CD38, a nicotinamide adenine dinucleotide (NAD⁺) glycohydrolase, increases during infection or inflammation. Therefore, we aimed to evaluate the effects of a CD38 inhibitor (78c) on NAD⁺ levels, IL-1β, IL-6, TNF-α cytokine expressions, and osteoclastogenesis. The results show that treatment with 78c on murine BMMs dose-dependently reduced CD38, reversed the decline of NAD⁺, and inhibited IL-1β, IL-6, and TNF-α pro-inflammatory cytokine levels induced by oral pathogen Porphyromonas gingivalis (Pg) or Aggregatibacter actinomycetemcomitans (Aa) or by advanced glycation end products (AGEs). Additionally, treatment with 78c dose-dependently suppressed osteoclastogenesis and bone resorption induced by RANKL. Treatment with 78c suppressed CD38, nuclear factor kappa-B (NF-κB), phosphoinositide 3-kinase (PI3K), and mitogen-activated protein kinases (MAPKs) induced by Pg, Aa, or AGEs, and suppressed podosome components (PI3K, Pyk2, Src, F-actin, integrins, paxillin, and talin) induced by RANKL. These results from our studies support the finding that the inhibition of CD38 by 78c is a promising therapeutic strategy to treat inflammatory bone loss diseases. However, treatment with a CD38 shRNA only significantly reduced IL-1β, IL-6, and TNF-α pro-inflammatory cytokine levels induced by AGEs. Compared with controls, it had limited effects on cytokine levels induced by Pg or Aa. Treatment with the CD38 shRNA enhanced RANKL-induced osteoclastogenesis, suggesting that 78c has some off-target effects.

CD38, a nicotinamide adenine dinucleotide (NAD⁺) glycohydrolase, increases in old murine macrophages after infection compared to young controls. We aimed to determine whether the increase in CD38 in old murine macrophages after infection is directly associated with enhanced inflammation induced by the oral pathogens Aggregatibacter actinomycetemcomitans (Aa) or Porphyromonas gingivalis (Pg) when compared to young controls. Additionally, we determined the effects of a specific CD38 inhibitor (78c) on CD38, NAD⁺, interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α expressions, and anti-oxidative responses in old murine macrophages induced by oral pathogens. Old and young murine macrophages were either uninfected or infected with the oral pathogens Aa or Pg for 1 to 24 h. Protein levels of CD38 and protein kinases, including nuclear factor kappa-B (NF-κB), phosphoinositide 3-kinase (PI3K), and mitogen-activated protein kinases (MAPKs), NAD⁺, and inflammatory cytokine (IL-1β, IL-6, TNF-α) levels were evaluated. Additionally, old murine macrophages were treated with a vehicle or a CD38 inhibitor (78c) and cells were either uninfected or infected with Aa or Pg. CD38, NAD⁺, cytokine (IL-1β, IL-6, TNF-α) levels, reactive oxygen species (ROS), NAPDH oxidase 1 (Nox1), and anti-oxidative enzymes, including superoxide dismutase1 (Sod1), glutathione peroxidase 4 (Gpx4), Peroxiredoxin 1 (Prdx1), thioredoxin reductase 1 (Txnrd1), and catalase (Cat), were evaluated. The results showed that old murine macrophages significantly enhanced CD38 and reduced NAD⁺ levels 24 h after Aa or Pg infection compared to young controls. This enhanced CD38 in old murine macrophages was not directly correlated with the activation of protein kinases (NF-κB, PI3K, and MAPKs), nor the (IL-1β, IL-6, TNF-α) levels in macrophages. The inhibition of CD38 by 78c reduced CD38, enhanced NAD⁺ levels, attenuated IL-1β, IL-6 and TNF-α pro-inflammatory cytokine levels, reduced ROS and Nox1 expressions, and enhanced expressions of Sod1, Gpx4, Prdx1, Txnrd1, and Cat in old murine macrophages infected with Aa or Pg. These results suggest that the inhibition of CD38 by 78c is a promising therapeutic strategy to treat aging-associated periodontitis.

CD38, a nicotinamide adenine dinucleotide (NAD+) glycohydrolase, increases in old murine macrophages after infection compared to young controls. We aimed to determine whether the increase of CD38 in old murine macrophages after infection is directly associated with enhanced inflammation induced by the oral pathogens Aggregatibacter actinomycetemcomitans (Aa) or Porphyromonas gingivalis (Pg) when compared to young controls. Additionally, we determined the effects of a specific CD38 inhibitor (78c) on CD38; NAD+; IL-1, IL-6, TNF- expressions; and anti-oxidative responses in old murine macrophages induced by oral pathogens. Results showed that old murine macrophages significantly enhanced CD38 and reduced NAD+ levels 24 h after Aa or Pg infection compared to young controls. This enhanced CD38 in old murine macrophages was not directly correlated with the degree of inflammation in macrophages. Inhibition of CD38 by 78c reduced CD38, enhanced NAD+ levels, attenuated IL-1b, IL-6, TNF-a proinflammatory cytokine levels, decreased NAPDH oxidase 1 (Nox1) expression, and enhanced expressions of anti-oxidative enzymes [superoxide dismutase1 (Sod1), glutathione peroxidase 4 (Gpx4), Peroxiredoxin 1 (Prdx1), thioredoxin reductase 1 (Txnrd1), and catalase (Cat)] in old murine macrophages infected with Aa or Pg. These results suggest that inhibition of CD38 by 78c is a promising therapeutic strategy to treat aging-associated periodontitis.