste. Taken together, this is the first study to describe the hepatic metabolome after ischemic AKI in a murine model and demonstrates that there is significant liver-kidney crosstalk after AKI.

Incidence, risk factors, and outcomes of acute liver injury in hospitalized adults with acute kidney injury: a large multicenter study

BACKGROUND

Acute kidney injury (AKI) and acute liver injury (ALI) were associated with poor outcomes during hospitalization, respectively. However, the clinical outcome of AKI combined with ALI (AKI-ALI) remains unknown. The current study aimed to describe AKI-ALI's incidences, risk factors, and outcomes.

METHODS

The study population included patients aged 18-99 years with enough serum creatinine and liver testing hospitalized at 19 medical centers throughout China between 2000 and 2021. AKI was defined by Kidney Disease Improving Global Outcomes and ALI was defined by the change of liver enzymes based on Asia Pacific Association of Study of Liver consensus guidelines. Cox proportional hazard model was used to identify risk factors for AKI-ALI, and a time-dependent Cox proportional hazard regression model was used to estimate the association between AKI-ALI and in-hospital mortality.

RESULTS

Among the 18,461 patients with AKI, 1689 (9.1%) combined with ALI. Male patients or those who have used nonsteroidal anti-inflammatory drugs or vasopressors, and who have heart failure or shock, with higher AST or GGT values, were associated with an increased risk of AKI-ALI. Compared with AKI-nonALI, patients with AKI-ALI were at higher risk of in-hospitalized mortality (hazard ratio [HR] 1.76, 95% confidence interval [CI] 1.54, 2.00). In addition, a stronger association between AKI-ALI and in-hospital mortality was found in those with lower AKI grades (p for interaction = 0.037).

CONCLUSIONS

ALI was not uncommon among patients with AKI, especially in patients who used vasopressors and had shock. This study highlights the association between AKI-ALI and a significantly increased risk of mortality. It suggests that dynamic monitoring of liver function is essential, particularly in patients with AST and GGT exceeding the normal upper limit, to improve the in-hospital prognosis of AKI patients.

Interorgan communication networks in the kidney-lung axis

The homeostasis and health of an organism depend on the coordinated interaction of specialized organs, which is regulated by interorgan communication networks of circulating soluble molecules and neuronal connections. Many diseases that seemingly affect one primary organ are really multiorgan diseases, with substantial secondary remote organ complications that underlie a large part of their morbidity and mortality. Acute kidney injury (AKI) frequently occurs in critically ill patients with multiorgan failure and is associated with high mortality, particularly when it occurs together with respiratory failure. Inflammatory lung lesions in patients with kidney failure that could be distinguished from pulmonary oedema due to volume overload were first reported in the 1930s, but have been largely overlooked in clinical settings. A series of studies over the past two decades have elucidated acute and chronic kidney-lung and lung-kidney interorgan communication networks involving various circulating inflammatory cytokines and chemokines, metabolites, uraemic toxins, immune cells and neuro-immune pathways. Further investigations are warranted to understand these clinical entities of high morbidity and mortality, and to develop effective treatments.

Review on Kidney-Liver Crosstalk: Pathophysiology of Their Disorders

Kidney-liver crosstalk plays a crucial role in normal and certain pathological conditions. In pathologic states, both renal-induced liver damage and liver-induced kidney diseases may happen through these kidney-liver interactions. This bidirectional crosstalk takes place through the systemic conditions that mutually influence both the liver and kidneys. Ischemia and reperfusion, cytokine release and pro-inflammatory signaling pathways, metabolic acidosis, oxidative stress, and altered enzyme activity and metabolic pathways establish the base of this interaction between the kidneys and liver. In these concomitant kidney-liver diseases, the survival rates strongly correlate with early intervention and treatment of organ dysfunction. Proper care of a nephrologist and hepatologist and the identification of pathological conditions using biomarkers at early stages are necessary to prevent the complications induced by this complex and potentially vicious cycle. Therefore, understanding the characteristics of this crosstalk is essential for better management. In this review, we discussed the available literature concerning the detrimental effects of kidney failure on liver functions and liver-induced kidney diseases.

Postoperative decline in renal function after rectal resection and all-cause mortality: a retrospective cohort study

AIM

Fluid loss, dehydration and resultant kidney injury are common when a diverting ileostomy is formed during rectal cancer surgery, the consequences of which are unknown. The aim of this retrospective single-site cohort study is to evaluate the impact of sustained postoperative renal dysfunction after rectal resection on long-term renal impairment and survival.

METHOD

All patients with rectal adenocarcinoma undergoing resection between January 2003 and March 2017 were included, with follow-up to June 2020. The primary outcome was impact on long-term mortality attributed to a 25% or greater drop in estimated glomerular filtration rate (eGFR) following rectal resection. Secondary outcomes were the long-term effect on renal function resulting from the same drop in eGFR and the effect on long-term mortality and renal function of a 50% drop in eGFR. We also calculated the effect on mortality of a 1% drop in eGFR.

RESULTS

A total of 1159 patients were identified. Postoperative reductions in eGFR of 25% and 50% were associated with long-term overall mortality with adjusted hazard ratios of 1.84 (1.22-2.77) (p = 0.004) and 2.88 (1.45-5.71) (p = 0.002). The median survival of these groups was 86.0 (64.0-108.0) months and 53.3 (7.8-98.8) months compared with 144.5 (128.1-160.9) months for controls. Long-term effects on renal function were demonstrated, with those who sustained a >25% drop in renal function having a 38.8% mean decline in eGFR at 10 years compared with 10.2% in controls.

CONCLUSION

Persistent postoperative declines in renal function may be linked to long-term mortality. Further research is needed to assess causal relationships and prevention.

Impaired microvascular circulation in distant organs following renal ischemia

Mortality in acute kidney injury (AKI) patients remains very high, although very important advances in understanding the pathophysiology and in diagnosis and supportive care have been made. Most commonly, adverse outcomes are related to extra-renal organ dysfunction and failure. We and others have documented inflammation in remote organs as well as microvascular dysfunction in the kidney after renal ischemia. We hypothesized that abnormal microvascular flow in AKI extends to distant organs. To test this hypothesis, we employed intravital multiphoton fluorescence imaging in a well-characterized rat model of renal ischemia/reperfusion. Marked abnormalities in microvascular flow were seen in every organ evaluated, with decreases up to 46% observed 48 hours postischemia (as compared to sham surgery, p = 0.002). Decreased microvascular plasma flow was found in areas of erythrocyte aggregation and leukocyte adherence to endothelia. Intravital microscopy allowed the characterization of the erythrocyte formations as rouleaux that flowed as one-dimensional aggregates. Observed microvascular abnormalities were associated with significantly elevated fibrinogen levels. Plasma flow within capillaries as well as microthrombi, but not adherent leukocytes, were significantly improved by treatment with the platelet aggregation inhibitor dipyridamole. These microvascular defects may, in part, explain known distant organ dysfunction associated with renal ischemia. The results of these studies are relevant to human acute kidney injury.

Acute kidney injury and distant organ dysfunction-network system analysis

Acute kidney injury (AKI) occurs in about half of critically ill patients and associates with high in-hospital mortality, increased long-term mortality post-discharge and subsequent progression to chronic kidney disease. Numerous clinical studies have shown that AKI is often complicated by dysfunction of distant organs, which is a cause of the high mortality associated with AKI. Experimental studies have elucidated many mechanisms of AKI-induced distant organ injury, which include inflammatory cytokines, oxidative stress and immune responses. This review will provide an update on evidence of organ crosstalk and potential therapeutics for AKI-induced organ injuries, and present the new concept of a systemic organ network to balance homeostasis and inflammation that goes beyond kidney-crosstalk with a single distant organ.

Prazosin Protects the Liver Against Renal Ischemia/Reperfusion Injury in Rats

Acute kidney injury (AKI) is a common subsequent problem after many medical conditions. AKI is associated with distant organ dysfunction where systemic inflammation and oxidative stress play major roles. In this study, the effect of Prazosin, an α1-Adrenergic receptor antagonist, was investigated on the liver injury induced by kidney ischemia-reperfusion (I/R) in rats. Male adult Wistar rats (n=21) were divided into three groups: sham, kidney I/R, and kidney I/R pre-treated with Prazosin (1 mg/kg). Kidney I/R was induced by vascular clamping of the left kidney for 45 min to reduce the blood flow. Oxidative and antioxidant factors along with apoptotic (Bax, Bcl-2, caspase3), and inflammatory (NF-κβ, IL-1β, and IL-6) factors were measured in the liver at protein levels. Prazosin could reserve liver function (p<0.01) and increase glutathione level (p<0.05) after kidney I/R significantly. Malonil dialdehyde (MDA), a lipid peroxidation marker, was diminished more significantly in Prazosin-treated rats compared to the kidney I/R group (p<0.001). Inflammatory and apoptotic factors were diminished by Prazosin pre-treatment in the liver tissue (p<0.05). Pre-administration of Prazosin could preserve liver function and decrease its inflammatory and apoptotic factors under kidney I/R conditions.

Risk and Timing of De Novo Sepsis in Critically Ill Children after Acute Kidney Injury

Key Points

Critically ill children who developed AKI have a 42% increase in the probability of developing subsequent hospital-acquired sepsis when compared with children without AKI. When evaluating risk of sepsis over time, children with stage 3 AKI remain at increased risk for sepsis for at least 2 weeks after AKI onset. Medical providers should monitor for signs of sepsis after AKI and limit exposures that may increase the risk for infection.

Background

AKI is common among critically ill children and is associated with an increased risk for de novo infection; however, little is known about the epidemiology and temporal relationship between AKI and AKI-associated infection in this cohort.

Methods

We conducted a single-center retrospective cohort study of children admitted to the pediatric and cardiac intensive care units (ICUs) at a tertiary pediatric care center. The relationship between nonseptic AKI and the development of hospital-acquired sepsis was assessed using Cox proportional hazards models using AKI as a time-varying covariate.

Results

Among the 5695 children included in this study, AKI occurred in 20.2% from ICU admission through 30 days. Hospital-acquired sepsis occurred twice as often among children with AKI compared with those without AKI (10.1% versus 4.6%) with an adjusted hazard ratio of 1.42 (95% confidence interval, 1.12 to 1.81). Among the 117 children who developed sepsis after AKI, 80.3% developed sepsis within 7 days and 96.6% within 14 days of AKI onset, with a median time from AKI onset to sepsis of 2.6 days (interquartile range, 1.5–4.7). When assessing change in risk over time, the hazard rate for sepsis remained elevated for children with stage 3 AKI compared with children without AKI at 13.5 days after AKI onset, after which the estimation of hazard rates was limited by the number of children remaining in the hospital.

Conclusions

AKI is an independent risk factor for de novo sepsis. Critically ill children with stage 3 AKI remain at increased risk for sepsis at 13.5 days after AKI onset.

Mineralocorticoid Receptor Antagonism Attenuates Multiple Organ Failure after Renal Ischemia and Reperfusion in Mice

Renal ischemia reperfusion (IR) injury is a major cause of acute kidney injury (AKI) that is often complicated by multiple organ failure of the liver and intestine. The mineralocorticoid receptor (MR) is activated in patients with renal failure associated with glomerular and tubular damage. We thus investigated whether canrenoic acid (CA), a mineralocorticoid receptor (MR) antagonist, protects against AKI-induced hepatic and intestinal injury, suggesting the underlying mechanisms. Mice were divided into five groups: sham mice, mice subjected to renal IR, and mice pretreated with canrenoic acid (CA; 1 or 10 mg/kg) 30 min prior to renal IR. At 24 h after renal IR, the levels of plasma creatinine, alanine aminotransferase and aldosterone were measured, and structural changes and inflammatory responses of the kidney, liver, and intestine were analyzed. We found that CA treatment reduced plasma creatinine levels, tubular cell death and oxidative stress induced by renal IR. CA treatment also decreased renal neutrophil infiltration and inflammatory cytokine expression and inhibited the release of high-mobility group box 1 induced by renal IR. Consistently, CA treatment reduced renal IR-induced plasma alanine transaminase, hepatocellular injury and neutrophil infiltration, and inflammatory cytokine expression. CA treatment also decreased small intestinal cell death, neutrophil infiltration and inflammatory cytokine expression induced by renal IR. Taken together, we conclude that MR antagonism by CA treatment protects against multiple organ failure in the liver and intestine after renal IR.

Therapeutic propensity of ginsenosides Rg1 and Rg3 in rhabdomyolysis-induced acute kidney injury and renohepatic crosstalk in rats

BACKGROUND

Ginseng is a traditional herbal medicine used for thousands of years in Southeast Asian countries because of its medicinal properties. Ginsenosides Rg1 and Rg3 have demonstrated therapeutic properties against a broad spectrum of diseases.

PURPOSE

Here in this study, we investigated the therapeutic efficacy of Rg1 and Rg3 in alleviating glycerol-induced acute kidney injury, also known as rhabdomyolysis-induced acute kidney injury (RAKI).

METHODS

AKI was induced in male Wistar rats through intramuscular injection of 10 mL/kg glycerol and simultaneous oral treatment of ginsenosides Rg1 and Rg3 for 3 days. We also evaluated the therapeutic potential of Rg1 and Rg3 on human embryonic kidney epithelial (HEK-293). Cell viability and LDH assay were performed on HEK-293 cells to evaluate the toxicity of Rg1 and Rg3. Evaluation of important kidney damage markers such as creatinine and blood urea nitrogen (BUN) was carried out at different time points from the rat serum. Histopathological analysis was performed on kidney tissues. We also performed experiments such as ELISA assay, immunohistochemistry, immunofluorescence staining, COMET assay, western blotting, TUNEL assay, and flow cytometry to obtain results.

RESULTS

Rg1 and Rg3 significantly downregulated the expression of kidney damage markers such as creatinine and BUN in a dose-dependent manner. Histopathological analysis revealed damage across the glomerulus, tubules, and collecting duct rendering the kidney dysfunctional in glycerol treatment groups. However, Rg1 and Rg3 treated groups showed a significant reduction in tubular necrosis at both 10 and 20 mg/kg. There was also a sharp downregulation of oxidative and ER stress markers. Additionally, we observed nuclear translocation of Nrf2 which were more prominent in kidney tissues. Rg1 and Rg3 were also able to mitigate apoptotic cell death in vitro and in vivo evaluated through immunofluorescence staining for p53, TUNEL assay, flow cytometry, and immunoblotting for intrinsic apoptosis markers.

CONCLUSION

In summary, we conclude that Rg1 and Rg3 exhibited natural therapeutic remedy against AKI.

Effect of Renal Ischemia Reperfusion on Brain Neuroinflammation

Acute kidney injury (AKI) is an inflammatory sequence. It can lead to distant organ injury, including damage to the central nervous system (CNS), mediated by increased circulating cytokines and other inflammatory mediators. It can also lead to increased blood-brain barrier (BBB) permeability. However, the effect of AKI on the inflammatory response of the brain has not yet been investigated. Therefore, we observed the effect of AKI on BBB permeability, microglia and astrocyte activation, and neuronal toxicity in the brain. The striatum and ventral midbrain, known to control overall movement, secrete the neurotransmitter dopamine. The activation of microglia and astrocytes present in this area causes neuro-degenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD). The activation of astrocytes and microglia in the hippocampus and cerebral cortex, which are responsible for important functions, including memory, learning, concentration, and language, can trigger nerve cell apoptosis. The activation of astrocytes and microglia at this site is also involved in the inflammatory response associated with the accumulation of beta-amyloid. In the situation of kidney ischemia reperfusion (IR)-induced AKI, activation of microglia and astrocytes were observed in the striatum, ventral midbrain, hippocampus, and cortex. However, neuronal cell death was not observed until 48 h.

Organ Crosstalk in Acute Kidney Injury: Evidence and Mechanisms

Acute kidney injury (AKI) is becoming a public health problem worldwide. AKI is usually considered a complication of lung, heart, liver, gut, and brain disease, but recent findings have supported that injured kidney can also cause dysfunction of other organs, suggesting organ crosstalk existence in AKI. However, the organ crosstalk in AKI and the underlying mechanisms have not been broadly reviewed or fully investigated. In this review, we summarize recent clinical and laboratory findings of organ crosstalk in AKI and highlight the related molecular mechanisms. Moreover, their crosstalk involves inflammatory and immune responses, hemodynamic change, fluid homeostasis, hormone secretion, nerve reflex regulation, uremic toxin, and oxidative stress. Our review provides important clues for the intervention for AKI and investigates important therapeutic potential from a new perspective.

Acute kidney injury-associated delirium: a review of clinical and pathophysiological mechanisms

Acute kidney injury is a known clinical risk factor for delirium, an acute cognitive dysfunction that is commonly encountered in the critically ill population. In this comprehensive review of clinical and basic research studies, we detail the epidemiology, clinical implications, pathogenesis, and management strategies of patients with acute kidney injury-associated delirium. Specifically addressed are the pathological roles of endogenous toxin or drug accumulation, acute kidney injury-mediated neuroinflammation, and acute kidney injury-associated volume overload as discrete potential biological mechanisms of the condition. The optimization of clinical contributors and normalization of renal function are reviewed as pragmatic management strategies in addition to potential and emerging therapeutic approaches.

Sepsis and Acute Kidney Injury: A Review Focusing on the Bidirectional Interplay

Although sepsis and acute kidney injury (AKI) have a bidirectional interplay, the pathophysiological mechanisms between AKI and sepsis are not clarified and worthy of a comprehensive and updated review. The primary pathophysiology of sepsis-associated AKI (SA-AKI) includes inflammatory cascade, macrovascular and microvascular dysfunction, cell cycle arrest, and apoptosis. The pathophysiology of sepsis following AKI contains fluid overload, hyperinflammatory state, immunosuppression, and infection associated with kidney replacement therapy and catheter cannulation. The preventive strategies for SA-AKI are non-specific, mainly focusing on infection control and preventing further kidney insults. On the other hand, the preventive strategies for sepsis following AKI might focus on decreasing some metabolites, cytokines, or molecules harmful to our immunity, supplementing vitamin D3 for its immunomodulation effect, and avoiding fluid overload and unnecessary catheter cannulation. To date, several limitations persistently prohibit the understanding of the bidirectional pathophysiologies. Conducting studies, such as the Kidney Precision Medicine Project, to investigate human kidney tissue and establishing parameters or scores better to determine the occurrence timing of sepsis and AKI and the definition of SA-AKI might be the prospects to unveil the mystery and improve the prognoses of AKI patients.

Crosstalk between kidney and liver in non-alcoholic fatty liver disease: mechanisms and therapeutic approaches

Liver and kidney are vital organs that maintain homeostasis and injury to either of them triggers pathogenic pathways affecting the other. For example, non-alcoholic fatty liver disease (NAFLD) promotes the progression of chronic kidney disease (CKD), vice versa acute kidney injury (AKI) endorses the induction and progression of liver dysfunction. Progress in clinical and basic research suggest a role of excessive fructose intake, insulin resistance, inflammatory cytokines production, activation of the renin-angiotensin system, redox imbalance, and their impact on epigenetic regulation of gene expression in this context. Recent developments in experimental and clinical research have identified several biochemical and molecular pathways for AKI-liver interaction, including altered liver enzymes profile, metabolic acidosis, oxidative stress, activation of inflammatory and regulated cell death pathways. This review focuses on the current preclinical and clinical findings on kidney-liver crosstalk in NAFLD-CKD and AKI-liver dysfunction settings and highlights potential molecular mechanisms and therapeutic targets.

Intestinal microbiota dysbiosis in acute kidney injury: novel insights into mechanisms and promising therapeutic strategies

In recent years, the clinical impact of intestinal microbiota–kidney interaction has been emerging. Experimental evidence highlighted a bidirectional evolutionary correlation between intestinal microbiota and kidney diseases. Nonetheless, acute kidney injury (AKI) is still a global public health concern associated with high morbidity, mortality, healthcare costs, and limited efficient therapy. Several studies on the intestinal microbiome have improved the knowledge and treatment of AKI. Therefore, the present review outlines the concept of the gut–kidney axis and data about intestinal microbiota dysbiosis in AKI to improve the understanding of the mechanisms of the intestinal microbiome on the modification of kidney function and response to kidney injury. We also introduced the future directions and research areas, emphasizing the intervention approaches and recent research advances of intestinal microbiota dysbiosis during AKI, thereby providing a new perspective for future clinical trials.

Interorgan crosstalk mechanisms in disease: the case of acute kidney injury-induced remote lung injury

Homeostasis and health of multicellular organisms with multiple organs depends on interorgan communication. Tissue injury in one organ disturbs this homeostasis and can lead to disease in multiple organs, or multiorgan failure. Many routes of interorgan crosstalk during homeostasis are relatively well known, but interorgan crosstalk in disease still lacks understanding. In particular, how tissue injury in one organ can drive injury at remote sites and trigger multiorgan failure with high mortality is poorly understood. As examples, acute kidney injury can trigger acute lung injury and cardiovascular dysfunction; pneumonia, sepsis or liver failure conversely can cause kidney failure; lung transplantation very frequently triggers acute kidney injury. Mechanistically, interorgan crosstalk after tissue injury could involve soluble mediators and their target receptors, cellular mediators, in particular immune cells, as well as newly identified neuro-immune connections. In this review, I will focus the discussion of deleterious interorgan crosstalk and its mechanistic concepts on one example, acute kidney injury-induced remote lung injury.

Early Hypertransaminasemia after Kidney Transplantation: Significance and Evolution According to Donor Type

Early hypertransaminasemia after kidney transplantation (KT) is frequent. It has been associated with the crosstalk produced between the liver and the kidney in ischemia-reperfusion situations. However, the influence of the donor type has not been evaluated. We present a retrospective study analyzing the increase in serum aspartate aminotransferase/alanine aminotransferase (AST/ALT) during the first three months post-KT in 151 recipients who received thymoglobulin as induction therapy, either from brain-death donors (DBD, n = 75), controlled circulatory death donors (cDCD, n = 33), or uncontrolled DCD (uDCD, n = 43). Eighty-five KT recipients from DBD who received basiliximab were included as controls. From KT recipients who received thymoglobulin, 33.6/43.4% presented with an increase in AST/ALT at 72 h post-KT, respectively. Regarding donor type, the percentage of recipients who experienced 72 h post-KT hypertransaminasemia was higher in uDCD group (65.1/83.7% vs. 20.3/26% in DBD and 20.7/27.6% in cDCD, p < 0.001). Within the control group, 9.4/12.9% of patients presented with AST/ALT elevation. One month after transplant, AST/ALT values returned to baseline in all groups. The multivariate analysis showed that uDCD recipients had 6- to 12-fold higher risk of developing early post-KT hypertransaminasemia. Early post-KT hypertransaminasemia is a frequent and transient event related to the kidney donor type, being more frequent in uDCD recipients.

Treprostinil alleviates hepatic mitochondrial injury during rat renal ischemia-reperfusion injury

BACKGROUND

Renal ischemia-reperfusion injury (IRI) causes acute kidney injury as well as liver injury. Renal IRI depletes hepatic antioxidants, promotes hepatic inflammation and dysfunction through Tlr9 upregulation. There is no treatment available for liver injury during renal IRI. This study examines the hepatoprotective role of treprostinil, a prostacyclin analog, during renal IRI.

METHODS

Male Sprague-Dawley rats were divided into four groups: control, sham, IRI-placebo, or IRI-treprostinil and subjected to bilateral ischemia (45 min) followed by reperfusion (1-72 h). Placebo or treprostinil (100 ng/kg/min) was administered subcutaneously via an osmotic minipump.

RESULTS

Treprostinil significantly reduced peak serum creatinine, BUN, ALT and AST levels vs. IRI-placebo. Treprostinil also restored hepatic levels of superoxide dismutase, glutathione, catalase, and Gclc expression to baseline, while reducing lipid peroxidation vs. IRI-placebo. Additionally, treprostinil significantly reduced elevated hepatic Tlr9, Il-1β, Ccl2, Vcam1, and Serpine1 mRNA expression. Renal IRI increased hepatic apoptosis which was inhibited by treprostinil through reduced cytochrome c and cleaved caspase-3 protein expression. Treprostinil enhanced hepatic ATP concentrations and mitochondrial DNA copy number and improved mitochondrial dynamics by restoring Pgc-1α expression and significantly upregulating Mfn1, Mfn2, and Sirt3 levels, while reducing Drp-1 protein vs. IRI-placebo. Non-targeted semi-quantitative proteomics showed improved oxidative stress indices and ATP subunits in the IRI-treprostinil group.

CONCLUSIONS

Treprostinil improved hepatic function and antioxidant levels, while suppressing the inflammatory response and alleviating Tlr9-mediated apoptotic injury during renal IRI. Our study provides evidence of treprostinil's hepatoprotective effect, which supports the therapeutic potential of treprostinil in reducing hepatic injury during renal IRI.

Acute Kidney Injury and Organ Dysfunction: What Is the Role of Uremic Toxins?

Acute kidney injury (AKI), defined as an abrupt increase in serum creatinine, a reduced urinary output, or both, is experiencing considerable evolution in terms of our understanding of the pathophysiological mechanisms and its impact on other organs. Oxidative stress and reactive oxygen species (ROS) are main contributors to organ dysfunction in AKI, but they are not alone. The precise mechanisms behind multi-organ dysfunction are not yet fully accounted for. The building up of uremic toxins specific to AKI might be a plausible explanation for these disturbances. However, controversies have arisen around their effects in organs other than the kidney, because animal models usually depict AKI as a kidney-specific injury. Meanwhile, humans present AKI frequently in association with multi-organ failure (MOF). Until now, medium-molecular-weight molecules, such as inflammatory cytokines, have been proven to play a role in endothelial and epithelial injury, leading to increased permeability and capillary leakage, mainly in pulmonary and intestinal tissues.

Entacapone scavenges peroxynitrite and protects against kidney and liver injuries induced by renal ischemia/reperfusion in rats

BACKGROUND

Acute kidney injury (AKI), secondary to renal ischemia/reperfusion (I/R), is a serious problem associated with high mortality. The pathophysiology of AKI after renal I/R involves peroxynitrite production; hence, scavenging this metabolite may rescue AKI. Entacapone is a catechol-O-methyl transferase (COMT) inhibitor which elicits antioxidant activity by scavenging peroxynitrite. Therefore, we hypothesized that the peroxynitrite scavenging activity of entacopone protects against AKI after renal I/R injury in rats.

METHODS

Male Wistar rats were given either entacapone or a well-known peroxynitrite scavenger (FeTPPS) daily for 10 days before I/R procedures. I/R was induced by occluding both renal pedicles for 45 min followed by reperfusion for 24 h.

RESULTS

Pre-treatment with either entacapone or FeTPPS improved renal function as indicated by a significant reduction in serum creatinine and urea when compared to I/R group (P < 0.05). I/R injury increased renal levels of NO (4-folds, P < 0.05), iNOS (4-folds, P < 0.05), and 3-nitrotyrosine (5-folds, P < 0.05) compared to sham control. These effects were abrogated in animals pre-treated with entacapone or FeTPPS before being subjected to I/R (P < 0.05). In addition, entacapone or FeTPPS significantly inhibited I/R-induced elevation in renal TNF-α levels (78% and 58%, respectively) and caspase-3 activity (72% and 56%, respectively) indicating the reduction of both inflammation and apoptosis in the kidney (P < 0.05). The two drugs also improved kidney and liver functions in rats with renal I/R injury.

CONCLUSION

Our study showed that entacapone and FeTPPS protected against AKI and remote liver damage associated with renal I/R and this effect might be due to scavenging peroxynitrite and reducing nitrosative stress.

Renohepatic crosstalk: a review of the effects of acute kidney injury on the liver

Several theories regarding acute kidney injury (AKI)-related mortality have been entertained, although mounting evidence supports the paradigm that impaired kidney function directly and adversely affects the function of several remote organs. The kidneys and liver are fundamental to human metabolism and detoxification, and it is therefore hardly surprising that critical illness complicated by hepatorenal dysfunction portends a poor prognosis. Several diseases can simultaneously impact the proper functioning of the liver and kidneys, although this review will address the impact of AKI on liver function. While evidence for this relationship in humans remains sparse, we present supportive studies and then discuss the most likely mechanisms by which AKI can cause liver dysfunction. These include 'traditional' complications of AKI (uremia, volume overload and acute metabolic acidosis, among others) as well as systemic inflammation, hepatic leukocyte infiltration, cytokine-mediated liver injury and hepatic oxidative stress. We conclude by addressing the therapeutic implications of these findings to clinical medicine.

Acute Kidney Injury Sensitizes the Brain Vasculature to Ang II (Angiotensin II) Constriction via FGFBP1 (Fibroblast Growth Factor Binding Protein 1)

Acute kidney injury (AKI) causes multiple organ dysfunction. Here, we identify a possible mechanism that can drive brain vessel injury after AKI. We induced 30-minute bilateral renal ischemia-reperfusion injury in C57Bl/6 mice and isolated brain microvessels and macrovessels 24 hours or 1 week later to test their responses to vasoconstrictors and found that after AKI brain vessels were sensitized to Ang II (angiotensin II). Upregulation of FGF2 (fibroblast growth factor 2) and FGFBP1 (FGF binding protein 1) expression in both serum and kidney tissue after AKI suggested a potential contribution to the vascular sensitization. Administration of FGF2 and FGFBP1 proteins to isolated healthy brain vessels mimicked the sensitization to Ang II after AKI. Brain vessels in Fgfbp1-/- AKI mice failed to induce Ang II sensitization. Complementary to this, systemic treatment with the clinically used FGF receptor kinase inhibitor BGJ398 (Infigratinib) reversed the AKI-induced brain vascular sensitization to Ang II. All these findings lead to the conclusion that FGFBP1 is especially necessary for AKI-mediated brain vascular sensitization to Ang II and inhibitors of FGFR pathway may be beneficial in preventing AKI-induced brain vessel injury.

Systemic and sustained thioredoxin analogue prevents acute kidney injury and its-associated distant organ damage in renal ischemia reperfusion injury mice

The mortality of patients with acute kidney injury (AKI) remains high due to AKI associated-lung injury. An effective strategy for preventing both AKI and AKI-associated lung injury is urgently needed. Thioredoxin-1 (Trx) is a redox-active protein that possesses anti-oxidative, anti-apoptotic and anti-inflammatory properties including modulation of macrophage migration inhibitory factor (MIF), but its short half-life limits its clinical application. Therefore, we examined the preventive effect of a long-acting Trx, which is a fusion protein of albumin and Trx (HSA-Trx), against AKI and AKI-associated lung injury. Recombinant HSA-Trx was expressed using a Pichia expression system. AKI-induced lung injury mice were generated by bilateral renal ischemia reperfusion injury (IRI). HSA-Trx administration attenuated renal IRI and its-associated lung injury. Both renal and pulmonary oxidative stress were suppressed by HSA-Trx. Moreover, HSA-Trx inhibited elevations of plasma IL-6 and TNF-α level, and suppressed IL-6-CXCL1/2-mediated neutrophil infiltration into lung and TNF-α-mediated pulmonary apoptosis. Additionally, HSA-Trx suppressed renal IRI-induced MIF expression in kidney and lung. Administration of HSA-Trx resulted in a significant increase in the survival rate of renal IRI mice. Collectively, HSA-Trx could have therapeutic utility in preventing both AKI and AKI-associated lung injury as a consequence of its systemic and sustained multiple biological action.

Evaluation of the Biomarkers HMGB1 and IL-6 as Predictors of Mortality in Cirrhotic Patients with Acute Kidney Injury

Background

Acute kidney injury (AKI) affects from 20% to 50% of cirrhotic patients, and the one-month mortality rate is 60%. The main cause of AKI is bacterial infection, which worsens circulatory dysfunction through the release of HMGB1 and IL-6.

Objectives

To evaluate HMGB1 and IL-6 as biomarkers of morbidity/mortality.

Methods

Prospective, observational study of 25 hospitalised cirrhotic patients with AKI. Clinical and laboratory data were collected at the time of diagnosis of AKI, including serum HMGB1 and IL-6.

Results

The mean age was 55 years; 70% were male. Infections accounted for 13 cases. The 30-day and three-month mortality rates were 17.4% and 30.4%, respectively. HMGB1 levels were lower in survivors than in nonsurvivors at 30 days (1174.2 pg/mL versus 3338.5 pg/mL, p = 0.035), but not at three months (1540 pg/mL versus 2352 pg/mL, p = 0.243). Serum IL-6 levels were 43.3 pg/mL versus 153.3 pg/mL (p = 0.061) at 30 days and 35.8 pg/mL versus 87.9 pg/mL (p = 0.071) at three months, respectively. The area under the ROC curve for HMGB1 was 0.842 and 0.657, and that for IL-6 was 0.803 and 0.743 for discriminating nonsurvivors at 30 days and three months, respectively. In multivariate analysis, no biomarker was independently associated with mortality.

Conclusion

HMGB1 levels were associated with decreased survival in cirrhotics. Larger studies are needed to confirm our results.

Immunopathophysiology of trauma-related acute kidney injury

Physical trauma can affect any individual and is globally accountable for more than one in every ten deaths. Although direct severe kidney trauma is relatively infrequent, extrarenal tissue trauma frequently results in the development of acute kidney injury (AKI). Various causes, including haemorrhagic shock, rhabdomyolysis, use of nephrotoxic drugs and infectious complications, can trigger and exacerbate trauma-related AKI (TRAKI), particularly in the presence of pre-existing or trauma-specific risk factors. Injured, hypoxic and ischaemic tissues expose the organism to damage-associated and pathogen-associated molecular patterns, and oxidative stress, all of which initiate a complex immunopathophysiological response that results in macrocirculatory and microcirculatory disturbances in the kidney, and functional impairment. The simultaneous activation of components of innate immunity, including leukocytes, coagulation factors and complement proteins, drives kidney inflammation, glomerular and tubular damage, and breakdown of the blood-urine barrier. This immune response is also an integral part of the intense post-trauma crosstalk between the kidneys, the nervous system and other organs, which aggravates multi-organ dysfunction. Necessary lifesaving procedures used in trauma management might have ambivalent effects as they stabilize injured tissue and organs while simultaneously exacerbating kidney injury. Consequently, only a small number of pathophysiological and immunomodulatory therapeutic targets for TRAKI prevention have been proposed and evaluated.

The Yin and Yang of Alarmins in Regulation of Acute Kidney Injury

Acute kidney injury (AKI) is a major clinical burden affecting 20 to 50% of hospitalized and intensive care patients. Irrespective of the initiating factors, the immune system plays a major role in amplifying the disease pathogenesis with certain immune cells contributing to renal damage, whereas others offer protection and facilitate recovery. Alarmins are small molecules and proteins that include granulysins, high-mobility group box 1 protein, interleukin (IL)-1α, IL-16, IL-33, heat shock proteins, the Ca++ binding S100 proteins, adenosine triphosphate, and uric acid. Alarmins are mostly intracellular molecules, and their release to the extracellular milieu signals cellular stress or damage, generally leading to the recruitment of the cells of the immune system. Early studies indicated a pro-inflammatory role for the alarmins by contributing to immune-system dysregulation and worsening of AKI. However, recent developments demonstrate anti-inflammatory mechanisms of certain alarmins or alarmin-sensing receptors, which may participate in the prevention, resolution, and repair of AKI. This dual function of alarmins is intriguing and has confounded the role of alarmins in AKI. In this study, we review the contribution of various alarmins to the pathogenesis of AKI in experimental and clinical studies. We also analyze the approaches for the therapeutic utilization of alarmins for AKI.

Regular exercise and branched-chain amino acids prevent ischemic acute kidney injury-related muscle wasting in mice

Acute kidney injury (AKI) causes glucose and protein metabolism abnormalities that result in muscle wasting, thereby affecting the long-term prognosis of critical illness survivors. Here, we examined whether early intervention with treadmill exercise and branched-chain amino acids (BCAA) can prevent AKI-related muscle wasting and reduced physical performance in mice. Unilateral 15 min ischemia-reperfusion injury was induced in contralateral nephrectomized mice, and muscle histological and physiological changes were assessed and compared with those of pair-fed control mice, since AKI causes severe anorexia. Mice exercised for 30 min each day and received oral BCAA for 7 days after AKI insult. By day 7, ischemic AKI significantly decreased wet weight, myofiber cross-sectional area, and central mitochondrial volume density of the anterior tibialis muscle, and significantly reduced maximal exercise time. Regular exercise and BCAA prevented AKI-related muscle wasting and low physical performance by suppressing myostatin and atrogin-1 mRNA upregulation, and restoring reduced phosphorylated Akt and PGC-1α mRNA expression in the muscle. Ischemic AKI induces muscle wasting by accelerating muscle protein degradation and reducing protein synthesis; however, we found that regular exercise and BCAA prevented AKI-related muscle wasting without worsening kidney damage, suggesting that early rehabilitation with nutritional support could prevent AKI-related muscle wasting.

Chronic treatment with rofecoxib but not ischemic preconditioning of the myocardium ameliorates early intestinal damage following cardiac ischemia/reperfusion injury in rats

There is some recent evidence that cardiac ischemia/reperfusion (I/R) injury induces intestinal damage within days, which contributes to adverse cardiovascular outcomes after myocardial infarction. However, it is not clear whether remote gut injury has any detectable early signs, and whether different interventions aiming to reduce cardiac damage are also effective at protecting the intestine. Previously, we found that chronic treatment with rofecoxib, a selective inhibitor of cyclooxygenase-2 (COX-2), limited myocardial infarct size to a comparable extent as cardiac ischemic preconditioning (IPC) in rats subjected to 30-min coronary artery occlusion and 120-min reperfusion. In the present study, we aimed to analyse the early intestinal alterations caused by cardiac I/R injury, with or without the above-mentioned infart size-limiting interventions. We found that cardiac I/R injury induced histological changes in the small intestine within 2 h, which were accompanied by elevated tissue level of COX-2 and showed positive correlation with the activity of matrix metalloproteinase-2 (MMP-2), but not of MMP-9 in the plasma. All these changes were prevented by rofecoxib treatment. By contrast, cardiac IPC failed to reduce intestinal injury and plasma MMP-2 activity, although it prevented the transient reduction in jejunal blood flow in response to cardiac I/R. Our results demonstrate for the first time that rapid development of intestinal damage follows cardiac I/R, and that two similarly effective infarct size-limiting interventions, rofecoxib treatment and cardiac IPC, have different impacts on cardiac I/R-induced gut injury. Furthermore, intestinal damage correlates with plasma MMP-2 activity, which may be a biomarker for its early diagnosis.

Kidney Ischemia-Reperfusion Elicits Acute Liver Injury and Inflammatory Response

Ischemia-reperfusion (IR) is a common risk factor that causes acute kidney injury (AKI). AKI is associated with dysfunction of other organs also known as distant organ injury. The liver function is often compromised in patients with AKI and in animal models. However, the underlying mechanisms are not fully understood. Inflammatory response plays an important role in IR-induced tissue injury. Although increased proinflammatory cytokines have been detected in the kidney and the distant organs after renal IR, their original sources remain uncertain. In the present study, we investigated the acute effect of renal IR on hepatic inflammatory cytokine expression and the mechanism involved. Sprague-Dawley rats that were subjected to renal IR (ischemia for 45 min followed by reperfusion for 1 h or 6 h) had increased plasma levels of creatinine, urea, and transaminases, indicating kidney and liver injuries. There was a significant increase in the expression of proinflammatory cytokine mRNA (MCP-1, TNF-α, IL-6) in the kidney and liver in rats with renal IR. This was accompanied by a significant increase in proinflammatory cytokine protein levels in the plasma, kidney, and liver. Activation of a nuclear transcription factor kappa B (NF-κB) was detected in the liver after renal IR. The inflammatory foci and an increased myeloperoxidase (MPO) activity were detected in the liver after renal IR, indicating hepatic inflammatory response and leukocyte infiltration. These results suggest that renal IR can directly activate NF-κB and induce acute production of proinflammatory cytokines in the liver. Renal IR-induced hepatic inflammatory response may contribute to impaired liver function and systemic inflammation.

Intestinal microbiota control acute kidney injury severity by immune modulation

Intestinal microbiota impacts the host immune system and influences the outcomes of chronic diseases. However, it remains uncertain whether acute kidney injury (AKI) impacts intestinal microbiota or vice versa. To determine this, we investigated the mechanistic link between AKI, microbiota, and immune response in ischemia/reperfusion injury. Microbiota alteration and its biological consequences after ischemia/reperfusion injury were examined and the effect of dysbiotic microbiota on the outcome of AKI was also assessed by colonizing germ-free mice with post-AKI microbiota. The role of Th17, Th1, Tregs cells and macrophage polarization in mediating the renoprotective effect of antibiotic induced microbiota depletion in ischemia/reperfusion injury was also determined. Increase of Enterobacteriacea, decrease of Lactobacilli, and Ruminococacceae were found to be the hallmarks of ischemia/reperfusion injury induced dysbiosis and were associated with a decreased levels of short-chain fatty acids, intestinal inflammation and leaky gut. Colonizing germ-free mice with post-AKI microbiota worsened ischemia/reperfusion injury severity with exaggerated inflammation in recipient mice compared to colonizing with microbiota from sham operated mice. Microbiota depletion by oral antibiotics protected against ischemia/reperfusion injury. This renoprotective effect was associated with reduced Th 17, Th 1 response along with expansion of regulatory T cells, and M2 macrophages. Our study demonstrated a unique bidirectional relationship between the kidney and the intestine during AKI. Intestinal dysbiosis, inflammation and leaky gut are consequences of AKI but they also represent an important modifier determining post-AKI severity. Thus, targeting the intestinal microbiota might provide a novel therapeutic strategy in AKI.

Selective nanoparticle-mediated targeting of renal tubular Toll-like receptor 9 attenuates ischemic acute kidney injury

We developed an innovative therapy for ischemic acute kidney injury with discerning kidney-targeted delivery of a selective Toll-like receptor 9 (TLR9) antagonist in mice subjected to renal ischemia reperfusion injury. Our previous studies showed that mice deficient in renal proximal tubular TLR9 were protected against renal ischemia reperfusion injury demonstrating a critical role for renal proximal tubular TLR9 in generating ischemic acute kidney injury. Herein, we used 300-400 nm polymer-based mesoscale nanoparticles that localize to the renal tubules after intravenous injection. Mice were subjected to sham surgery or 30 minutes renal ischemia and reperfusion injury after receiving mesoscale nanoparticles encapsulated with a selective TLR9 antagonist (unmethylated CpG oligonucleotide ODN2088) or mesoscale nanoparticles encapsulating a negative control oligonucleotide. Mice treated with the encapsulated TLR9 antagonist either six hours before renal ischemia, at the time of reperfusion or 1.5 hours after reperfusion were protected against ischemic acute kidney injury. The ODN2088-encapsulated nanoparticles attenuated renal tubular necrosis, inflammation, decreased proinflammatory cytokine synthesis. neutrophil and macrophage infiltration and apoptosis, decreased DNA fragmentation and caspase 3/8 activation when compared to the negative control nanoparticle treated mice. Taken together, our studies further suggest that renal proximal tubular TLR9 activation exacerbates ischemic acute kidney injury by promoting renal tubular inflammation, apoptosis and necrosis after ischemia reperfusion. Thus, our studies suggest a potential promising therapy for ischemic acute kidney injury with selective kidney tubular targeting of TLR9 using mesoscale nanoparticle-based drug delivery.

Effects of low versus standard pressure pneumoperitoneum on renal syndecan-1 shedding and VEGF receptor-2 expression in living-donor nephrectomy: a randomized controlled study

Background

Laparoscopic nephrectomy is a preferred technique for living kidney donation. However, positive-pressure pneumoperitoneum may have an unfavorable effect on the remaining kidney and other distant organs due to inflamed vascular endothelium and renal tubular cell injury in response to increased systemic inflammation. Early detection of vascular endothelial and renal tubular response is needed to prevent further kidney injury due to increased intraabdominal pressure induced by pneumoperitoneum. Transperitoneal laparoscopic living donor nephrectomy represented a human model of mild increasing intraabdominal pressure. This study aimed to assess the effect of increased intraabdominal pressure on vascular endothelium and renal tubular cells by comparing the effects of low and standard pressure pneumoperitoneum on vascular endothelial growth factor receptor-2 (VEGFR-2) expression and the shedding of syndecan-1 as the early markers to a systemic inflammation.

Methods

We conducted a prospective randomized study on 44 patients undergoing laparoscopic donor nephrectomy. Subjects were assigned to standard (12 mmHg) or low pressure (8 mmHg) groups. Baseline, intraoperative, and postoperative plasma interleukin-6, syndecan-1, and sVEGFR-2 were quantified by ELISA. Syndecan-1 and VEGFR-2 expression were assessed immunohistochemically in renal cortex tissue. Renal tubule and peritubular capillary ultrastructures were examined using electron microscopy. Perioperative hemodynamic changes, end-tidal CO₂, serum creatinine, blood urea nitrogen, and urinary KIM-1 were recorded.

Results

The low pressure group showed lower intra- and postoperative heart rate, intraoperative plasma IL-6, sVEGFR-2 levels and plasma syndecan-1 than standard pressure group. Proximal tubule syndecan-1 expression was higher in the low pressure group. Proximal-distal tubules and peritubular capillary endothelium VEGFR-2 expression were lower in low pressure group. The low pressure group showed renal tubule and peritubular capillary ultrastructure with intact cell membranes, clear cell boundaries, and intact brush borders, while standard pressure group showed swollen nuclei, tenuous cell membrane, distant boundaries, vacuolizations, and detached brush borders.

Conclusion

The low pressure pneumoperitoneum attenuated the inflammatory response and resulted in reduction of syndecan-1 shedding and VEGFR-2 expression as the renal tubular and vascular endothelial proinflammatory markers to injury due to a systemic inflammation in laparoscopic nephrectomy.

Trial registration

ClinicalTrials.gov NCT:03219398, prospectively registered on July 17th, 2017.

Distant organ dysfunction in acute kidney injury

Acute kidney injury (AKI) is a common complication in critically ill patients and it is associated with increased morbidity and mortality. Epidemiological and clinical data show that AKI is linked to a wide range of distant organ injuries, with the lungs, heart, liver, and intestines representing the most clinically relevant affected organs. This distant organ injury during AKI predisposes patients to progression to multiple organ dysfunction syndrome and ultimately, death. The strongest direct evidence of distant organ injury occurring in AKI has been obtained from animal models. The identified mechanisms include systemic inflammatory changes, oxidative stress, increases in leucocyte trafficking and the activation of proapoptotic pathways. Understanding the pathways driving AKI-induced distal organ injury are critical for the development and refinement of therapies for the prevention and attenuation of AKI-related morbidity and mortality. The purpose of this review is to summarize both clinical and preclinical studies of AKI and its role in distant organ injury.

Recombinant thrombomodulin prevents acute lung injury induced by renal ischemia-reperfusion injury

Acute kidney injury (AKI) complicated by acute lung injury has a detrimental effect on mortality among critically ill patients. Recently, a renal ischemia-reperfusion (IR) model suggested the involvement of histones and neutrophil extracellular traps (NETs) in the development of distant lung injury after renal IR. Given that recombinant thrombomodulin (rTM) has anti-inflammatory roles by binding to circulating histones, we aimed to clarify its effect on distant lung injury induced by AKI in a murine bilateral renal IR model. Both pretreatment and delayed treatment with rTM significantly decreased pulmonary myeloperoxidase activity, but they did not affect renal dysfunction at 24 h after renal IR. Additionally, rTM mitigated the renal IR-augmented expression of proinflammatory cytokines (tumor necrosis factor-α, interleukin-6, and keratinocyte-derived chemokine), and vascular leakage, as well as the degree of lung damage. Intense histone accumulation and active NET formation occurred in both the kidneys and the lungs; however, rTM significantly decreased the histone and NET accumulation only in the lungs. Administration of rTM may have protective impact on the lungs after renal IR by blocking histone and NET accumulation in the lungs, although no protection was observed in the kidneys. Treatment with rTM may be an adjuvant strategy to attenuate distant lung injury complicating AKI.

Acute Kidney Injury and Pediatric Bone Health

Acute kidney injury (AKI) has been associated with deleterious impacts on a variety of body systems. While AKI is often accompanied by dysregulation of mineral metabolism-including alterations in calcium, phosphate, vitamin D, parathyroid hormone, fibroblast growth factor 23, and klotho-its direct effects on the skeletal system of children and adolescents remain largely unexplored. In this review, the pathophysiology of dysregulated mineral metabolism in AKI and its potential effects on skeletal health are discussed, including data associating AKI with fracture risk.

Fish oils protects against cecal ligation and puncture‑induced septic acute kidney injury via the regulation of inflammation, oxidative stress and apoptosis

Septic acute kidney injury (AKI) is usually caused by sepsis. ω3 fatty acid has been reported to suppress sepsis-induced organ dysfunction to a certain degree. The present study aimed to investigate the effects of ω3 fatty acid in septic renal injury. Sprague Dawley rats were used to establish a cecal ligation and puncture (CLP) model in order to mimic the development of septic injury. The rats were treated with dexamethasone and fish oils (FOs) for 4 days prior to CLP. Alterations in the morphology of the tissues, the renal function and the induction of inflammation, oxidative stress and apoptosis were evaluated. The effects of FOs on nuclear factor-κB (NF-κB), JAK2/STAT3 and p38-MAPK were determined. The rats of the CLP model group exhibited low survival rates and increased expression of serum creatine, blood urea nitrogen, neutrophil gelatinase-associated lipocalin, kidney injury molecule-1 and of proinflammatory cytokines. In addition, the levels of the markers of oxidative injury and apoptosis were increased. The induction of renal injury was notably reversed by administration of dexamethasone and FOs. The expression levels of the protein markers involved in inflammation and apoptosis were measured and the results indicated that FOs inhibited JAK/STAT3 and p-38MAPK signaling, while they concomitantly increased the expression of NF-κB. The present study highlighted that FOs improve CLP-induced mortality and renal injury by inhibiting inflammation, oxidative stress and apoptosis.

Mechanisms and treatment of organ failure in sepsis

Sepsis is a dysregulated immune response to an infection that leads to organ dysfunction. Knowledge of the pathophysiology of organ failure in sepsis is crucial for optimizing the management and treatment of patients and for the development of potential new therapies. In clinical practice, six major organ systems - the cardiovascular (including the microcirculation), respiratory, renal, neurological, haematological and hepatic systems - can be assessed and monitored, whereas others, such as the gut, are less accessible. Over the past 2 decades, considerable amounts of new data have helped improve our understanding of sepsis pathophysiology, including the regulation of inflammatory pathways and the role played by immune suppression during sepsis. The effects of impaired cellular function, including mitochondrial dysfunction and altered cell death mechanisms, on the development of organ dysfunction are also being unravelled. Insights have been gained into interactions between key organs (such as the kidneys and the gut) and organ-organ crosstalk during sepsis. The important role of the microcirculation in sepsis is increasingly apparent, and new techniques have been developed that make it possible to visualize the microcirculation at the bedside, although these techniques are only research tools at present.

Piperine pretreatment attenuates renal ischemia-reperfusion induced liver injury

Background

Remote organ injury is one of the complications which are developed following ischemia-reperfusion induced acute kidney injury (AKI), dramatically increasing its mortality rate. The aim of the present study was to investigate the effect of piperine pretreatment on liver dysfunction following ischemia-reperfusion induced AKI.

Materials and methods

Acute kidney injury was induced by 30 min-bilateral renal ischemia followed by 24 h of reperfusion. To investigate liver damages, the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) enzymes were measured in plasma. In order to study oxidative stress, malondialdehyde (MDA) and ferric reducing antioxidant power (FRAP) levels were measured. Furthermore, the expression of intercellular adhesion molecule-1 (ICAM-1) mRNA along with infiltration of leukocytes in the liver tissue was measured for inflammation assessment. Histopathological damages were studied through measuring the extent of cellular fibrosis, sinusoidal dilatation, and vascular congestion in liver tissue.

Results

Following acute kidney injury, AST, ALT, and ALP levels in plasma, MDA level and ICAM-1 expression in the liver tissue, infiltration of leukocytes into the interstitium, and hepatic histopathologic damages increased significantly, while FRAP decreased. Pretreatment with piperine at 10 and 20 mg/kg body weight was able to improve these damages, such that some of them reached its value in the sham group, though piperine in the 20 mg/kg was more effective.

Conclusions

The results of this study suggest that ischemia-reperfusion induced AKI result in hepatic damages, and pretreatment with piperine can prevent development of these damages through its antioxidant and anti-inflammatory properties.

Paneth cell ablation increases the small intestinal injury during acute necrotizing pancreatitis in rats

The present work aimed to investigate the role of Paneth cells in small intestinal injury during acute necrotizing pancreatitis (ANP) using rat models established by injection of dithizone, a metal chelator of zinc with the ability to selectively ablate Paneth cells. Sprague‑Dawley rats were randomly divided into four groups: Sham‑operated group, ANP group (3.5% sodium taurocholate solution, 1 ml/kg body weight), dithizone group (100 mg/kg of body weight) and ANP + dithizone group (sodium taurocholate solution was administered 6 h after dithizone injection). Each group was further divided into five subgroups (6, 12, 24, 36 and 48 h) based on the time period between induction of the model and sample collection. The present results suggested the number of Paneth cells was gradually decreased in the ANP group in a time‑dependent manner. Most of the Paneth cells were ablated in the ANP + dithizone group at 6 h, but a subset of Paneth cells recovered after 24‑48 h. Compared with the ANP group, combination of dithizone and ANP significantly induced more severe histopathological injuries in the pancreas and distal ileum, with higher Schmidt and Chiu's scores, respectively. Additionally, increased expression levels of tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β and IL‑17A were detected in the ileum, causing an increase in intestinal permeability, as assessed by a decrease in the expression level of the intestinal tight junction protein occludin and high plasma levels of diamine oxidase and D‑lactate. The increase in intestinal permeability led to the translocation of bacteria to the bloodstream, triggering systemic inflammation, as assessed by the increased plasma levels of TNF‑α, IL‑1β and IL‑17A, reducing the survival rates of rats, which was 66.7% and 83.3% in the ANP + dithizone and the ANP group, respectively. The increase in intestinal endoplasmic reticulum stress, as assessed by high expression levels of binding‑immunoglobulin protein and activating transcription factor 6, may be one mechanism associated with Paneth cells loss and intestinal barrier impairment during ANP. Collectively, the present study suggested that the absence of Paneth cells may be an important factor involved in intestinal injury, promoting the progression of ANP.

Impact of renal ischemia/reperfusion injury on the rat Kupffer cell as a remote cell: A biochemical, histological, immunohistochemical, and electron microscopic study

Almost all transplanted solid organs are exposed to some degree of ischemia-reperfusion (IR) damage. It is interesting to know that this IR damage affects various remote tissues including the liver and resulted in serious adverse effects. Liver injury triggers different responses of liver tissue especially Kupffer cells (KCs). The goal of this current study is to assess the biochemical and morphological changes of hepatic KCs after the induction of renal ischemia-reperfusion (RIR) and point out their role in remote liver injury after RIR. Sixteen male Sprague-Dawley rats were randomly divided into two equal groups: Group I; sham group. Group II; renal ischemia reperfusion (IR) group in which rats were exposed to renal ischemia for 45 min followed by renal reperfusion for 48 h. Three rats from each group were subjected to charcoal injection to evaluate KCs activity. Specimens of rat liver from each group were obtained and processed for biochemical, light microscopic and ultramicroscopic examination. The current results showed elevated serum levels of AST and ALT. The liver HGF-α protein expression increased in IR group compared to the sham group. In IR group, numerous charcoal labeled KCs were observed mainly localized around the central vein. Scanning electron micrographs showed complex primary and secondary foot process of the KCs. Ultrastructural study showed KCs with multiple cytoplasmic vacuoles, lysosomes and mitochondria, rough endoplasmic reticulum and ribosomes. Immuno-histochemical study showed more tumor necrosis factor-α (TNF-α) expression in KCs than the sham group. These results collectively demonstrated that renal IR produced biochemical and morphological changes in the liver KCs and theses cells might have a role in the remote liver injury after renal IR. This might be one of the mechanisms through which RIR affects the liver.

Tetramethylpyrazine Prevents Contrast-Induced Nephropathy via Modulating Tubular Cell Mitophagy and Suppressing Mitochondrial Fragmentation, CCL2/CCR2-Mediated Inflammation, and Intestinal Injury

Contrast-induced nephropathy (CIN) is a leading cause of hospital-acquired acute kidney injury (AKI), but detailed pathogenesis and effectual remedy remain elusive. Here, we tested the hypothesis that contrast media (CM) impaired mitochondrial quality control (MQC) in tubules, including mitochondrial fragmentation and mitophagy, induced systemic inflammation, and intestinal injury. Since we previously demonstrated that the natural antioxidant 2,3,5,6-tetramethylpyrazine (TMP) can be a protectant against CIN, we moreover investigated the involved renoprotective mechanisms of TMP. In a well-established CIN rat model, renal functions, urinary AKI biomarkers, and renal reactive oxygen species (ROS) production were measured. Mitochondrial damage and mitophagy were detected by transmission electron microscopy (TEM) and western blot. The abundance of Drp1 and Mfn2 by western blot and immunohistochemistry (IHC) was used to evaluate mitochondrial fragmentation. TUNEL staining, TEM, and the abundance of cleaved-caspase 3 and procaspase 9 were used to assay apoptosis. We demonstrated that increased mitophagy, mitochondrial fragmentation, ROS generation, autophagy, and apoptosis occurred in renal tubular cells. These phenomena were accompanied by renal dysfunction and an increased excretion of urinary AKI biomarkers. Meanwhile, CM exposure resulted in concurrent small intestinal injury and villous capillary endothelial apoptosis. The abundance of the inflammatory cytokines CCL2 and CCR2 markedly increased in the renal tubules of CIN rats, accompanied by increased concentrations of IL-6 and TNF-α in the kidneys and the serum. Interestingly, TMP efficiently prevented CM-induced kidney injury in vivo by reversing these pathological processes. Mechanistically, TMP inhibited the CM-induced activation of the CCL2/CCR2 pathway, ameliorated renal oxidative stress and aberrant mitochondrial dynamics, and modulated mitophagy in tubular cells. In summary, this study demonstrated novel pathological mechanisms of CIN, that is, impairing MQC, inducing CCL2/CCR2-mediated inflammation and small intestinal injury, and provided novel renoprotective mechanisms of TMP; thus, TMP may be a promising therapeutic agent for CIN.

Renal ischemia/reperfusion induced learning and memory deficit in the rat: Insights into underlying molecular and cellular mechanisms

Distance organ dysfunction is the major cause of death in the patients with acute kidney injury (AKI). However, the neurobiological basis of AKI-induced brain disorders and their mediators are poorly understood. This study was aimed to find out the links between AKI and brain injury and also the underlying cellular and electrophysiological mechanisms of memory deficit following induction of AKI via different experimental models of renal ischemia with or without uremia and uremia without renal ischemia. Fifty four male Sprague-Dawley rats were divided into 4 groups that underwent 1-h bilateral or 2-h unilateral renal ischemia followed by 1-day reperfusion (BIR and UIR, respectively), and 1-day following bilateral nephrectomy (BNX) or sham-operation. There were 2 subgroups in each group, which blood-brain barrier (BBB) integrity was evaluated in one subgroup. The other subgroup was used for recordings electrophysiological activities of the hippocampus; and after blood sampling and sacrificing animal, the cerebral hemispheres were removed and preserved for performing stereological study and Western-blotting of caspase-3 in the left and right hippocampus, respectively. Plasma urea and creatinine and CA1 neuronal loss were largely increased by BNX and BIR, but slightly by UIR. Apoptosis was stimulated in the hippocampus intensively by BIR but moderately by UIR and BNX. However, BIR and UIR were associated with profoundly disturbed BBB, increased CA1 neuronal excitability, impaired LTP induction and memory deficit. Therefore, AKI most likely through inflammatory mediators leads to hippocampal apoptosis and electrophysiological impairments, BBB disruption and memory loss, whereas uremia may contribute to necrotic neuronal death.