Aggregatibacter actinomycetemcomitans Induces Autophagy in Human Junctional Epithelium Keratinocytes

Abstract

The adverse environmental conditions found in the periodontium during periodontitis pathogenesis stimulate local autophagy responses, mainly due to a continuous inflammatory response against the dysbiotic subgingival microbiome. The junctional epithelium represents the main site of the initial interaction between the host and the dysbiotic biofilm. Here, we investigated the role of autophagy in junctional epithelium keratinocytes (JEKs) in response to Aggregatibacter actinomycetemcomitans or its purified lipopolysaccharides (LPS). Immunofluorescence confocal analysis revealed an extensive nuclear translocation of transcription factor EB (TFEB) and consequently, an increase in autophagy markers and LC3-turnover assessed by immunoblotting and qRT-PCR. Correspondingly, challenged JEKs showed a punctuate cytosolic profile of LC3 protein contrasting with the diffuse distribution observed in untreated controls. Three-dimensional reconstructions of confocal images displayed a close association between intracellular bacteria and LC3-positive vesicles. Similarly, a close association between autophagic vesicles and the protein p62 was observed in challenged JEKs, indicating that p62 is the main adapter protein recruited during A. actinomycetemcomitans infection. Finally, the pharmacological inhibition of autophagy significantly increased the number of bacteria-infected cells as well as their death, similar to treatment with LPS. Our results indicate that A. actinomycetemcomitans infection induces autophagy in JEKs, and this homeostatic process has a cytoprotective effect on the host cells during the early stages of infection.

Yunnan Baiyao Might Mitigate Periodontitis Bone Destruction by Inhibiting Autophagy and Promoting Osteoblast Differentiation in vivo, ex vivo and in vitro

“…20 In addition, the junctional epithelium migrates apically resulting in the formation of a deep periodontal pocket as periodontitis advances. 25 YNBY improved the attachment site of the newly formed junctional epithelium and the renewal of the underlying connective tissue. In addition, the shape of the dental papilla was partially restored, indicating that YNBY exhibits positive effects on alveolar bone regeneration and soft tissue healing.…”

Incomplete autophagy promotes the proliferation of Mycoplasma hyopneumoniae through the JNK and Akt pathways in porcine alveolar macrophages

“…As an innate immune response mechanism, autophagy has been shown to be involved in the elimination of some intracellular pathogens, such as Salmonella Typhimurium [ 25 ], Mycobacterium tuberculosis [ 26 ], and Aggregatibacter actinomycetemcomitans [ 27 ]. However, studies have shown that some pathogens have evolved molecular strategies to manipulate the autophagic process for their own benefit.…”

Autophagy as a potential mechanism underlying the biological effect of 1,25-Dihydroxyvitamin D3 on periodontitis: a narrative review

“…The antibacterial effect of 1,25D3 greatly decreased after autophagy inhibition with 3-methyladenine (3-MA) treatment [ 65 ]. A. actinomycetemcomitans infection induced autophagy in human junctional epithelium keratinocytes (JEKs); this process inhibits the intracellular survival of the bacteria and significantly reduces the number of JEKs undergoing cell death [ 77 ]. 1,25D3 treatment enhances antibacterial activity to decrease the number of viable colonies of A. actinomycetemcomitans in cultured GEC [ 19 ].…”