Al though the changes in tooth morphology and hardness by hydrogen peroxide(H20 z) have been r‘epor‘.ted .‘ the pαr。o야t뻐ec야tive role of heme oxygenase-l(HO-l) against the cytotoxic effects of H202 has not been clarifïed i n human pulp cells ln this st udy. we investigated whether HO-l is involved in Hz0 2-induced cytoLox icity a nd examined the production 0 1' dentin sia lophosphoprotein(DSPP) and other mineralization markers‘ in hllman pu lp cells H202 decreased cell viabi lity, but increased HO-l and DSPP expression in a concentra tion and time dependent manner . Inhibitors of gllanylate cyclase. PI3K, ERK. and p38 MAP kinase blocked H202-indllced cytotoxicity and the expression of HO-l and DSPP mRNAs in pulp cells. These data suggest that the induction of HO-l by H202 in plllp cells plays a protective role against the cytotoxic effects 0 1' HzOz and stimulates DSPP expression‘ reslllting in prematllre odontoblast dilTerentiation throllgh pathways that involve cGMP‘ p38. and ERK.

Al t hough substance P(SP) , a potent pro- inflammatory peptide, is involved in inflammation and immune responses‘ t he eff'ect of SP on t he expression of macrophage inflammatory protein 3a (MIP- 3α CCL20) in periodontal liga ment(PDL) cell s a re unknown, Equally as enigmatic is the link between SP, t he stress protein heme oxygenase- l(HO-l) ‘ and CCL20 procluction, We investigated whether SP induces the release of chemokine CCL20 from immortal ized PDL(IPDL) ceJJ s‘ and fur ther c l a꺼 SP mediated pathways, We also examined the relationship between HO-l a ncl CCL20 by t reating PDL cells with SP, Incubating IPDL cells with SP increased expression of CCL20 mRNA a nd CCL20 protein in a dose-time dependent manner Highly selective p38 and ERKl/2 inhibitors abrogated SP-induced expression of CCL20 in IPDL cell s, SP is a lso responsible for ini t iating phosphorylation of I/C B, degradation of Iκ B‘ ancl activat ion of NF'-/C B, SP induced expression of HO-l in both a concentration- and time-dependent man nel ‘ and CCL20 refl ected s imilar patterns, The inductive effects o[ SP on HO- l and CCL20 wer e enhanced by HO- j inducer hemin and the membrane-permeable cGMP analog 8-bromo-cGMP, Conversely, this pathway was inJübited by t he 1-10난 inhi bitor zinc protoporphyrin IX(ZnPP IX) and the selective inl뼈itor of guanylate cyc1ase‘ lH-[l , 2, 4Joxad iazole[4‘ 3-aJquinoxal in-l-one (ODQ) , We report herein the pathway that connects SP along with other modulators 。f neuroimmunoregulationto the induction of HO-l and t he inflammatory mediator MIP-3a /CCL20 in IPDL cell s‘ which play an important role in the development 01' periodontitis or inflamrnation during orthodontic tooth movem