Gastrointestinal Inflammation and Repair: Role of Microbiome, Infection, and Nutrition

Gastrointestinal inflammation is a complex biological response to injury as a result of different stimuli such as pathogens, damaged cells, or irritants. Symbiotic microbiome in digestive tract is considered to protect gut by removing harmful stimuli and to enhance healing process. Alteration or absence of microbiome can lead to exacerbated type 2 immunity and allergic/infectious and inflammatory complications including parasitic diseases. Thus, the microbiota regulates type 2 responses and acts as a key element in harmonizing immune responses at mucosal surfaces. While the mechanism by which microbiota regulates type 2 immunity is unclear, it is known as a strong inducer of proinflammatory T helper 17 cells and regulatory T cells (Tregs) in the intestine.The signals at the sites of inflammation mediate rapid cell recruitment and differentiation in order to remove inflammatory inducers and promote tissue homeostasis restoration.However, persistent inflammatory stimuli or dysregulation of mechanisms of the restoration can lead to chronic inflammation. Different stressors can affect immune system and increase risk for infectious diseases, such as gastritis in postinfectious irritable bowel syndrome (IBS), and vice versa, as IBS patients have increased susceptibility to develop infectious gastroenteritis. Various viral (e.g., norovirus), microbial (e.g., Campylobacter jejuni, Clostridium, Mycobacterium), and parasitic agents (e.g., Giardia, helminthes) are known to be involved in the development of chronic inflammatory bowel diseases. Yet, the mechanisms of action are not well known and there is no available cure. Additionally, nutritional elements, such as n-3 polyunsaturated fatty acids, antioxidants, probiotics, and prebiotics directly and indirectly modulate GI immunity. Diets high in fat change the populations of innate microbiome in digestive tract and alter signaling to the brain and satiety, leading to obesity and inflammation.