Lysophosphatidic Acid signals through specific lysophosphatidic Acid receptor subtypes to control key regenerative responses of human gingival and periodontal ligament fibroblasts.

BACKGROUND: We showed that the pluripotent platelet growth factor and mediator lysophosphatidic acid (LPA) controls key regenerative responses of human gingival fibroblasts (GFs) and periodontal ligament fibroblasts (PDLFs) and positively modulates their responses to platelet-derived growth factor (PDGF). This study determined which LPA receptor (LPAR) subtype(s) LPA signals through to stimulate mitogenic extracellular signal-regulated kinase (ERK) 1/2 signaling and chemotaxis and to elicit intracellular Ca(2+) increases in GFs and PDLFs because many healing responses are calcium-dependent. METHODS: Activation of mitogen-activated protein kinase was determined using Western blotting with an antibody to phosphorylated ERK1/2. Migration responses were measured using a microchemotaxis chamber. GF and PDLF intracellular Ca(2+) mobilization responses to multiple LPA species and LPAR subtype-specific agonists were measured by using a cell-permeable fluorescent Ca(2+) indicator dye. RESULTS: LPA stimulated ERK1/2 phosphorylation via LPA(1)(-3). For GFs, LPA(1) preferentially elicited chemotaxis, and LPA(1-3) for PDLFs, as confirmed using subtype-specific agonists. Elevation of intracellular calcium seems to be mediated through LPA(1) and LPA(3), with little, if any, contribution from LPA(2). CONCLUSIONS: To the best of our knowledge, this study provides the first evidence that LPA signals through specific LPAR subtypes to stimulate human oral fibroblast regenerative responses. These data, in conjunction with our previous findings showing that LPA modulates GF and PDLF responses to PDGF, suggest that LPA is a factor of emerging importance to oral wound healing.

A Major Human Oral Lysophosphatidic Acid Species, LPA 18:1, Regulates Novel Genes in Human Gingival Fibroblasts.

BACKGROUND: The small bioactive lipid lysophosphatidic acid (LPA) plays critical roles in both normal physiology and inflammation in many systems. However, its actions are just beginning to be defined in oral biology and pathophysiology. METHODS: Microarray analysis was used to test the hypothesis that human gingival fibroblasts (GFs) would show significant changes in wound-healing and inflammation-related gene transcripts in response to a major human salivary and gingival crevicular fluid LPA species, 18:1, and that they would express transcript for the major LPA-producing enzyme autotaxin. The microarray results were validated for three highly relevant upregulated inflammatory transcripts using quantitative reverse transcription-polymerase chain reaction (QRT-PCR). Liquid chromatography-tandem mass spectrometry was used to assay time-dependent LPA species production by GFs. RESULTS: LPA 18:1 significantly regulated 20 GF novel and 27 known genes linked to the control of inflammation (P ≤0.01). QRT-PCR validation of interleukin (IL)-8, IL-11, and suppressor of cytokine signaling 2 (SOCS2) messenger RNAs confirmed statistically significant differences from control (P ≤0.05). Autotaxin transcript was present, and GFs were found to produce multiple LPA species in a time-dependent manner. CONCLUSIONS: The upregulation of transcripts for known GF proinflammatory (IL-6, IL-8) and anti-inflammatory (IL-11) ILs, along with SOCS2, shows that LPA transiently regulates a complex set of GF genes critical to periodontal wound healing and inflammation. These results implicate LPA exerting actions on GFs that are compatible with functioning as a mediator in oral fibroblast biology and inflammatory responses. Therefore, LPA may potentially modulate/regulate periodontal inflammation.