Pyroptosis: shedding light on the mechanisms and links with cancers

Pyroptosis, a novel form of programmed cell death (PCD) discovered after apoptosis and necrosis, is characterized by cell swelling, cytomembrane perforation and lysis, chromatin DNA fragmentation, and the release of intracellular proinflammatory contents, such as Interleukin (IL) 8, IL-1β, ATP, IL-1α, and high mobility group box 1 (HMGB1). Our understanding of pyroptosis has increased over time with an increase in research on the subject: gasdermin-mediated lytic PCD usually, but not always, requires cleavage by caspases. Moreover, new evidence suggests that pyroptosis induction in tumor cells results in a strong inflammatory response and significant cancer regression, which has stimulated great interest among scientists for its potential application in clinical cancer therapy. It's worth noting that the side effects of chemotherapy and radiotherapy can be triggered by pyroptosis. Thus, the intelligent use of pyroptosis, the double-edged sword for tumors, will enable us to understand the genesis and development of cancers and provide potential methods to develop novel anticancer drugs based on pyroptosis. Hence, in this review, we systematically summarize the molecular mechanisms of pyroptosis and provide the latest available evidence supporting the antitumor properties of pyroptosis, and provide a summary of the various antitumor medicines targeting pyroptosis signaling pathways.

Interleukin-9 attenuates inflammatory response and hepatocyte apoptosis in alcoholic liver injury

Alcoholic liver injury is a liver cell dysfunction disease caused by long-term or excessive alcohol consumption. Inhibiting the production of inflammatory factors is an important way to alleviate liver injury. Interleukin-9 (IL-9) is one of the members of IL-2Rγc family. It has multiple biological functions. Previous studies have shown that IL-9 is a cytokine that is closely related to inflammatory disease, allergic diseases, autoimmune diseases, and parasitic infections. However, no systematic studies have been performed to address the role of IL-9 in ALI. This project aims to investigate the effects of IL-9 on macrophage-related inflammatory response and hepatocyte apoptosis in alcohol-induced liver injury by injecting adeno-associated virus (AAV9) into tail vein. In the ALI model group, western blot and ELISA assays demonstrated that the expression of IL-9 was reduced. Overexpression of IL-9 relieved the injury and reduced the serum levels of IL-6, TNF-α in EtOH-induced ALI mouse model. Moreover, by using western blot, it was indicated that IL-9 can inhibit the expression of pro-apoptotic protein, such as cleaved caspase 3 and Bax. In vitro, mouse recombinant protein IL-9 inhibited the expression of IL-6, TNF-α in EtOH-induced RAW264.7 cells. Moreover, flow cytometry and western blot results displayed that macrophage-derived IL-9 inhibited hepatocyte apoptosis. After silencing STAT3 in AML-12 cells, the anti-apoptotic effect of macrophage-derived IL-9 was further enhanced. These results indicate that IL-9 reduces the production of pro-inflammatory factors in ALI. Furthermore, macrophage-derived IL-9 can reduce hepatocyte apoptosis by inhibiting the activation of the STAT3 pathway.

The miR-455-3p/HDAC2 axis plays a pivotal role in the progression and reversal of liver fibrosis and is regulated by epigenetics

Histone deacetylases (HDACs), especially HDAC2, play a role in alleviating liver fibrosis; however, the specific upstream regulation mechanism is unknown. Herein, TargetScan was used to predict the potential upstream targets of HDAC2, and the role of miR-455-3p was explored. The dual luciferase reporter assay showed that miR-455-3p binds to the 3' UTR of HDAC2 mRNA. Additionally, miR-455-3p was downregulated in the liver tissues of patients with cirrhosis and mice with liver fibrosis, as well as in primary HSCs isolated from fibrotic mouse livers and TGF-β-treated LX-2 cells. In contrast, it is highly expressed in the reversal stage of hepatic fibrosis and MDI-cultured LX-2 cells. Our functional analyses showed that miR-455-3p overexpression facilitated apoptosis and reduced the expression of pro-fibrotic markers and the proliferation of activated LX-2 cells. On the contrary, miR-455-3p inhibition converted inactivated LX-2 cells into activated, proliferative, fibrogenic cells. Interestingly, restoration of HDAC2 expression partially blocked the function of miR-455-3p. Downregulated miR-455-3p expression can be restored by DNA methyltransferases in activated LX-2 cells. Methylation-specific PCR, bisulfite sequencing PCR, and chromatin immunoprecipitation assays indicated that the methylation level of miR-455-3p promoter CpG islands was elevated in TGF-β-treated LX-2 cells and that miR-455-3p was downregulated in activated LX-2 cells by DNA hypermethylation, which is mediated by DNMT3b and DNMT1. In conclusion, miR-455-3p acts as a liver fibrosis suppressor by targeting HDAC2, and its deficiency further aggravates the reversal phase of fibrosis. Thus, the epigenetics mediated miR-455-3p/HDAC2 axis may serve as a novel potential therapeutic target for clinical treatment of hepatic fibrosis.

Methylation of RCAN1.4 mediated by DNMT1 and DNMT3b enhances hepatic stellate cell activation and liver fibrogenesis through Calcineurin/NFAT3 signaling

Background: Liver fibrosis is characterized by extensive deposition of extracellular matrix (ECM) components in the liver. RCAN1 (regulator of calcineurin 1), an endogenous inhibitor of calcineurin (CaN), is required for ECM synthesis during hypertrophy of various organs. However, the functional role of RCAN1 in liver fibrogenesis has not yet been addressed. Methods: We induced experimental liver fibrosis in mice by intraperitoneal injection of 10 % CCl4 twice a week. To investigate the functional role of RCAN1.4 in the progression of liver fibrosis, we specifically over-expressed RCAN1.4 in mice liver using rAAV8-packaged RCAN1.4 over-expression plasmid. Following the establishment of the fibrotic mouse model, primary hepatic stellate cells were isolated. Subsequently, we evaluated the effect of RCAN1.4 on hepatic fibrogenesis, hepatic stellate cell activation, and cell survival. The biological role and signaling events for RCAN1 were analyzed by protein-protein interaction (PPI) network. Bisulfite sequencing PCR (BSP) was used to predict the methylated CpG islands in the RCAN1.4 gene promoter. We used the chromatin immunoprecipitation (ChIP assay) to investigate DNA methyltransferases which induced decreased expression of RCAN1.4 in liver fibrosis. Results: Two isoforms of RCAN1 protein were expressed in CCl4-induced liver fibrosis mouse model and HSC-T6 cells cultured with transforming growth factor-beta 1 (TGF-β1). RCAN1 isoform 4 (RCAN1.4) was selectively down-regulated in vivo and in vitro. The BSP analysis indicated the presence of two methylated sites in RCAN1.4 promoter and the downregulated RCAN1.4 expression levels could be restored by 5-aza-2'-deoxycytidine (5-azadC) and DNMTs-RNAi transfection in vitro. ChIP assay was used to demonstrate that the decreased RCAN1.4 expression was associated with DNMT1 and DNMT3b. Furthermore, we established a CCl4-induced liver fibrosis mouse model by injecting the recombinant adeno-associated virus-packaged RCAN1.4 (rAAV8-RCAN1.4) over-expression plasmid through the tail vein. Liver- specific-over-expression of RAN1.4 led to liver function recovery and alleviated ECM deposition. The key protein (a member of the NFAT family of proteins) identified on PPI network data was analyzed in vivo and in vitro. Our results demonstrated that RCAN1.4 over-expression alleviates, whereas its knockdown exacerbates, TGF-β1-induced liver fibrosis in vitro in a CaN/NFAT3 signaling-dependent manner. Conclusions: RCAN1.4 could alleviate liver fibrosis through inhibition of CaN/NFAT3 signaling, and the anti-fibrosis function of RCAN1.4 could be blocked by DNA methylation mediated by DNMT1 and DNMT3b. Thus, RCAN1.4 may serve as a potential therapeutic target in the treatment of liver fibrosis.

Anaphylactoid reactions during haemodialysis in sheep are associated with bradykinin release

Anaphylactoid reactions have been observed in patients treated with AN69 dialysers and ACE inhibitors. Recently, it has been shown in vitro that AN69 membranes induce the release of high amounts of bradykinin in plasma. To verify the possible role of bradykinin in these shock-like reactions, six sheep were dialysed in a random fashion using AN69 or the new SPAN membrane with and without pretreatment with captopril. All animals were dialysed for 60 min via double-lumen Shaldon catheters. Blood samples were drawn at 0, 5, 10, 15, 30, and 60 min from the venous line. A total of 24 haemodialysis procedures was carried out: group A (n = 6), AN69 without captopril; group B (n = 6), SPAN without captopril; group C (n = 6), AN69 with captopril; group D (n = 6), SPAN with captopril. A significant bradykinin release was observed only in groups A and C, reaching peak values already after 5 min. Animals in group C showed the highest bradykinin values. In four of six animals in group C anaphylactoid reactions with severe hypotension were noted. From this animal model we conclude that dialysis with the AN69 membrane is associated with bradykinin release. Pretreatment with ACE inhibitors results in further increasing bradykinin levels, which lead to anaphylactoid reactions. In contrast, the new SPAN membrane was well tolerated without detectable changes in bradykinin concentrations.