Summary The coronavirus disease 2019 (Covid‐19) is a viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) that clinically affects multiple organs of the human body. Cells in the oral cavity express viral entry receptor angiotensin‐converting enzyme 2 that allows viral replication and may cause tissue inflammation and destruction. Recent studies have reported that Covid‐19 patients present oral manifestations with multiple clinical aspects. In this review, we aim to summarise main signs and symptoms of Covid‐19 in the oral cavity, its possible association with oral diseases, and the plausible underlying mechanisms of hyperinflammation reflecting crosstalk between Covid‐19 and oral diseases. Ulcers, blisters, necrotising gingivitis, opportunistic coinfections, salivary gland alterations, white and erythematous plaques and gustatory dysfunction were the most reported clinical oral manifestations in patients with Covid‐19. In general, the lesions appear concomitant with the loss of smell and taste. Multiple reports show evidences of necrotic/ulcerative gingiva, oral blisters and hypergrowth of opportunistic oral pathogens. SARS‐CoV‐2 exhibits tropism for endothelial cells and Covid‐19‐mediated endotheliitis can not only promote inflammation in oral tissues but can also facilitate virus spread. In addition, elevated levels of proinflammatory mediators in patients with Covid‐19 and oral infectious disease can impair tissue homeostasis and cause delayed disease resolution. This suggests potential crosstalk of immune‐mediated pathways underlying pathogenesis. Interestingly, few reports suggest recurrent herpetic lesions and higher bacterial growth in Covid‐19 subjects, indicating SARS‐CoV‐2 and oral virus/bacteria interaction. Larger cohort studies comparing SARS‐CoV‐2 negative and positive subjects will reveal oral manifestation of the virus on oral health and its role in exacerbating oral infection.

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Recent studies have shown the significance of metabolic reprogramming in immune and stromal cell function. Yet, the metabolic reconfiguration of RA macrophages (MΦs) is incompletely understood during active disease and in crosstalk with other cell types in experimental arthritis. This study elucidates a distinct regulation of glycolysis and oxidative phosphorylation in RA MΦs compared to fibroblast (FLS), although PPP is similarly reconfigured in both cell types. 2-DG treatment showed a more robust impact on impairing the RA M1 MΦ-mediated inflammatory phenotype than IACS-010759 (IACS, complexli), by reversing ERK, AKT and STAT1 signaling, IRF8/3 transcription, and CCL2 or CCL5 secretion. This broader inhibitory effect of 2-DG therapy on RA M1 MΦs was linked to dysregulation of glycolysis (GLUT1, PFKFB3, LDHA, lactate) and oxidative PPP (NADP conversion to NADPH), while both compounds were ineffective on oxidative phosphorylation. Distinctly, in RA FLS, 2-DG and IACS therapies constrained LPS/IFNγ-induced AKT & JNK signaling, IRF5/7, and fibrokine expression. Disruption of RA FLS metabolic rewiring by 2-DG or IACS therapy was accompanied by a reduction of glycolysis (HIF1α, PFKFB3) and suppression of citrate or succinate buildup. We found that 2-DG therapy mitigated CIA pathology by intercepting joint F480 + iNOS + MΦ, Vimentin + fibroblast & CD3 + T cell trafficking along with downregulation of IRFs and glycolytic intermediates. Surprisingly, IACS treatment was inconsequential on CIA swelling, cell infiltration, M1 & Th1/Th17 cytokines, and joint glycolytic mediators. Collectively, our results indicate that blockade of glycolysis is more effective than inhibition of complexl in CIA, in part due to its effectiveness on the MΦ inflammatory phenotype.

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The human oral cavity contains a plethora of habitats and tissue environments, such as teeth, tongue, and gingiva, which are home to a rich microbial flora including bacteria, fungi, and viruses. Given the exposed nature of the mouth, oral tissues constantly encounter infectious agents, forming a complex ecological community. In the past, the discussion of microbiological aspects of oral disease has traditionally focused on bacteria and fungi, but viruses are attracting increasing attention as pathogens in oral inflammatory diseases. Therefore, understanding viral prevalence, pathogenicity, and preference regarding oral tissues is critical to understanding the holistic effects of viruses on oral infections. Recent investigations have demonstrated the abundance of certain viruses in oral inflammatory diseases, suggesting an association between viruses and disease. Human herpesviruses are the most extensively studied viruses in different oral inflammatory diseases. However, challenges in viral detection and the lack of reproducible in vitro and in vivo infection models have limited our progress in understanding viruses and their contribution to oral diseases. This review presents a summary of major mammalian viruses and associated diseases in the human oral cavity. The emergence of a recent pathogen SARS-CoV-2 and its tropism for salivary and periodontal tissues further