Summary
Background HIV/SIV-associated periodontal disease (gingivitis/periodontitis) (PD) represents a major comorbidity
affecting people living with HIV (PLWH) on combination anti-retroviral therapy (cART). PD is characterized by
chronic inflammation and dysbiosis. Nevertheless, the molecular mechanisms and use of feasible therapeutic strategies to reduce/reverse inflammation and dysbiosis remain understudied and unaddressed.
Methods Employing a systems biology approach, we report molecular, metabolome and microbiome changes
underlying PD and its modulation by phytocannabinoids [delta-9-tetrahydrocannabinol (D9
-THC)] in uninfected
and SIV-infected rhesus macaques (RMs) untreated (VEH-untreated/SIV) or treated with vehicle (VEH/SIV) or D9
–
THC (THC/SIV).
Findings VEH- untreated/SIV but not THC/SIV RMs showed significant enrichment of genes linked to anti-viral
defense, interferon-b, NFkB, RIG-1, and JAK-STAT signaling. We focused on the anti-microbial DUOX1 and
immune activation marker IDO1 that were reciprocally regulated in the gingiva of VEH-untreated/SIV RMs. Both
proteins localized to the gingival epithelium and CD163+ macrophages, and showed differential expression in the
gingiva of THC/SIV and VEH/SIV RMs. Additionally, inflammation-associated miR-21, miR-1423p, miR-223, and
miR-125a-5p showed significantly higher expression in the gingiva of VEH/SIV RMs. In human primary gingival
epithelial cells, miR-125a-5p post-transcriptionally downregulated DUOX1 and THC inhibited IDO1 protein expression through a cannabinoid receptor-2 mediated mechanism. Interestingly, THC/SIV RMs showed relatively
reduced plasma levels of kynurenine, kynurenate, and the neurotoxic quinolinate compared to VEH/SIV RMs at 5
months post SIV infection (MPI). Most importantly, THC blocked HIV/SIV-induced depletion of Firmicutes and
Bacteroidetes, and reduced Gammaproteobacteria abundance in saliva. Reduced IDO1 protein expression was associated with significantly (p<0.05) higher abundance of Prevotella, Lactobacillus (L. salivarius, L. buchneri, L. fermentum,
L. paracasei, L. rhamnosus, L. johnsonii) and Bifidobacteria and reduced abundance of the pathogenic Porphyromonas
cangingivalis and Porphyromonas macacae at 5MPI.
Interpretation The data provides deeper insights into the molecular mechanisms underlying HIV/SIV-induced PD
and more importantly, the anti-inflammatory and anti-dysbiotic properties of THC in the oral cavity. Overall, these
translational findings suggest that phytocannabinoids may help reduce gingival/systemic inflammation, salivary
dysbiosis and potentially metabolic disease/syndrome in PLWH on cART and those with no access to cART or do
not suppress the virus under cART
