The pathogenesis of renal injury in obstructive jaundice: A review of underlying mechanisms, inducible agents and therapeutic strategies

Exploration of the pathogenesis of nephrotic syndrome and traditional Chinese medicine intervention based on gut microbiota

Nephrotic syndrome (NS) represents a prevalent syndrome among various chronic kidney disease pathologies and is known for its higher severity and worse prognosis compared with chronic glomerulonephritis. Understanding its pathogenesis and identifying more effective treatment modalities have long been a concern of kidney specialists. With the introduction of the gut-kidney axis concept and the progress in omics technologies, alterations in the gut microbiota have been observed in primary and secondary NS. This link has been extensively researched in conditions such as diabetic nephropathy and immunoglobulin A (IgA) nephropathy. Thus, dysbiosis of the gut microbiota is seen as a crucial contributing factor in NS; however, there is a lack of comprehensive reviews that elucidate the changes in the gut microbiota across different NS conditions and that describe its mechanistic role in the disease. Moreover, serving as an innate regulator of the gut microbiota, traditional Chinese medicine (TCM) has the potential to exert a profound impact on the expression of inflammation-promoting agents, decreasing the levels of endotoxins and uremic toxins. In addition, it strengthens the stability of the intestinal barrier while controlling the metabolic function of the body through its efficient modulation of the gut microbiota. This intricate process yields far-reaching consequences for NS.

FXR contributes to obstructive jaundice-induced vascular hyporeactivity in mesenteric arteries by reconstituting BKCa channels

OBJECTIVE

Vascular hyporeactivity increases with the incidence of obstructive jaundice (OJ). Evidence suggests that OJ activates the farnesoid X receptor (FXR) as well as the large-conductance Ca2+-activated K+ (BKCa or MaxiK) channel. This study was designed to explore the role of the FXR in vascular hyporesponsiveness induced by cholestasis.

METHODS

The OJ model rats were constructed by bile duct ligation (BDL) and treated with an FXR agonist or antagonist. Vasoconstriction of the mesenteric arteries (MAs) was assessed in vitro. Whole-cell patch clamp recordings were used to investigate BKCa channel function. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot were used to detect mRNA and protein levels.

RESULTS

A significant increase in vascular tone and responsiveness to norepinephrine (NE) was observed after the MaxiK channel blocker (IbTX) was administered. This effect was pronounced in BDL animals and can be mimicked by the FXR agonist GW4064 and inhibited by the FXR antagonist Z-guggulsterone (Z-Gu). GW4064 has a similar effect as cholestasis in promoting MaxiK currents in isolated arterial smooth muscle cells (ASMCs), while Z-Gu blunted this effect. The mRNA and protein expression of FXR and MaxiK-β1, but not MaxiK-α, were significantly increased in the BDL group in comparison to the sham. Furthermore, activation or inhibition of FXR promoted or inhibited the mRNA and protein expression of the MaxiK-β1 subunit, respectively.

CONCLUSION

Activation of FXR enhances the capability of the MaxiK channel to regulate vascular tone and leads to vascular hyporesponsiveness in the MAs of BDL rats, which may be mediated by the nonparallel upregulation of MaxiK-α and MaxiK-β1 subunit expression.

Cyclosporine A-induced systemic metabolic perturbations in rats: A comprehensive metabolome analysis

A better understanding of cyclosporine A (CsA)-induced nephro- and hepatotoxicity at the molecular level is necessary for safe and effective use. Utilizing a sophisticated study design, this study explored metabolic alterations after long-term CsA treatment in vivo. Rats were exposed to CsA with 4, 10, and 25 mg/kg for 4 weeks and then sacrificed to obtain liver, kidney, urine, and serum for untargeted metabolomics analysis. Differential network analysis was conducted to explore the biological relevance of metabolites significantly altered by toxicity-induced disturbance. Dose-dependent toxicity was observed in all biospecimens. The toxic effects were characterized by alterations of metabolites related to energy metabolism and cellular membrane composition, which could lead to the cholestasis-induced accumulation of bile acids in the tissues. The unfavorable impacts were also demonstrated in the serum and urine. Intriguingly, phenylacetylglycine was increased in the kidney, urine, and serum treated with high doses versus controls. Differential correlation network analysis revealed the strong correlations of deoxycytidine and guanosine with other metabolites in the network, which highlighted the influence of repeated CsA exposure on DNA synthesis. Overall, prolonged CsA administration had system-level dose-dependent effects on the metabolome in treated rats, suggesting the need for careful usage and dose adjustment.

Hyocholic acid retards renal fibrosis by regulating lipid metabolism and inflammatory response in a sheep model

The kidneys are vital organs that regulate metabolic homeostasis in the body, filter waste products from the blood, and remove extrahepatic bile acids. We previously found that the dietary supplementation of hyocholic acid alleviated the sheep body lipid deposition and decreased kidney weight. This study evaluated hyocholic acid's (HCA) roles and mechanisms on lipid metabolism and anti-inflammatory function in the kidney under a high-energy diet. Histomicrograph showing the apparent improvement by HCA by attenuating structural damage. The HCA treatment reduced the renal accumulation of cholesterol. Bile acid receptors such as LXR and FXR were activated at the protein level. HCA significantly altered several genes related to immune response (NF-κB, IL-6, and MCP1) and fibrosis (TGF-β, Col1α1, and α-SMA). These significant changes correlated with renal lipid accumulation. The KEGG pathways including non-alcoholic fatty liver disease, insulin resistance, TNF signaling pathway, and Th17 cell differentiation were enriched and NF-κB, IL-6, and TGF-β were identified as the core interconnected genes. This study revealed that HCA plays an efficient role in alleviating kidney lipids accumulation and inflammatory response through crucial genes such as FXR, LXR, HMGCR, NF-κB, IL-6, MCP1, and TGF-β, and expand our understanding of HCA's role in kidney function. In conclusion, HCA mitigated kidney fibrosis, lipid metabolism disorders and immune responses induced by a high-energy diet by regulating a potential LXR/SREBP2/TGF-β-NF-κB signaling pathway.

Pathophysiology of Hepatorenal Syndrome - Acute Kidney Injury

Hepatorenal syndrome is a complication of liver cirrhosis with ascites that results from the complex interplay of many pathogenetic mechanisms. Advanced cirrhosis is characterized by the development of hemodynamic changes of splanchnic and systemic arterial vasodilatation, with paradoxical renal vasoconstriction and renal hypoperfusion. Cirrhosis is also an inflammatory state. The inflammatory cascade is initiated by a portal hypertension-induced increased translocation of bacteria, bacterial products, and endotoxins from the gut to the splanchnic and then to the systemic circulation. The inflammation, whether sterile or related to infection, is responsible for renal microcirculatory dysfunction, microthrombi formation, renal tubular oxidative stress, and tubular damage. Of course, many of the bacterial products also have vasodilatory properties, potentially exaggerating the state of vasodilatation and worsening the hemodynamic instability in these patients. The presence of cardiac dysfunction, related to cirrhotic cardiomyopathy, with its associated systolic incompetence, can aggravate the mismatch between the circulatory capacitance and the circulation volume, worsening the extent of the effective arterial underfilling, with lower renal perfusion pressure, contributing to renal hypoperfusion and increasing the risk for development of acute kidney injury. The presence of tense ascites can exert an intra-abdominal compartmental syndrome effect on the renal circulation, causing renal congestion and hampering glomerular filtration. Other contributing factors to renal dysfunction include the tubular damaging effects of cholestasis and adrenal dysfunction. Future developments include the use of metabolomics to identify metabolic pathways that can lead to the development of renal dysfunction, with the potential of identifying biomarkers for early diagnosis of renal dysfunction and the development of treatment strategies.

A novel ameliorated rat model of reversible obstructive jaundice

Obstructive jaundice is a common clinical symptom generally caused by bile duct stones, inflammatory hyperplasia, and tumors. It is characterized by hyperbilirubinemia and may trigger a variety of complications such as hypotension, kidney injury, endotoxemia, multiple organ dysfunction syndrome, and even death (Pavlidis and Pavlidis, 2018; Liu et al., 2021). Relieving bile duct obstruction and providing adequate drainage have been considered as the most effective therapies for obstructive jaundice. However, it has not yet been established whether it is beneficial to treat affected patients by pre-operative biliary drainage (Blacker et al., 2021). Moreover, the pathophysiological changes or mechanisms associated with the reversal of organ function following the relief of bile-duct obstruction are unclear (Huang et al., 2004). Therefore, it is necessary to establish an experimental model of reversible obstructive jaundice to simulate biliary drainage in clinical practice.

Toll-like receptor 4 signaling pathway mediates both liver and kidney injuries in mice with hepatorenal syndrome

Hepatorenal syndrome (HRS) is a complication of cirrhosis with high morbidity and mortality. Nevertheless, the underlying mechanism involving how kidney injury aggravates the progression of cirrhosis remains unclear. This study aims to explore the role of the Toll-like receptor 4 (TLR4) signaling pathway in mediating liver and kidney injuries in HRS mice induced by unilateral ureteral obstruction (UUO) and/or bile duct ligation (BDL). Two weeks after UUO, there were no obvious pathological changes in mouse liver and the unligated side of kidney. Nevertheless, impaired liver and kidney functions, inflammatory response, and fibrosis were examined in mice after 2 wk of BDL. Compared with those of other groups, mice in the BDL + UUO group presented severer liver and kidney injuries, higher levels of inflammatory factors, and faster deposition of collagens, suggesting that kidney injuries accelerated the aggravation of HRS. Correlation analysis identified a positive correlation between expression levels of inflammatory factors and fibrotic levels. Meanwhile, TLR4 and its ligand MyD88 were upregulated during the process of liver and kidney injuries in HRS mice. Further animal experiments in transgenic TLR4^-/- mice or in those treated with TAK242, a small molecule inhibitor of TLR4, showed that blocking the TLR4 signaling pathway significantly improved survival quality and survival rate in HRS mice by alleviating liver fibrosis and kidney injury. It is concluded that kidney dysfunction plays an important role in the aggravation of cirrhosis, which may be attributed to the TLR4 signaling pathway. Targeting TLR4 could be a promising therapeutic strategy for protecting both liver and kidneys in patients with HRS.NEW & NOTEWORTHY Our study established BDL, UUO, and BDL + UUO models, providing a novel idea for analyzing liver and kidney diseases. It is highlighted that the kidney injury accelerated the aggravation of HRS via inflammatory response, which could be protected by inhibiting the TLR4 signaling pathway. We believed that targeting TLR4 was a promising therapeutic strategy for protecting both liver and kidney functions in patients with HRS.

The Protective Effect of Sulodexide on Acute Lung Injury Induced by a Murine Model of Obstructive Jaundice

Introduction

The effect of sulodexide (SLX) on obstructive jaundice- (OJ-) induced acute lung injury (ALI) in rats was examined in this study.

Methods

In this study, 48 rats were randomly assigned to one of six groups: sham, OJ, OJ+saline, OJ+SLX (0.5 mg/ml/d), OJ+SLX (1 mg/ml/d), and OJ+SLX (2 mg/ml/d). The pathological lung injury was assessed by histological analysis and lung injury grading. ELISA kits were used to evaluate the expression of IL-6, IL-1, TNF-α, and syndecan-1 (SDC-1) in bronchoalveolar lavage fluids (BALFs). Commercial assay kits were performed to evaluate malondialdehyde (MDA) production and catalase (CAT) activity in lung tissues. The apoptosis was assessed by TUNEL assay. The lung microvascular permeability was investigated using Evans blue leakage, lung wet/dry weight (W/D) ratio, and lung permeability index (LPI). SDC-1, claudin-5, ZO-1, and VE cadherin expression levels in lung tissues were measured using Western blot.

Results

The OJ-induced ALI rats showed severe lung injury. The value of IL-6, IL-1β, TNF-α, and SDC-1 in BALFs was remarkedly increased in the OJ group. MDA content, apoptotic area, apoptotic molecules, and SDC-1 level were all higher in the OJ group's lung tissues than in the sham group. CAT activity, Evans blue leakage, W/D ratio, LPI, and expression of claudin-5, ZO-1, and VE cadherin were all lower in the OJ group compared to the sham group. The degenerative alterations in lung tissue improved after 7 days of treatment with 2 mg/ml SLX. The BALFs had lower amounts of IL-6, IL-1, TNF-α, and SDC-1. The SLX therapy reduced MDA levels while restoring CAT activity. In lung tissues, SLX reduced apoptotic area and SDC-1 expression. SLX reduced lung microvascular permeability by raising the expression of Claudin-5, ZO-1, and VE-cadherin in lung tissue when compared to the OJ group.

Conclusion

The results suggested that SLX attenuates OJ-induced ALI in rats by protecting the pulmonary microvascular endothelial barrier.

Biliary Drainage Reduces Intestinal Barrier Damage in Obstructive Jaundice by Regulating Autophagy

This study aims to investigate the mechanism by which biliary drainage reduces intestinal barrier damage in obstructive jaundice (OJ). A biliary drainage model was established in rats with OJ to detect changes in inflammatory factors and diamine oxidase (DAO), a marker of intestinal mucosal damage. The expression of autophagy-related genes in the intestinal mucosa after biliary drainage was detected using a reverse transcription-polymerase chain reaction. The rats were separated into two groups that received the autophagy activator rapamycin (RAPA) or the autophagy inhibitor 3-methyladenine (3-MA) to further investigate whether biliary drainage could alleviate the inflammatory response, oxidative stress, mitochondrial complex IV damage, and thus barrier damage in rats with OJ. The expression levels of inflammatory factors and the serum DAO content were increased in rats with OJ (P < 0.05). Biliary drainage further induced autophagy, reduced the expression levels of inflammatory factors, decreased the serum DAO content (P < 0.05), and improved intestinal mucosal damage. Administration of RAPA to OJ rats with biliary drainage increased autophagy (P < 0.05); decreased inflammatory factor secretion (P < 0.05), the serum DAO content (P < 0.05), oxidative stress (P < 0.05), and mitochondrial respiratory chain complex IV damage (P < 0.05); and ameliorated intestinal mucosal injury in OJ rats. When OJ rats were treated with 3-MA, intestinal mucosal injury, intestinal mitochondrial injury, and oxidative stress were all aggravated (P < 0.05). Biliary drainage can reduce the expression of inflammatory factors, oxidative stress, and mitochondrial injury by inducing intestinal mucosal autophagy in OJ rats, thus suggesting its role in the alleviation of intestinal mucosal injury.

Comparative Study of the Results of Operations in Patients with Tumor and Non-Tumor Obstructive Jaundice Who Received and Did Not Receive Antioxidant Therapy for the Correction of Endotoxemia, Glycolysis, and Oxidative Stress

Purpose: To compare the results of surgical treatment and changes in biomarkers of cholestasis, endotoxicosis, cytolysis, lipid peroxidation, glycolysis disorders, and inflammation in patients with benign and malignant obstructive jaundice (OJ) in patients receiving and not receiving antioxidant pharmacotherapy (AOT). Patients and methods: The study included 113 patients (aged 21–90 years; 47 males and 66 females) who received surgical intervention for OJ due to non-malignant (71%) or malignant tumor (29%) etiologies. Patients were divided into two groups: Group I (n = 61) who did not receive AOT and Group II (n = 51) who received AOT (succinate-containing drug Reamberin) as part of detoxification infusion therapy. The surgical approach and scope of interventions in both groups were identical. Dynamic indicators of endotoxicosis, cholestasis, and cytolysis (total, direct, and indirect bilirubin, alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase [AP] and gamma-glutamyltransferase [GGT]), kidney function (urea), lipid peroxidation (malonic dialdehyde, MDA), inflammation (leukocytosis), and glycolysis disorders (lactate dehydrogenase (LDH), glucose) were evaluated. Results: Tumor jaundice, unlike non-tumor jaundice, persisted and was characterized by a more severe course, a higher level of hyperbilirubinemia, and lipid peroxidation. The prognostic value of the direct (and total) bilirubin, MDA, glycemia, and leukocytosis levels on the day of hospitalization, which increased significantly in severe jaundice and, especially, in deceased patients, was established. Decompression interventions significantly reduced levels of markers of liver failure, cytolysis, cholestasis, and lipid peroxidation on day 3 after decompression by 1.5–3 times from initial levels; this is better achieved in non-tumor OJ. However, 8 days after decompression, most patients did not normalize the parameters studied in both groups. AOT favorably influenced the dynamics (on day 8 after decompression) of total and direct bilirubin, ALT, AST, MDA, and leukocytosis in non-tumor jaundice, as well as the dynamics of direct bilirubin, AST, MDA, glucose, and LDH in tumor jaundice. Clinically, in the AOT group, a two-fold reduction in the operative and non-operative complications was recorded (from 23% to 11.5%), a reduction in the duration of biliary drainage by 30%, the length of stay in intensive care units was reduced by 5 days, and even hospital mortality decreased, especially in malignancy-induced OJ. Conclusion: A mechanism for the development of liver failure in OJ is oxidative stress with the appearance of enhanced lipid peroxidation and accompanied by hepatocyte necrosis. Inclusion of AOT in perioperative treatment in these patients improves treatment outcomes.

Hepatorenal Syndrome: Pathophysiology

Hepatorenal syndrome (HRS) is defined as a functional renal failure without major histologic changes in individuals with severe liver disease and it is associated with a high mortality rate. Renal hypoperfusion due to marked vasoconstriction as a result of complex circulatory dysfunction has been suggested to be the cornerstone of HRS. Splanchnic and peripheral arterial vasodilation and cirrhotic cardiomyopathy result in effective arterial hypovolemia and compensatory activation of vasoconstrictor mechanisms. The efficacy of current therapeutic strategies targeting this circulatory dysfunction is limited. Increasing evidence suggests a substantial role of systemic inflammation in HRS via either vascular or direct renal effects. Here we summarize the current understanding of HRS pathophysiology.

Physical Exercise Repairs Obstructive Jaundice-Induced Damage to Intestinal Mucosal Barrier Function via H2S-Mediated Regulation of the HMGB1/Toll Like Receptors 4/Nuclear Factor Kappa B Pathway

The present study aimed to determine the effect of aerobic exercise on improving damage to intestinal mucosal barrier function caused by obstructive jaundice (OJ) and explore the mechanism. Fifty male KM mice were divided into five groups: sham operation group (S), model group (M), exercise group (TM), DL-propargylglycine + exercise (PT) group, and sodium hydrosulfide + exercise (NT) group. Additionally, mice in S group underwent common bile duct ligation for 48 h to establish a murine obstructive jaundice model. In PT group, propargylglycine (40 mg/kg) was intraperitoneally injected 7 days after surgery. NaHS (50 μmol/kg) was intraperitoneally injected into mice in the NT group 7 days after surgery. The TM group, NT group and PT group exercised on a slope of 0% at a speed of 10 m/min without weight training (30 min/day). HE staining showed that the intestinal mucosa of group M was atrophied and that the villi were broken. The intestinal mucosal structure of mice in the TM group was improved. Serum assays showed that H2S levels were higher in the TM group than in the M group; compared with the levels in the TM group, the PT group levels were decreased and the NT group levels were increased. In addition, aerobic exercise inhibits the HMGB1/TLR4/NF-κB signaling pathway by promoting endogenous H2S production, thereby exerting a protective effect on the intestinal mucosal barrier.