Effects of heated tobacco products and conventional cigarettes on oxidative stress and inflammation in alveolar macrophages

Abstract

Oxidative stress in macrophages is a major factor contributing to smoking-induced chronic respiratory diseases. However, the oxidative stress induced by heat-not-burn tobacco products (HTP) and conventional cigarettes (3R4F) in macrophages has not been sufficiently investigated. This study compared the effects of HTP and 3R4F cigarettes on cytotoxicity and oxidative stress. We also investigated the underlying mechanisms of autophagy-induced inflammation in macrophages. Our results showed that both HTP and 3R4F cigarette aerosols induced cytotoxicity; however, HTP aerosol was less cytotoxic than conventional cigarette aerosol in RAW264.7 cells. In addition, both aerosols resulted in increased reactive oxygen species (ROS) levels in RAW 264.7 and bone marrow-derived macrophages (BMMs), although the levels were lower for HTP aerosol than for 3R4F aerosol. Additionally, acute exposure to HTP aerosol elevated the levels of IL-1β, IL-6, and TNF-α in macrophages. Oxidative stress-triggered TFEB oxidation induced TFEB nuclear translocation, thereby enhancing autophagy and inflammation in HTP- and 3R4F-exposed macrophages. In conclusion, our study demonstrated that aerosols from HTP and 3R4F cigarettes increased the cytotoxicity in macrophages. Cigarette aerosols increase oxidative stress, which triggers TFEB oxidation and increases its nuclear translocation. TFEB oxidation leads to increased autophagy and inflammation in HTP- or 3R4F aerosol-exposed macrophages. Exposure to HTP aerosols resulted in lower cytotoxicity, oxidative stress, and inflammatory responses than the exposure to conventional cigarettes in vitro.