Abstract. Several epidemiological studies have reported that temporomandibular disorder is more prevalent in women, which suggests the involvement of sex hormones, such as estrogen, in the pathogenesis of this disease. PCR amplification and Western blotting were employed to target the expression of estrogen receptors (ERs) in human fibroblast-like synovial and ATDC5 cells. The effect of estrogen was investigated through the expression of RANKL, osteoprotegerin (OPG), M-CSF/CSF-1 and c-fms. We showed expression of M-CSF/ CSF-1 and c-fms, with time-dependent increase in both after the addition of estrogen. Based on previous studies reporting that M-CSF/CSF-1 regulates the proliferation and differentiation of hemopoietic progenitor cells into mature macrophages, we put forward a new hypothesis based on the increased inflammation and tendency of females to suffer more from temporomandibular disorder (TMD) in the presence of external exacerbating factors. Detection of RANKL and OPG in ATDC5 and expression of both in HFLS was confirmed with complete disappearance of the RANKL band, and marked increase in the expression of OPG after 1 h from the addition of estrogen.

Temporomandibular disorder (TMD), a progressive disease entity, and osteoarthrosis preferentially affect females, denoting a possible role of estrogen. Using RAW 264.7 cells, the expression of estrogen receptors (ERs) α and ß and the consequent effect of estrogen was investigated. We present the novel detection of ER ß expression in RAW 264.7 cells. Furthermore, we innovatively demonstrated the increase in expression of both ER α and ß, as well as RANK and c-fms, with estrogen treatment. However, a decrease in expression of c-fms, RANK and ER ß, and nearly no change in the expression of ER α were experienced upon further increase in estrogen concentrations. These findings lead us to hypothesize a new mechanism of inflammation in TMD.

Modulation of the physiologically influential Na(+),K(+)-ATPase is a complex process involving a wide variety of factors. To determine the possible effects of the protein tyrosine phosphatase (PTP) inhibitors dephostatin and Et-3,4-dephostatin on human and pig, renal cells and enzymatic extracts, we treated our samples (15 min-24 h) with those PTP inhibitors (0-100 microM). PTP inhibitors were found to possess a concentration-dependent inhibition of Na(+),K(+)-ATPase activity in both human and pig samples. The inhibition was similarly demonstrated on all cellular, microsomal fraction and purified Na(+),K(+)-ATPase levels. Despite rigorous activity recovery attempts, the PTP inhibitors' effects were sustained on Na(+),K(+)-ATPase activity. Western blotting experiments revealed the expression of both alpha(1)- and beta(1)-subunits in both human and pig tissues. alpha(1)-Subunits possessed higher tyrosine phosphorylation levels with higher concentrations of PTP inhibitors. Meanwhile, serine/threonine residues of both alpha(1)- and beta(1)-subunits demonstrated diminished phosphorylation levels upon dephostatin treatment. Accordingly, we provide evidence that Na(+),K(+)-ATPase can be regulated through tyrosine phosphorylation of primarily their alpha(1)-subunits, using PTP inhibitors.

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