Favipiravir Protects Enterocytes From Cell Death After Inflammatory Storm

Abstract

Over the past years, inflammatory bowel disease (IBD) treatment has become more targeted, anticipating the use of immune-modifying therapies at an earlier stage. During the treatment process prevention and management of viral infections hold significant importance.

The protective role of favipiravir on enterocytes which are affected by inflammation is still unknown. We aim to analyze the effects of favipiravir on enterocytes after an inflammatory condition.

We conducted a 2,5-diphenyl-2H-tetrazolium bromide (MTT) assay to assess the cytotoxicity of favipiravir on intestinal epithelioid cells (IEC-6). To mimic the inflammation model in cell culture conditions, we exposed IEC-6 cells to tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). The cells were categorized into four groups: control, inflammation model, application of favipiravir before inflammation (prophylactic), and application of favipiravir after inflammation (treatment). We assessed the presence and distribution of caspase 1, caspase 3, interleukin 6 (IL6), interleukin 8 (IL8), mixed lineage kinase domain-like protein (MLKL), receptor-interacting protein kinase 1 (RIPK1), and TNF-α using indirect immunoperoxidase staining. TNF-α and IL8 levels were analyzed with enzyme-linked immunosorbent assay (ELISA) in a culture medium.

Caspase 1 was observed to be strong (+++) in the treatment group and weak (+) in the prophylactic group compared to the inflammation group. Caspase 3 was weak (+) in the inflammation group, and it was strong (+++) in the prophylactic and treatment group, the increase in the treatment group was significant. Therefore administering favipiravir before inducing inflammation appears to control the inflammatory caspase pathway in intestinal enterocytes, protecting them from inflammatory responses, while the caspase 3-dependent apoptotic pathway may not be active in enterocytes during inflammation. IL6 and IL8 were negative (-) in control, IL6 was weak (+) in inflammation and favipiravir treated groups; IL8 increased significantly in favipiravir groups compared to control and inflammation groups. Consequently, favipiravir may trigger IL6 release, initiating the inflammatory pathway and potentially enhancing IL8 interactions with other cytokines. TNF-α immunoreactivity was strong (+++) in the inflammation group, while it was moderate (++) in favipiravir-administered groups. MLKL immunoreactivity was strong (+++) in all groups, RIPK1 was weak (+) in control, strong (+++) in the inflammation and treatment group, moderate (++) in the prophylactic group, and the increase in inflammation and treatment group was significant compared to control. Our findings suggest that in the treatment group, necroptosis was triggered by increased MLKL and RIPK1, key players in inflammation and cell death.

After immunocytochemical evaluation, our findings suggest that, after the onset of inflammation, favipiravir may play a role in cell death by increasing necroptosis rather than apoptosis.