Phosphodiesterase-4 inhibition with rolipram attenuates hepatocellular injury in hyperinflammation in vivo and in vitro without influencing inflammation and HO-1 expression

Bilobalide attenuates lipopolysaccharide‑induced HepG2 cell injury by inhibiting TLR4‑NF‑κB signaling via the PI3K/Akt pathway

Inflammation is involved in the pathological process underlying a number of liver diseases. Bilobalide (BB) is a natural compound from Ginkgo biloba leaves that was recently demonstrated to exert hepatoprotective effects by inhibiting oxidative stress in the liver cancer cell line HepG2. The anti-inflammatory activity of BB has been reported in recent studies. The major objective of the present study was to investigate whether BB could attenuate inflammation-associated cell damage. HepG2 cells were cultured with lipopolysaccharide (LPS) and BB, and cell damage was evaluated by measuring cell viability using MTT assay. The activity of the NF-κB signaling pathway was assessed by measuring the levels of IκBα, NF-κB p65, phosphorylated (p)-IκBα, p-p65, p65 DNA-binding activity and inflammatory cytokines IL-1β, IL-6 and TNF-α. A toll-like receptor (TLR)4 inhibitor (CLI-095) was used to detect the involvement of TLR4 in cell injury caused by LPS. In addition, the PI3K/Akt inhibitor LY294002 was applied to explore the involvement of the PI3K/Akt axis in mediating the effects of BB. The results demonstrated that LPS induced HepG2 cell injury. LPS also elevated the levels of p-IκBα, p-p65, p65 DNA-binding activity and inflammatory cytokines. However, CLI-095 significantly attenuated the LPS-induced cell damage and inhibited the activation of NF-κB signaling. BB also dose-dependently attenuated the LPS-induced cell damage, activation of NF-κB signaling and TLR4 overexpression. Furthermore, it was observed that LY294002 diminished the cytoprotective effects of BB on cell injury, TLR4 expression and NF-κB activation. These findings indicated that BB could attenuate LPS-induced inflammatory injury to HepG2 cells by regulating TLR4-NF-κB signaling.

Wogonin alleviates liver injury in sepsis through Nrf2-mediated NF-κB signalling suppression

Sepsis is a life‐threatening organ dysfunction syndrome, and liver is a susceptible target organ in sepsis, because the activation of inflammatory pathways contributes to septic liver injury. Oxidative stress has been documented to participate in septic liver injury, because it not only directly induces oxidative genotoxicity, but also exacerbates inflammatory pathways to potentiate damage of liver. Therefore, to ameliorate oxidative stress is promising for protecting liver in sepsis. Wogonin is the compound extracted from the medicinal plant Scutellaria baicalensis Geogi and was found to exert therapeutic effects in multiple inflammatory diseases via alleviation of oxidative stress. However, whether wogonin is able to mitigate septic liver injury remains unknown. Herein, we firstly proved that wogonin treatment could improve survival of mice with lipopolysaccharide (LPS)‐ or caecal ligation and puncture (CLP)‐induced sepsis, together with restoration of reduced body temperature and respiratory rate, and suppression of several pro‐inflammatory cytokines in circulation. Then, we found that wogonin effectively alleviated liver injury via potentiation of the anti‐oxidative capacity. To be specific, wogonin activated Nrf2 thereby promoting expressions of anti‐oxidative enzymes including NQO‐1, GST, HO‐1, SOD1 and SOD2 in hepatocytes. Moreover, wogonin‐induced Nrf2 activation could suppress NF‐κB‐regulated up‐regulation of pro‐inflammatory cytokines. Ultimately, we provided in vivo evidence that wogonin activated Nrf2 signalling, potentiated anti‐oxidative enzymes and inhibited NF‐κB‐regulated pro‐inflammatory signalling. Taken together, this study demonstrates that wogonin can be the potential therapeutic agent for alleviating liver injury in sepsis by simultaneously ameliorating oxidative stress and inflammatory response through the activation of Nrf2.

The Metabolic Basis of Immune Dysfunction Following Sepsis and Trauma

Critically ill, severely injured and high-risk surgical patients are vulnerable to secondary infections during hospitalization and after hospital discharge. Studies show that the mitochondrial function and oxidative metabolism of monocytes and macrophages are impaired during sepsis. Alternatively, treatment with microbe-derived ligands, such as monophosphoryl lipid A (MPLA), peptidoglycan, or β-glucan, that interact with toll-like receptors and other pattern recognition receptors on leukocytes induces a state of innate immune memory that confers broad-spectrum resistance to infection with common hospital-acquired pathogens. Priming of macrophages with MPLA, CPG oligodeoxynucleotides (CpG ODN), or β-glucan induces a macrophage metabolic phenotype characterized by mitochondrial biogenesis and increased oxidative metabolism in parallel with increased glycolysis, cell size and granularity, augmented phagocytosis, heightened respiratory burst functions, and more effective killing of microbes. The mitochondrion is a bioenergetic organelle that not only contributes to energy supply, biosynthesis, and cellular redox functions but serves as a platform for regulating innate immunological functions such as production of reactive oxygen species (ROS) and regulatory intermediates. This review will define current knowledge of leukocyte metabolic dysfunction during and after sepsis and trauma. We will further discuss therapeutic strategies that target leukocyte mitochondrial function and might have value in preventing or reversing sepsis- and trauma-induced immune dysfunction.

[Phosphodiesterase 4 inhibition for treatment of endothelial barrier and microcirculation disorders in sepsis]

Sepsis is commonly associated with loss of microvascular endothelial barrier function (capillary leak) and dysfunctional microcirculation, which both promote organ failure. The development of a distinct therapy of impaired endothelial barrier function and disturbed microcirculation is highly relevant because both of these phenomena constitute crucial processes which critically influence the prognosis of patients. Numerous in vivo and in vitro trials over the past years have fostered a better understanding of the pathophysiology of capillary leak. Furthermore, promising data in animal models show that therapeutic modulation of endothelial barrier function and microcirculation can be achieved by stabilizing endothelial cAMP (cyclic adenosine monophosphate) levels followed by activation of Rho-GTPase Rac1, e. g. by phosphodiesterase 4 inhibitors. This review summarizes and discusses recent findings of cellular mechanisms and in vivo trials.

Activation of Myenteric Glia during Acute Inflammation In Vitro and In Vivo

Background

Enteric glial cells (EGCs) are the main constituent of the enteric nervous system and share similarities with astrocytes from the central nervous system including their reactivity to an inflammatory microenvironment. Previous studies on EGC pathophysiology have specifically focused on mucosal glia activation and its contribution to mucosal inflammatory processes observed in the gut of inflammatory bowel disease (IBD) patients. In contrast knowledge is scarce on intestinal inflammation not locally restricted to the mucosa but systemically affecting the intestine and its effect on the overall EGC network.

Methods and Results

In this study, we analyzed the biological effects of a systemic LPS-induced hyperinflammatory insult on overall EGCs in a rat model in vivo, mimicking the clinical situation of systemic inflammation response syndrome (SIRS). Tissues from small and large intestine were removed 4 hours after systemic LPS-injection and analyzed on transcript and protein level. Laser capture microdissection was performed to study plexus-specific gene expression alterations. Upon systemic LPS-injection in vivo we observed a rapid and dramatic activation of Glial Fibrillary Acidic Protein (GFAP)-expressing glia on mRNA level, locally restricted to the myenteric plexus. To study the specific role of the GFAP subpopulation, we established flow cytometry-purified primary glial cell cultures from GFAP promotor-driven EGFP reporter mice. After LPS stimulation, we analyzed cytokine secretion and global gene expression profiles, which were finally implemented in a bioinformatic comparative transcriptome analysis. Enriched GFAP+ glial cells cultured as gliospheres secreted increased levels of prominent inflammatory cytokines upon LPS stimulation. Additionally, a shift in myenteric glial gene expression profile was induced that predominantly affected genes associated with immune response.

Conclusion and Significance

Our findings identify the myenteric GFAP-expressing glial subpopulation as particularly susceptible and responsive to acute systemic inflammation of the gut wall and complement knowledge on glial involvement in mucosal inflammation of the intestine.

Phycocyanobilin accelerates liver regeneration and reduces mortality rate in carbon tetrachloride-induced liver injury mice

AIM: To investigate the hepatoprotective effects of phycocyanobilin (PCB) in reducing hepatic injury and accelerating hepatocyte proliferation following carbon tetrachloride (CCl₄) treatment.

METHODS: C57BL/6 mice were orally administered PCB 100 mg/kg for 4 d after CCl₄ injection, and then the serum and liver tissue of the mice were collected at days 1, 2, 3, 5 and 7 after CCl₄ treatment. A series of evaluations were performed to identify the curative effects on liver injury and recovery. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), albumin and superoxide dismutase (SOD) were detected to indirectly assess the anti-inflammatory effects of PCB. Meanwhile, we detected the expressions of hepatocyte growth factor, transforming growth factor alpha (TGF-α), TGF-β, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), the factors which are associated with inflammation and liver regeneration. The protein expressions of proliferating cell nuclear antigen (PCNA), TNF-α and cytochrome C were detected by western blot. Furthermore, the survival rates were analyzed of mice which were administered a lethal dose of CCl₄ (2.6 mg/kg) with or without PCB.

RESULTS: In our research, PCB showed a strongly anti-inflammatory effect on CCl₄-induced liver injury in mice. The ALT was significantly decreased after CCl₄ treatment from day 1 (P < 0.01) and the AST was significantly decreased from day 2 (P < 0.001). Both albumin and liver SOD were increased from day 2 (P < 0.001 and P < 0.01), but serum SOD levels did not show a significant increase (P > 0.05). PCB protected the structure of liver from the injury by CCl₄. TUNEL assay showed that PCB dramatically reduced the number of apoptotic cells after CCl₄ treatment compared to the control (101.0 ± 25.4 vs 25.7 ± 6.4, P < 0.01). The result of western blotting showed that PCB could increase PCNA expression, decrease TNF-α and cytochrome C expression. Furthermore, data shows that PCB could improve the survival rate of acute liver failure (ALF) mice which were injected with a lethal dose of CCl₄ (60.0% vs 20.0%).

CONCLUSION: Our study indicated that PCB could be an ideal candidate for reversing acute liver injury or ALF.