Despite the extensive research on Notch signaling involvement in inflammation, its role in macrophage response in autoimmune diseases and defense mechanisms against bacterial infection such as Mycobacterium avium paratuberculosis (MAP) remains unknown. In this study, we investigated the molecular role of Notch-1 signaling and its downstream modulation in the macrophage response during infection and disease treatment. We demonstrated that MAP infection significantly upregulated Notch-1 and IL-6, which hijacked myeloid cell leukemia sequence-1 (MCL)-1 dependent inhibition of apoptosis and caused chronic MAP persistence and significantly led to successive inflammation. Blocking Notch signaling with gamma-secretase inhibitor (DAPT) decreased MAP survival and burden, increased apoptosis, and diminished the pro-inflammatory response. We have also unmasked the mechanism involved in Notch-1 signaling in response to anti-TNF-Alpha therapeutics. Anti-TNF-Alpha induced Notch-1 signaling in macrophages and consequently upregulated IL-6 and MCL-1, increased intracellular MAP Infection, and further inflammation. This may explain the short-term benefits and poor response to anti-TNF-Alpha therapy in most patients. Furthermore, we reported that polymorphisms in microRNA (miR)-146a rs2910164 GC occurs significantly in Crohn's disease leading to loss of miR-146a function and appears to upregulate Notch-1/IL-6 signaling and further worsens MAP infection and inflammation in patients. We were intrigued by the fact that the majority of fatalities of Coronavirus disease 2019 (COVID-19) were among patients with underlying conditions, including those with autoimmune diseases, many of whom were on anti-TNF-a therapy. In this study, we discovered that anti-TNF-Alpha therapy is involved in acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cellular entry and COVID-19 severe complications. Specifically, we found that anti-TNF-a monoclonal antibodies (Humira) via Notch-1/IL-6 signaling modulate TNF-a converting enzyme (TACE) signaling and angiotensin-converting enzyme II (ACE2) expression and its extracellular shedding by increasing type II transmembrane serine proteases (TMPRSS2)/TACE ratio; a high circulating ACE2 level is protective against viral infection. Clinically, ACE2 level was significantly lower in the plasma from RA patients on anti-TNF-Alpha treatment compared to healthy controls in our study. More follow up studies are needed to validate the safety of anti-TNF-Alpha therapy in high risk populations during the COVID-19 Pandemic. Overall, our data clearly demonstrate the significant importance of Notch-1/IL-6 signaling in macrophage response to infection and therapeutics especially in patients with underlying conditions.
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Doctor of Philosophy (Ph.D.)
College of Medicine
Burnett School of Biomedical Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
College of Medicine
Keewan, Esra'a, "The Role of Notch1, IL-6 and miR-146a in Inflammation and Infection in Crohn's Disease Non-Responders to Anti-TNF-Alpha Therapy" (2020). Electronic Theses and Dissertations, 2020-. 805.