MMP-2 activation by Actinobacillus actinomycetemcomitans supernatant in human PDL cells was corresponded with reduction of TIMP-2

OBJECTIVE: Matrix metalloproteinase 2 (MMP-2) has been implicated to play a role in pathogenesis of periodontal disease. We recently reported that Porphyromonas gingivalis supernatant could activate MMP-2 in human periodontal ligament (HPDL) cells. In this study, activation of MMP-2 by Actinobacillus actinomycetemcomitans supernatant and the mechanism was investigated. METHODS: HPDL cells were treated with either A. actinomycetemcomitans or P. gingivalis supernatant for 48 h. To verify the mechanism, pretreated inhibitors were used. Gelatin zymography, RT-PCR and Western blot analysis were used to detect the activation of MMP-2, expression of MT1-MMP and TIMP-2 mRNA and the proteins, respectively. RESULTS: The supernatant from A. actinomycetemcomitans could activate MMP-2 in HPDL cells similar to that from P. gingivalis but by a different mechanism. Activation by A. actinomycetemcomitans supernatant was correlated with a reduction of TIMP-2 secretion without any alteration of MT1-MMP, while activation by P. gingivalis increased MT1-MMP but no change of TIMP-2 was found. CONCLUSION: The supernatant from A. actinomycetemcomitans and P. gingivalis could induce the activation of MMP-2 possibly through the imbalance of MT1-MMP and TIMP-2 in HPDL cells but by different mechanisms. The imbalance of MT1-MMP and TIMP-2 may be another factor that is involved in the severity of periodontal disease.     

Aberrant expression of Smad4, a TGF-beta signaling molecule, in oral squamous cell carcinoma

Although carcinogenesis of oral squamous cell carcinoma (OSCC) has been studied by many investigators in the past decade, the available evidence about its molecular mechanism is inconclusive. The objective of the present study was to compare expression of Smad4, a signaling molecule of the transforming growth factor beta (TGF-beta) pathway, between OSCC and normal oral mucosa. We assayed expression of Smad4 in OSCC and normal oral mucosa by performing immunohistochemistry using paraffin-embedded tissue samples. We also compared expression of Smad4 protein between OSCC lines and normal oral keratinocytes, using Western blot analysis. Smad4 expression was observed in only 60% of OSCC tissue samples, whereas it was observed in 82% of normal oral mucosa samples. Reduced Smad4 expression was clearly observed in all OSCC lines, compared with normal oral keratinocytes. These findings suggest that aberration of the TGF-beta pathway, as indicated by a reduction or absence of Smad4 expression, promotes carcinogenesis of OSCC.     

The validity of peer responses as a tool for screening at-risk students: a preliminary analysis

Students are becoming the majority of new amphetamine users in Thailand. This study compared urinalysis results with peer responses to individual characteristics related to substance use with the aim of identifying "at-risk" students. A randomly selected group of students from a public high school in northern Thailand was asked to fill out the names of classmates they viewed as having any of forty-three risk behaviors set out in a questionnaire. A total of 564 students were included, from whom urine specimens were collected on the first two days following the school break. An immunoassay test was used to screen the specimens and positive results were confirmed using thin-layer chromatography. About 4% of urinalysis results were methamphetamine-positive. Using urine test results as the standard, the sensitivity of peer responses to alienated behavior was 81.8%, while frequent class/school absenteeism and low concentration levels were somewhat lower, at 77% and 68%, respectively. Delinquency showed the least sensitivity at 50%. The McNemar chi2 test showed significant differences between urine test results and each peer response subscale (p < 0.001). This preliminary analysis has shown that peer responses with regard to substance-related behavior compare well with urine test results.     

The synergistic effect of TGF-beta and 1,25-dihydroxyvitamin D3 on SPARC synthesis and alkaline phosphatase activity in human pulp fibroblasts

1,25(OH)2D3 and TGF-beta can influence the function and differentiation of dental pulp fibroblasts. In this study, we examined the effect of 1,25(OH)2D3 and TGF-beta on the synthesis of SPARC and ALP activity in human pulp fibroblasts. Two isoforms of SPARC, the 43 and 38 kDa, were detected in this cell type. TGF-beta increased the synthesis of SPARC about 2.5-fold after 3 days of treatment but had no effect on the ALP activity. On the contrary, 1,25(OH)2D3 increased ALP activity 2-fold but had no effect on SPARC. The combination of TGF-beta and 1,25(OH)2D3 significantly induced SPARC synthesis and ALP activity by 5 and 9 folds, respectively (P<0.05). This finding suggested the synergistic effect between TGF-beta and 1,25(OH)2D3 in dental pulp fibroblasts on the synthesis of SPARC and ALP activity. This interaction could influence the function and differentiation of dental pulp fibroblasts.