Role of dihydroceramides in the progression of acute-on-chronic liver failure in rats

The Immunoregulatory and Regenerative Potential of Activated Human Stem Cell Secretome Mitigates Acute-on-Chronic Liver Failure in a Rat Model

Acute-on-chronic liver failure (ACLF) is a syndrome marked by sudden liver function decline and multiorgan failure, predominantly acute kidney injury (AKY), in patients with chronic liver disease. Unregulated inflammation is a hallmark of ACLF; however, the key drivers of ACLF are not fully understood. This study explores the therapeutic properties of human mesenchymal stem cell (MSC) secretome, particularly focusing on its enhanced anti-inflammatory and pro-regenerative properties after the in vitro preconditioning of the cells. We evaluated the efficacy of the systemic administration of MSC secretome in preventing liver failure and AKI in a rat ACLF model where chronic liver disease was induced using by the administration of porcine serum, followed by D-galN/LPS administration to induce acute failure. After ACLF induction, animals were treated with saline (ACLF group) or MSC-derived secretome (ACLF-secretome group). The study revealed that MSC-secretome administration strongly reduced liver histological damage in the ACLF group, which was correlated with higher hepatocyte proliferation, increased hepatic and systemic anti-inflammatory molecule levels, and reduced neutrophil and macrophage infiltration. Additionally, renal examination revealed that MSC-secretome treatment mitigated tubular injuries, reduced apoptosis, and downregulated injury markers. These improvements were linked to increased survival rates in the ACLF-secretome group, endorsing MSC secretomes as a promising therapy for multiorgan failure in ACLF.

Asiatic acid ameliorates rifampicin- and isoniazid-induced liver injury in vivo by regulating sphingolipid metabolism and mitogen-activated protein kinase signalling pathways

In this study, we aimed to determine whether asiatic acid (AA) exerts any therapeutic effects on rifampicin (RFP)- and isoniazid (INH)-induced liver injury and elucidate the underlying mechanisms. Briefly, liver injury in mice was induced via RFP and INH administration. We investigated the effects and potential action mechanisms of AA on liver injury using transcriptomics, metabolomics and various examinations. We found that AA significantly ameliorated the pathological changes in liver tissues and decreased the transaminase activity, inflammation and oxidative stress damage. Transcriptomics revealed 147 differentially expressed genes (DEGs) between the AA and model groups that were enriched in metabolic and mitogen-activated protein kinase (MAPK) signalling pathways. Metabolomics revealed 778 differentially expressed metabolites between the AA and model groups. Furthermore, integrated transcriptomics and metabolomics analyses revealed strong correlations between DEGs and differentially expressed metabolites and indicated that AA regulates the sphingolipid metabolism by inhibiting the expression of delta 4-desaturase, sphingolipid 1. Experimental results confirmed that AA inhibited the MAPK signalling pathway. In summary, AA inhibits inflammation and oxidative stress damage by regulating the sphingolipid metabolism pathway and blocking the MAPK signalling pathway, thereby relieving the RFP/INH-induced liver injury.

The progress to establish optimal animal models for the study of acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) defines a complicated and multifaceted syndrome characterized by acute liver dysfunction following an acute insult on the basis of chronic liver diseases. It is usually concurrent with bacterial infection and multi-organ failure resulting in high short-term mortality. Based on the cohort studies in ACLF worldwide, the clinical course of ACLF was demonstrated to comprise three major stages including chronic liver injury, acute hepatic/extrahepatic insult, and systemic inflammatory response caused by over-reactive immune system especially bacterial infection. However, due to the lack of optimal experimental animal models for ACLF, the progress of basic study on ACLF is limping. Though several experimental ACLF models were established, none of them can recapitulate and simulate the whole pathological process of ACLF patients. Recently, we have developed a novel mouse model for ACLF combining chronic liver injury [injection of carbon tetrachloride (CCl₄) for 8 weeks], acute hepatic insult (injection of a double dose CCl₄), and bacterial infection (intraperitoneal injection of Klebsiella pneumoniae), which could recapitulate the major clinical features of patients with ACLF worsened by bacterial infection.

Hematological and biochemical investigations on the effect of curcumin and Thymoquinone in male mice exposed to Thioacetamide

Currently, living organisms are increasingly exposed to many toxic chemicals in the environment. These substances pose a threat to human life, other living organisms and ecosystem. In fact, there is an increasing requirement to search for safe therapeutic sources today. Medicinal plants and natural products have become of great importance globally because of their therapeutic potential and medicinal properties, as well as their availability and the absence of harmful side effects for most of them. The present study was designed to explore the potential protective effect of curcumin (CUR) and thymoquinone (TQ) in male rats exposed to thioacetamide (TAA). The experimental mice were divided into eight groups. Group 1 was served as control. Group 2 was exposed to 50 mg/ kg body weight of TAA. Group 3 was exposed to CUR and TAA. Mice of group 4 were treated with TQ and TAA. Mice of group 5 were exposed to CUR plus TQ and TAA. Group 6 was supplemented with CUR. Group 7 was subjected to TQ. Mice of group 8 were treated with CUR and TQ. Hematological and biochemical alterations were evaluated after one month. Significant increases of white blood corpuscles (WBC), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total bilirubin (TB), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) values were observed in group 2, while the values of red blood corpuscles (RBC), hemoglobin (Hb(, hematocrit (Hct), glutathione (GSH) and superoxide dismutase (SOD) were statistically decreased. Treatment with CUR, TQ and their combination inhibited the hematological and biochemical alterations induced by TAA toxicity. Moreover, the most protective effect was observed in mice treated with CUR plus TQ. These new results suggested that the protective effect of CUR and TQ attributed to their antioxidant properties.

Sphingolipid imbalance and inflammatory effects induced by uremic toxins in heart and kidney cells are reversed by dihydroceramide desaturase 1 inhibition

Non-dialysable protein-bound uremic toxins (PBUTs) contribute to the development of cardiovascular disease (CVD) in chronic kidney disease (CKD) and vice versa. PBUTs have been shown to alter sphingolipid imbalance. Dihydroceramide desaturase 1 (Des1) is an important gatekeeper enzyme which controls the non-reversible conversion of sphingolipids, dihydroceramide, into ceramide. The present study assessed the effect of Des1 inhibition on PBUT-induced cardiac and renal effects in vitro, using a selective Des1 inhibitor (CIN038). Des1 inhibition attenuated hypertrophy in neonatal rat cardiac myocytes and collagen synthesis in neonatal rat cardiac fibroblasts and renal mesangial cells induced by the PBUTs, indoxyl sulfate and p-cresol sulfate. This is at least attributable to modulation of NF-κB signalling and reductions in β-MHC, Collagen I and TNF-α gene expression. Lipidomic analyses revealed Des1 inhibition restored C16-dihydroceramide levels reduced by indoxyl sulfate. In conclusion, PBUTs play a critical role in mediating sphingolipid imbalance and inflammatory responses in heart and kidney cells, and these effects were attenuated by Des1 inhibition. Therefore, sphingolipid modifying agents may have therapeutic potential for the treatment of CVD and CKD and warrant further investigation.

NF-κB pathway play a role in SCD1 deficiency-induced ceramide de novo synthesis

Stearoyl-CoA-desaturase 1 (SCD1) deficiency mediates apoptosis in colorectal cancer cells by promoting ceramide de novo synthesis. The mechanisms underlying the cross-talk between SCD1 and ceramide synthesis have not been explored. We treated colorectal cancer cells with an SCD1 inhibitor and examined the effects on gene expression, cell growth, and cellular lipid contents. The main effect of SCD1 inhibition on the fatty acid contents of colorectal cancer cells was a decrease in monounsaturated fatty acids (MUFAs). RNA sequencing (RNA-seq) showed that the most intense alteration of gene expression after SCD1 inhibition occurred in the NF-κB signaling pathway. Further experiments revealed that SCD1 inhibition resulted in increased levels of phosphorylated NF-κB p65 and increased nuclear translocation of NF-κB p65. Treatment with an NF-κB inhibitor eliminated several effects of SCD1 inhibition, mainly including overexpression of serine palmitoyltransferase1 (SPT1), elevation of dihydroceramide contents, and suppression of cell growth. Furthermore, treatment with supplemental oleate counteracted the SCD1-induced NF-κB activation and downstream effects. In summary, our data demonstrate that the NF-κB pathway plays a role in SCD1 deficiency-induced ceramide de novo synthesis in colorectal cancer cells, and that reduced MUFA levels contribute to the course.