Effect of Ga-Al-As laser irradiation on COX-2 and cPLA2-alpha expression in compressed human periodontal ligament cells

Abstract

Background and objective: Prostaglandin E(2) (PGE(2)), which has bone-resorptive activity, is produced by human periodontal ligament (PDL) cells in response to mechanical stress. We previously reported that low level laser (LLL) irradiation inhibited PGE(2) production in PDL cells in response to mechanical stress; however, the mechanism underlying this inhibitory effect was unclear. Thus, we sought to determine the mechanism underlying the inhibitory effect of LLL on PGE(2) production in compressed PDL cells.

Study design/materials and methods: A compressive force of 2.0 g/cm(2) was applied for 24 hours to human PDL cells obtained from premolars extracted for orthodontic treatment. LLL irradiation (Ga-Al-As laser, 830 nm, 3.82 J/cm(2)) was applied 6 hours before, 1 hour before, and immediately after the application of compressive force. The mRNA expression of COX-2 and cPLA(2)-alpha was then examined by real-time PCR.

Results: LLL irradiation significantly inhibited COX-2 and cPLA(2)-alpha mRNA expression, which was increased in response to the application of a compressive force. Moreover, LLL irradiation immediately after compression had the strongest inhibitory effect on the expression of these genes.

Conclusions: The inhibition of PGE(2) production by LLL irradiation in compressed PDL cells may be due to the inhibition of COX-2 and cPLA(2)-alpha expression and is most pronounced immediately after the application of a compressive force.