Abstract
Periodontitis is a disease of ageing or inflammaging, and is comorbid with other more severe age-related chronic diseases. With advanced age comes an increase in accumulation of senescent cells that release soluble and insoluble pro-inflammatory factors collectively termed the senescence associated secretory phenotype (SASP). In the present report, we examined whether immune cells typical of those at the oral mucosa-microbe interface, are vulnerable to cellular senescence (CS) and the role of dysbiotic oral pathogen Porphyromonas gingivalis. Bone marrow-derived dendritic cells (DCs) from young (yDCs) and old (oDCs) mice were co-cultured in vitro with CS inducer doxorubicin or P.gingivalis (Pg), plus or minus senolytic agent rapamycin. CS profiling revealed elevated CS mediators SA-β-Gal, p16 INK4A, p53, and p21Waf1/Clip1 in oDCs, or yDCs in response to doxorubicin or P. gingivalis, reversible with rapamycin. Functional studies indicate impaired maturation function of oDCs, and yDC exposed to P. gingivalis; moreover, OVA-driven proliferation of CD4+ T cells from young OTII transgenic mice was impaired by oDCs or yDCs+Pg. The SASP of DCs, consisting of secreted exosomes and inflammasome-related cytokines was further analyzed. Exosomes of DCs cocultured with P. gingivalis (PgDCexo) were purified, quantitated and characterized. Though typical in terms of size, shape and phenotype, PgDCexo were 2-fold greater in number than control DCs, with several important distinctions. Namely, PgDCexo were enriched in age-related miRNAs, and miRNAs reported to disrupt immune homeostasis through negative regulation of apoptosis and autophagy functions. We further show that PgDCexo were enriched in P. gingivalis fimbrial adhesin protein mfa1 and in inflammasome related cytokines IL-1β, TNFα and IL-6. Functionally PgDCexo were readily endocytosed by recipient yDCs, amplifying functional impairment in maturation and ability to promote Ova-driven proliferation of OTII CD4+ T cells from young mice. In conclusion P. gingivalis induces premature (autocrine) senescence in DCs by direct cellular invasion and greatly amplifies senescence, in paracrine, of bystander DCs by secretion of inflammatory exosomes. The implications of this pathological pathway for periodontal disease in vivo is under investigation in mouse models.
Highlights
Periodontitis (PD) in adults is a chronic inflammatory disease of ageing or inflammaging (Ebersole et al, 2018; Qin et al, 2020)
Both P. gingivalis and doxorubicin stimulated an increase in p16 INK4A, p53 and p21Waf1/Clip1 in yDCs (Figures 1A, B). oDCs had a trend towards constitutively higher levels of senescence markers than yDCs shown by immunoblot analysis of induced p16 INK4A, p53 and p21Waf1/Clip1,it only reached significance level in P53 upregulation
P.gingivalis LPS induced increased expression of p53 and p21Waf1/Clip1, but not p16 INK4A and SA-bGal in yDCs compared to control yDCs with no infection
Summary
Periodontitis (PD) in adults is a chronic inflammatory disease of ageing or inflammaging (Ebersole et al, 2018; Qin et al, 2020). P. gingivalis induces a dysbiosis by disruption of innate immunity, wherein symbiotic commensals become accessory pathogens (Hajishengallis et al, 2011; Hajishengallis et al, 2012; Dutzan et al, 2018) through unclear mechanisms. The antigen presenting cells dendritic cells (DCs), responsible for bridging innate and adaptive immunity, infiltrate the gingiva in PD (Jotwani et al, 2001; Jotwani and Cutler, 2003; Jotwani et al, 2003; Jotwani et al, 2004), where P. gingivalis and other microbes are taken up in vivo (Carrion et al, 2012; El-Awady et al, 2019; Rajendran et al, 2019). Hyperactivation of Akt and antiapoptotic pathways (Meghil et al, 2019) have recently been linked to premature cellular senescence (CS) (Nogueira et al, 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
