Air pollution is one of the most important environmental issues in China and worldwide, as well as a critical public health problem affecting human health. With the implementation of emission reduction and other programs, the air quality in China has been improved dramatically in recent years, but is still worse than the WHO guideline recommended levels. Numerous epidemiological and toxicological studies have shown that short-term or long-term exposure to air pollution is strongly associated with respiratory diseases, cardiovascular diseases, diabetes, and so forth, in which interleukin-6 (IL-6), a well-known inflammatory factor, may play an important role. Studies have found that IL-6 can bind to interleukin-6 receptor (IL-6R) , which leads to the recruiting and activation of glycoprotein 130, and then the formed IL-6/IL-6R/gp130 complex triggers the janus kinase/signal transducer and activator of transcription, Src homology-2 domain-containing protein tyrosine phosphatase-2/mitogen-activated protein kinase, and phosphatidylinositol 3-kinase/protein kinase B signaling pathways. All of these signaling pathways are found to be involved in a variety of physiopathological processes. In the present review, information about the IL-6 signaling pathway and its role in air pollution-induced adverse health effects was systematically reviewed, hoping to provide insights for the future prevention and control policies.

Fine particulate matter (PM_2.5) is a critical environmental factor that currently affects human health. It primarily enters the body through inhalation and can induce adverse health effects in multiple systems, including respiratory, cardiovascular, nervous, and digestive systems. The homeostasis of gut microbiota is crucial for human health, and gut microbiota may exert multiple effects through the regulation of immune function, metabolic balance, and neural signal transmission. Recently, more and more studies have indicated that exposure to PM_2.5 may alter the composition and richness of gut microbiota and play a crucial role in the development and progression of various diseases through multiple pathways. Given the close interaction between PM_2.5 exposure and gut microbiota, we comprehensively reviewed the effects of ambient PM_2.5 exposure on gut microbiota and the potential underlying mechanisms based on existing epidemiological and toxicological studies. Additionally, the role of gut microbiota in the adverse health effects induced by PM_2.5 exposure, particularly in the context of gut-lung, gut-brain and gut-liver axis were also explored here.