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Recent studies underscore the role of gut and oral microbiota in influencing neuroinflammation through the microbiota–gut–brain axis, including in Alzheimer's disease (AD). This review aims to provide a comprehensive synthesis of recent findings on the involvement of gut and oral microbiota in the neuroinflammatory processes associated with AD, emphasizing novel insights and therapeutic implications. This review reveals that dysbiosis in AD patients' gut and oral microbiota is linked to heightened peripheral and central inflammatory responses. Specific bacterial taxa, such as Bacteroides and Firmicutes in the gut, as well as Porphyromonas gingivalis in the oral cavity, are notably altered in AD, leading to significant changes in microglial activation and cytokine production. Gut microbiota alterations are associated with increased intestinal permeability, facilitating the translocation of endotoxins like lipopolysaccharides (LPS) into the bloodstream and exacerbating neuroinflammation by activating the brain's toll-like receptor 4 (TLR4) pathways. Furthermore, microbiota-derived metabolites, including short-chain fatty acids (SCFAs) and amyloid peptides, can cross the blood-brain barrier and modulate neuroinflammatory responses. While microbial amyloids may contribute to amyloid-beta aggregation in the brain, certain SCFAs like butyrate exhibit anti-inflammatory properties, suggesting a potential therapeutic avenue to mitigate neuroinflammation. This review not only highlights the critical role of microbiota in AD pathology but also offers a ray of hope by suggesting that modulating gut and oral microbiota could represent a novel therapeutic strategy for reducing neuroinflammation and slowing disease progression. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) patients face different health challenges when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) than the general population, due to both their immunocompromised state and the immunosuppressive therapies they receive. This systematic literature review, which follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) paradigm, explores the interactions between RA and SARS-CoV-2 infection, focusing on immunologic issues, disease management, vaccination, and adverse outcomes. In order to obtain the most relevant information, we systematically reviewed the specific literature from 1 January 2021 to 31 December 2023, based on the PRISMA method, by which we eventually selected 35 eligible articles, to which we added other ISI-indexed studies to enrich our results further. Consequently, we performed a funnel analysis to evaluate the potential for publication bias. Firstly, the data collected revealed the impact of the pandemic on RA diagnoses and the fear of face-to-face medical consultations that delayed adequate treatment. Secondly, cardiovascular and metabolic comorbidities increase the risk of prolonged COVID-19 symptoms, hospitalization, and severe COVID-19 outcomes for RA patients. With respect to immunosuppressive treatment used to control RA, it was observed that glucocorticoids (especially high-dose usage) and Rituximab (RTX) predispose the patients to poor SARS-CoV-2 outcomes, as opposed to Baricitinib and interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) inhibitors. COVID-19 vaccination has proven effective and generally safe for RA patients in some studies, although therapies with Methotrexate (MTX), Abatacept (ABA), and RTX have been associated with impaired vaccine immune response. This systematic literature review brings updated and thorough information with respect to the immunological, clinical, and management of a complex immune-mediated inflammatory disease (IMID) like RA in the setting of COVID-19 and underlines the challenges faced by this group of patients. The lessons learned can be extended beyond the pandemic in shaping a more informed and compassionate healthcare system and offering long-term medical care for patients with RA. [ABSTRACT FROM AUTHOR]