Background Little is known about chronic cannabis smoking-associated oral microbiome and its effects on central nervous system (CNS) functions.
Results In the current study, we have analyzed the saliva microbiome in individuals who chronically smoked cannabis with cannabis use disorder and in non-smoking controls. We found that cannabis smoking in humans was associated with oral microbial dysbiosis. The most increased oral bacteria were Streptococcus and Actinomyces genus and the most decreased bacteria were Neisseria genus in chronic cannabis smokers compared to those in non-smokers. To investigate the function of cannabis use-associated microbiome, mice were orally exposured to Actinomyces. meyeri, Actinomyces. odontolyticus, or Neisseria. elongate through oral gavage twice per week for six months which mimics human conditions. Strikingly, oral exposure of Actinomyces meyeri, an oral pathobiont, but not the other two control bactreria, decreased global activity and increased β-amyloid 42 protein production in the mouse brains.
Conclusions This is the first study to reveal that cannabis-associated enrichment of Actinomyces meyeri may contribute to a hallmark of neuropathology.