Caspase Inhibition Prevents Tumor Necrosis Factor-α–Induced Apoptosis and Promotes Necrotic Cell Death in Mouse Hepatocytes in Vivo and in Vitro

Abstract

How different cell death modes and cell survival pathways cross talk remains elusive. We determined the interrelation of apoptosis, necrosis, and autophagy in tumor necrosis factor (TNF)-a/actinomycin D (ActD) and lipopolysaccharide/D-galactosamine (GalN)-induced hepatotoxicity in vitro and in vivo. We found that TNF-a/ActD-induced apoptosis was completely blocked by a general caspase inhibitor ZVADfmk at 24 hours but hepatocytes still died by necrosis at 48 hours. Inhibition of caspases also protected mice against lipopolysaccharide/GalN-induced apoptosis and liver injury at the early time point, but this protection was diminished after prolonged treatment by switching apoptosis to necrosis. Inhibition of receptor-interacting protein kinase (RIP)1 by necrostatin 1 partially inhibited TNF-a/ZVAD-induced necrosis in primary hepatocytes. Pharmacologic inhibition of autophagy or genetic deletion of Atg5 in hepatocytes did not protect against TNF-a/ActD/ZVAD-induced necrosis. Moreover, pharmacologic inhibition of RIP1 or genetic deletion of RIP3 failed to protect and even exacerbated liver injury after mice were treated with lipopolysaccharide/GalN and a pan-caspase inhibitor. In conclusion, our results suggest that different cell death mode and cell survival pathways are closely integrated during TNF-ae induced liver injury when both caspases and NF-kB are blocked. Moreover, results from our study also raised concerns about the safety of currently ongoing clinical trials that use caspase inhibitors. (Am J Pathol 2016 http://dx

Caspase inhibitors for the treatment of liver disease: friend or foe?

“…Consistent with previous reports, treatment of mice with a pan-caspase inhibitor effectively protected against apoptosis during the early injury phase in the galactosamine/endotoxin model, but even with this sustained inhibition of caspase activity, cells eventually undergo massive necrosis 24 hours after the initial treatment [22]. Although caspase inhibition prevented RIP1 and RIP3 degradation, this cell death was independent of traditional necroptosis.…”

“…Although caspase inhibition prevented RIP1 and RIP3 degradation, this cell death was independent of traditional necroptosis. Both RIP3-deficient mice and wild type animals treated with the RIP1 inhibitor necrostatin-1 were not protected and had a poorer inflammatory profile, indicating that activation of the TNF-α pathway may have additional mechanisms of injury in vivo that also escape caspase inhibition [22]. These findings clearly demonstrate differential effects of caspase inhibitors when used short-term versus more long-term or even chronically.…”

Hepatic neuregulin 4 signaling defines an endocrine checkpoint for steatosis-to-NASH progression

“…Th17 cells gen, whereas the downregulated cluster was enriched for genes involved in lipid metabolism ( Figure 2E). Consistently, mRNA expression of genes involved in liver fibrosis, including Col1a1, Acta2, Tgfb1, and Mmp13, and hepatic inflammation, including Previous studies have demonstrated that treatments of primary hepatocytes with a combination of palmitic acid (PA) and TNF-α (PA/TNF-α) robustly triggered cell death that mimics NASHinduced liver injury (21,37). To investigate whether Nrg4 plays a direct role in the regulation of hepatocyte death, we treated primary hepatocytes transduced with GFP or ErbB4 adenovirus with PA/TNF-α.…”

Stellate Cells Orchestrate Concanavalin A–Induced Acute Liver Damage

“…These data agree with an earlier report showing caspase-3—independent hepatocyte necrosis as the predominant mechanism of ConA-induced liver damage in vivo . 39 Although several TUNEL-positive hepatocytes found in ConA-treated mice might suggest involvement of other caspases, as significant inhibition of ConA-induced apoptosis was observed by blocker of caspase-1—like protease YVADcmk, 46 a recent report by Ni et al 47 demonstrated that TUNEL-positive cells could be either apoptotic or necrotic. Because ConA-treated HSCs induced apoptosis but not necrosis in vitro (Figure 5 and Supplemental Figure S8), it is conceivable that the caspase cascade is activated earlier after ConA challenge in vivo , and with increased generation of mediators of cell damage by infiltrating cells and ATP depletion, necrosis predominates as a major mechanism of cell death.…”