Effects of Alcohol and Adenylyl Cyclase Type 7 on Innate Immune System

Abstract

Excessive alcohol consumption is a significant health risk for chronic diseases and injuries. Clinical and experimental evidence indicates that alcohol use causes various abnormalities in the immune system and compromises immune functions. However, the mechanisms of ethanol’s effects on the immune system are not fully understood. Cyclic AMP is a second massager that regulates immune responses. Adenylyl cyclase (AC) is the enzyme that converts ATP to cAMP. Earlier research indicated that type 7 AC (AC7) regulates immune system and is highly responsive to ethanol. Therefore, we hypothesized that AC7 is a central player in regulating alcohol effects on immune responses. In order to elucidate this hypothesis, we have three objectives: 1) examine and compare the immune functions and responses of wild type (WT) and AC7 knockout (KO) microglial cell line, BV-2, in vitro; 2) examine and compare the effects of acute ethanol treatment and myeloid lineage-specific AC7 KO on the LPS-induced inflammation in vivo; 3) examine and compare the effects of chronic ethanol treatment and myeloid lineage-specific AC7 KO on the LPS-induced inflammation in vivo. To carry out these objectives, we generated biallelic AC7 KO microglial BV-2 cells to examine the role of AC7 in the ethanol effect on the immunological functions of macrophages. We also employed myeloid lineage-specific AC7 KO mice to examine acute and chronic ethanol effects on LPS-induced inflammation. Our results have demonstrated that as a dominant AC isoform in BV-2 cells, AC7 is a critical factor that regulates macrophage activation, phagocytosis, and bacterial killing. Ethanol consumption and myeloid lineage-specific AC7 deficiency alter immune responses of LPSchallenged mice. Acute ethanol exposure regulated the expression/secretion of cytokines (GCSF, IL-1β, and TNFα) and chemokines (KC, MIP-1β, MIP-2, IP-10) via AC7-mediated xi signaling. Chronic ethanol treatment mitigates AC7 KO mice from LPS-induced mortality and aggravates direct LPS-induced acute lung injury by enhancing cytokine/chemokine expression and leukocytes recruitment. Chronic ethanol exposure regulated the expression/secretion of GMCSF, IL-1β, IL-6, TNFα, KC, MIP-1α, MIP-1β, and IP-10 via AC7-mediated signaling. Overall, the results of this study suggest that AC7 plays an important role in regulating alcohol effects on LPS-induced immune responses.