Serine dipeptide lipids of Porphyromonas gingivalis inhibit osteoblast differentiation: Relationship to Toll-like receptor 2

Abstract

Porphyromonas gingivalis is a periodontal pathogen strongly associated with loss of attachment and supporting bone for teeth. We have previously shown that the total lipid extract of P. gingivalis inhibits osteoblast differentiation through engagement of Toll-like receptor 2 (TLR2) and that serine dipeptide lipids of P. gingivalis engage both mouse and human TLR2. The purpose of the present investigation was to determine whether these serine lipids inhibit osteoblast differentiation in vitro and in vivo and whether TLR2 engagement is involved. Osteoblasts were obtained from calvaria of wild type or TLR2 knockout mouse pups that also express the Col2.3GFP transgene. Two classes of serine dipeptide lipids, termed Lipid 654 and Lipid 430, were tested. Osteoblast differentiation was monitored by cell GFP fluorescence and osteoblast gene expression and osteoblast function was monitored as von Kossa stained mineral deposits. Osteoblast differentiation and function were evaluated in calvarial cell cultures maintained for 21 days. Lipid 654 significantly inhibited GFP expression, osteoblast gene expression and mineral nodule formation and this inhibition was dependent on TLR2 engagement. Lipid 430 also significantly inhibited GFP expression, osteoblast gene expression and mineral nodule formation but these effects were only partially attributed to engagement of TLR2. More importantly, Lipid 430 stimulated TNF-α and RANKL gene expression in wild type cells but not in TLR2 knockout cells. Finally, osteoblast cultures were observed to hydrolyze Lipid 654 to Lipid 430 and this likely occurs through elevated PLA2 activity in the cultured cells. In conclusion, our results show that serine dipeptide lipids of P. gingivalis inhibit osteoblast differentiation and function at least in part through engagement of TLR2. The Lipid 430 serine class also increased the expression of genes that could increase osteoclast activity. We conclude that Lipid 654 and Lipid 430 have the potential to promote TLR2-dependent bone loss as is reported in experimental periodontitis following oral infection with P. gingivalis. These results also support the conclusion that serine dipeptide lipids are involved in alveolar bone loss in chronic periodontitis.

Branched Fatty Acyl Esters of Hydroxyl Fatty Acids (FAHFAs), Appealing Beneficial Endogenous Fat against Obesity and Type‐2 Diabetes

“…Flavolipin,a na mino acid-containing lipid (Scheme 10) from Flavobacterium meningosepticum, an opportunistic pathogen that causes pneumonia, meningitis, and septicemia in immune-compromised individuals, such as newborn infants and patients with advanced HIV.A lso called, Lipid 654 due to its mass, Flavolipin has been demonstrated to play ar ole in the development of two chronic inflammatoryd iseases, including [32][33][34] periodontal disease and atherosclerosis and significantly inhibited osteoblast gene expression. [35] Mostr ecently, studies have shown that Flavolipin may be implicated in the development of multiple sclerosis. [36] The lipid chain moiety 17 consists in an omega methylated tetradecanoid acid esterified with an omega methylated 3(R)hydroxy-hexadecanoica cid (Scheme 10).…”

Phosphoglycerol dihydroceramide, a distinctive ceramide produced by Porphyromonas gingivalis, promotes RANKL-induced osteoclastogenesis by acting on non-muscle myosin II-A (Myh9), an osteoclast cell fusion regulatory factor

“…While LPS produced by P. gingivalis can promote osteoclastogenesis through binding to TLR4 [26], recent studies revealed that serine dipeptide lipids produced by P. gingivalis can act on TLR2 which, in turn, inhibits osteoblastogenesis [27,28]. On the other hand, lipid A derived from P. gingivalis is contaminated with phosphorylated dihydroceramide lipids which can also stimulate TLR2 [29].…”

Convergent synthesis of a deuterium‐labeled serine dipeptide lipid for analysis of biological samples

“…These agonists are also produced by common oral and intestinal Bacteroidetes , and they are recovered in chronically inflamed human tissues including destructive periodontal disease and atherosclerosis tissues . The most commonly observed serine dipeptide mono‐fatty acid species is composed of 3‐OH iso‐C 17:0 fatty acid moiety may form a 3‐OH ester linkage to a saturated fatty acid, most frequently to iso‐C 15:0 (see 1 ) . Members of the Bacteroidetes phylum comprise a group of commensal organisms recovered in the human oral and intestinal microbiomes.…”

“…2 The most commonly observed serine dipeptide mono-fatty acid species is composed of 3-OH iso-C 17:0 fatty acid moiety may form a 3-OH ester linkage to a saturated fatty acid, most frequently to iso-C 15:0 (see 1). 4 Members of the Bacteroidetes phylum comprise a group of commensal organisms recovered in the human oral and intestinal microbiomes. Oral and intestinal Bacteroidetes organisms have recently been shown to produce novel serine dipeptide lipids identical to those described for specific Flavobacteria.…”