Biology subjects

Thadathil, N.

Publications and source records attributed to Thadathil, N..

3 recordsLinked to original sources

bioRxiv2021

Necroptosis contributes to chronic inflammation and fibrosis in aging liver

Inflammaging, characterized by an increase in low-grade chronic inflammation with age, is a hallmark of aging and is strongly associated with various age-related diseases, including chronic liver disease (CLD) and hepatocellular carcinoma (HCC). Because necroptosis is a cell death pathway that induces inflammation through the release of DAMPs, we tested the hypothesis that age-associated increase in necroptosis contributes to chronic inflammation in aging liver. Phosphorylation of MLKL and MLKL-oligomers, markers of necroptosis, as well as phosphorylation of RIPK3 and RIPK1 were significantly upregulated in the livers of old mice relative to young mice and this increase occurred in the later half of life (i.e., after 18 months of age). Markers of M1 macrophages, expression of proinflammatory cytokines (TNF, IL6 and IL-1{beta}), and markers of fibrosis were significantly upregulated in the liver with age and the change in necroptosis paralleled the changes in inflammation and fibrosis. Hepatocytes and liver macrophages isolated from old mice showed elevated levels of necroptosis markers as well as increased expression of proinflammatory cytokines relative to young mice. Short term treatment with the necroptosis inhibitor, necrostatin-1s (Nec-1s), reduced necroptosis, markers of M1 macrophages, expression of proinflammatory cytokines, and markers of fibrosis in the livers of old mice. Thus, our data show for the first time that liver aging is associated with increased necroptosis and necroptosis contributes to chronic inflammation in the liver, which in turn appears to contribute to liver fibrosis and possibly CLD. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/460953v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@15ab761org.highwire.dtl.DTLVardef@bd7336org.highwire.dtl.DTLVardef@1d6e3bcorg.highwire.dtl.DTLVardef@10159eb_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2021

Necroptosis increases with age in the brain and contributes to age-related neuroinflammation

Chronic inflammation of the central nervous system (CNS), termed neuroinflammation, is a hallmark of aging and a proposed mediator of cognitive decline associated with aging. Neuroinflammation is characterized by the persistent activation of microglia, the innate immune cells of the CNS, with damage-associated molecular patterns (DAMPs) being one of the well-known activators of microglia. Because necroptosis is a cell death pathway that induce inflammation through the release of DAMPs, we hypothesized that an age-associated increase in necroptosis contributes to increased neuroinflammation with age. The marker of necroptosis, phosphorylated form of MLKL (P-MLKL), and kinases in the necroptosis pathway (RIPK1, RIPK3, and MLKL) showed a region-specific increase in the brain with age, specifically in the cortex layer V and the CA3 region of the hippocampus of mice. Similarly, MLKL-oligomers, which causes membrane binding and permeabilization were significantly increased in the cortex and hippocampus of old mice relative to young mice. Nearly 70 to 80% of P-MLKL immunoreactivity was localized to neurons and less than 10% was localized to microglia, whereas no P-MLKL was detected in astrocytes. P-MLKL expression in neurons was detected in the soma, not in the processes. Blocking necroptosis using Mlkl-/- mice reduced markers (Iba-1 and GFAP) of neuroinflammation in the brains of old mice and short-term treatment with the necroptosis inhibitor, necrostatin-1s, reduced expression of proinflammatory cytokines, IL-6 and IL-1{beta}, in the hippocampus of old mice. Thus, our data demonstrate for the first time that brain necroptosis increases with age and contributes to age-related neuroinflammation in mice.

neuroscience↗

bioRxiv2020

Role of necroptosis in chronic hepatic inflammation and liver disease in Cu/Zn superoxide dismutase deficient mice

Mice deficient in the antioxidant enzyme Cu/Zn-superoxide dismutase (Sod1-/- or Sod1KO mice) develop spontaneous hepatocellular carcinoma (HCC) with age. Similar to humans, HCC development in Sod1KO mice progresses from fatty liver disease to non-alcoholic steatohepatitis (NASH) with fibrosis, which eventually progresses to HCC. Because liver inflammation is the main mechanism that drives the disease progression in chronic liver disease (CLD) and because necroptosis is a major source of inflammation, we tested the hypothesis that increased necroptosis in the liver plays a role in increased inflammation and progression to fibrosis and HCC in Sod1KO mice. Phosphorylation of MLKL (P-MLKL), a well-accepted marker of necroptosis, and expression of MLKL protein were significantly increased in the livers of Sod1KO mice compared to WT mice indicating increased necroptosis. Similarly, phosphorylation of RIPK3 and RIPK3 protein levels were also significantly increased. Markers of pro-inflammatory M1 macrophages, NLRP3 inflammasome, and transcript levels of pro-inflammatory cytokines and chemokines, e.g., TNF, IL-6, IL-1{beta}, and Ccl2 that are associated with human NASH and HCC, were significantly increased. Markers of fibrosis and oncogenic transcription factor STAT3 were also upregulated in the livers of Sod1KO mice. Short term treatment of Sod1KO mice with necrostatin-1s (Nec-1s), a necroptosis inhibitor, significantly reduced necroptosis, pro-inflammatory cytokines, fibrosis markers and STAT3 activation. Our data show for the first time that necroptosis-mediated inflammation contributes to fibrosis and HCC progression in Sod1KO mice, a mouse model of accelerated aging and progressive HCC development. These findings suggest that necroptosis might be a target for treating NASH and HCC.

biochemistry↗