Kanokporn Bhalang

Catechol-O-methyltransferase gene polymorphisms are associated with multiple pain-evoking stimuli

&NA; Variations in the gene encoding catechol‐O‐methyltransferase (COMT) are linked to individual differences in pain sensitivity. A single nucleotide polymorphism (SNP) in codon 158 (val158met), which affects COMT protein stability, has been associated with the human experience of pain. We recently demonstrated that three common COMT haplotypes, which affect the efficiency of COMT translation, are strongly associated with a global measure of pain sensitivity derived from individuals’ responses to noxious thermal, ischemic, and pressure stimuli. Specific haplotypes were associated with low (LPS), average (APS), or high (HPS) pain sensitivity. Although these haplotypes included the val158met SNP, a significant association with val158met variants was not observed. In the present study, we examined the association between COMT genotype and specific pain‐evoking stimuli. Threshold and tolerance to thermal, ischemic, and mechanical stimuli, as well as temporal summation to heat pain, were determined. LPS/LPS homozygotes had the least, APS/APS homozygotes had average, and APS/HPS heterozygotes had the greatest pain responsiveness. Associations were strongest for measures of thermal pain. However, the rate of temporal summation of heat pain did not differ between haplotype combinations. In contrast, the val158met genotype was associated with the rate of temporal summation of heat pain, but not with the other pain measures. This suggests that the val158met SNP plays a primary role in variation in temporal summation of pain, but that other SNPs of the COMT haplotype exert a greater influence on resting nociceptive sensitivity. Here, we propose a mechanism whereby these two genetic polymorphisms differentially affect pain perception.

Influence of Psychological Factors on Risk of Temporomandibular Disorders

Psychological characteristics potentially may be a cause or consequence of temporomandibular disorder (TMD). We hypothesized that psychological characteristics associated with pain sensitivity would influence risk of first-onset TMD, but the effect could be attributed to variation in the gene encoding catechol-O-methyltransferase (COMT). We undertook a prospective cohort study of healthy female volunteers aged 18–34 yrs. At baseline, participants were genotyped, they completed psychological questionnaires, and underwent quantitative sensory testing to determine pain sensitivity. We followed 171 participants for up to three years, and 8.8% of them were diagnosed with first-onset TMD. Depression, perceived stress, and mood were associated with pain sensitivity and were predictive of 2- to 3-fold increases in risk of TMD (P < 0.05). However, the magnitude of increased TMD risk due to psychological factors remained unchanged after adjustment for the COMT haplotype. Psychological factors linked to pain sensitivity influenced TMD risk independently of the effects of the COMT haplotype on TMD risk.

Development of Temporomandibular Disorders is associated with greater bodily pain experience

ObjectivesThe aim of this study is to examine the difference in the report of bodily pain experienced by patients who develop temporomandibular disorders (TMD) and by those who do not develop TMD over a 3-year observation period. MethodsThis is a 3-year prospective study of 266 females aged 18 to 34 years initially free of TMD pain. All patients completed the Symptom Report Questionnaire (SRQ) at baseline and yearly intervals, and at the time they developed TMD (if applicable). The SRQ is a self-report instrument evaluating the extent and location of pain experienced in the earlier 6 months. Statistical analysis was carried out using repeated measures ANOVA. ResultsOver the 3-year period, 16 patients developed TMD based on the Research Diagnostic Criteria for TMD. Participants who developed TMD reported more headaches (P=0.0089), muscle soreness or pain (P=0.005), joint soreness or pain (P=0.0012), back pain (P=0.0001), chest pain (P=0.0004), abdominal pain (P=0.0021), and menstrual pain (P=0.0036) than Participants who did not develop TMD at both the baseline and final visits. Participants who developed TMD also reported significantly more headache (P=0.0006), muscle soreness or pain (P=0.0059), and other pains (P=0.0188) when they were diagnosed with TMD compared with the baseline visit. DiscussionThe development of TMD was accompanied by increases in headaches, muscle soreness or pain, and other pains that were not observed in the Participants who did not develop TMD. Participants who developed TMD also report higher experience of joint, back, chest, and menstrual pain at baseline.

The application of acetic acid in the detection of oral squamous cell carcinoma.

BACKGROUND Oral cancer is the fourth most common cancer in males and the seventh most common cancer in females in Thailand. The survival rates and quality of life of oral cancer patients will significantly be improved if they receive treatment for lesions that are less advanced or premalignant. Early diagnosis is therefore of paramount importance. A number of techniques have been developed to supplement clinical examination for oral malignancy. One interesting screening method is the application of 3% to 5% acetic acid, which has been used for cervical cancer screening. OBJECTIVES The primary objective of this study was to assess the sensitivity, specificity, and accuracy of using vinegar (5% acetic acid) for the examination of oral cancer. The secondary objective was to investigate the association between clinical examination using acetic acid and expression of the tumor marker, p53. METHODS The study included 30 participants suspected of having oral squamous cell carcinoma. Five percent acetic acid was applied to the lesions, followed by incisional biopsy. The specimens were microscopically examined for pathological diagnosis and p53 immunohistochemical investigation. RESULTS The sensitivity, specificity, and accuracy of using acetic acid for oral cancer examination were 83.33%, 84.21%, and 83.64%, respectively. There was a statistically significant association between clinical examination using acetic acid and expression of p53 protein (P = .000). CONCLUSIONS The results of this study suggest that 5% acetic acid has high sensitivity, specificity, and accuracy in detecting oral squamous cell carcinoma and might be used as an adjunct for oral cancer examination.

Intermittent Compressive Stress Enhanced Insulin-Like Growth Factor-1 Expression in Human Periodontal Ligament Cells

Mechanical force was shown to promote IGF-1 expression in periodontal ligament both in vitro and in vivo. Though the mechanism of this effect has not yet been proved, here we investigated the molecular mechanism of intermittent mechanical stress on IGF-1 expression. In addition, the role of hypoxia on the intermittent compressive stress on IGF-1 expression was also examined. In this study, human periodontal ligament cells (HPDLs) were stimulated with intermittent mechanical stress for 24 hours. IGF-1 expression was examined by real-time polymerase chain reaction. Chemical inhibitors were used to determine molecular mechanisms of these effects. For hypoxic mimic condition, the CoCl2 supplementation was employed. The results showed that intermittent mechanical stress dramatically increased IGF-1 expression at 24 h. The pretreatment with TGF-β receptor I or TGF-β1 antibody could inhibit the intermittent mechanical stress-induced IGF-1 expression. Moreover, the upregulation of TGF-β1 proteins was detected in intermittent mechanical stress treated group. Correspondingly, the IGF-1 expression was upregulated upon being treated with recombinant human TGF-β1. Further, the hypoxic mimic condition attenuated the intermittent mechanical stress and rhTGF-β1-induced IGF-1 expression. In summary, this study suggests intermittent mechanical stress-induced IGF-1 expression in HPDLs through TGF-β1 and this phenomenon could be inhibited in hypoxic mimic condition.