Genetic variation in catechol-O-methyltransferase is associated with individual differences in conditioned pain modulation in healthy subjects.

BACKGROUND: Genetic variation in the catechol-O-methyltransferase (COMT) gene is associated with sensitivity to both acute experimental pain and chronic pain conditions. Four single nucleotide polymorphisms (SNPs) have traditionally been used to infer three common haplotypes designated as low, average and high pain sensitivity and are reported to affect both COMT enzymatic activity and pain sensitivity. One mechanism that may partly explain individual differences in sensitivity to pain is conditioned pain modulation (CPM). We hypothesized that variation in CPM may have a genetic basis. METHODS: We evaluated CPM in 77 healthy pain-free Caucasian subjects by applying repeated mechanical stimuli to the dominant forearm using 26-g von Frey filament as the test stimulus with immersion of the non-dominant hand in hot water as the conditioning stimulus. We assayed COMT SNP genotypes by the TaqMan method using DNA extracted from saliva. RESULTS: SNP rs4680 (val158 met) was not associated with individual differences in CPM. However, CPM was associated with COMT low pain sensitivity haplotypes under an additive model (p = 0.004) and the effect was independent of gender. CONCLUSIONS: We show that, although four SNPs are used to infer COMT haplotypes, the low pain sensitivity haplotype is determined by SNP rs6269 (located in the 5' regulatory region of COMT), suggesting that inherited variation in gene expression may underlie individual differences in pain modulation. Analysis of 13 global populations revealed that the COMT low pain sensitivity haplotype varies in frequency from 13% to 44% and showed that two SNPs are sufficient to distinguish all COMT haplotypes in most populations.

Elevated antibodies against Epstein-Barr virus among individuals predicted to carry nasopharyngeal carcinoma susceptibility variants.

Epstein-Barr virus (EBV) is an obligatory factor in the development of nasopharyngeal carcinoma (NPC), and anti-EBV IgA antibodies are elevated many years prior to the development of NPC. Nearly all adults are infected with EBV, but only a few develop cancer, suggesting that additional co-factors, including genetic susceptibility, must be required for the disease to manifest. Individuals were selected from the Taiwan Family Study, a cohort of 3389 individuals from NPC multiplex families. Primary analyses were conducted among 671 individuals from 69 pedigrees with the strongest family history of disease (>3 NPC-affected family members). The likelihood that a given family member carried a NPC susceptibility variant was estimated using Mendelian segregation rules, assuming a dominant mode of inheritance. We compared anti-EBV IgA antibody seropositivity between family members predicted to be carriers of NPC-linked genetic variants and those with a lower likelihood of carrying such variants. Obligate carriers of NPC susceptibility variants (100 % predicted probability of harbouring the genetic mutation) were nine-fold more likely to be anti-EBV IgA positive compared to family members predicted not to carry disease-causing variants (OR=9.2; P-trend<0.001). This elevated risk was confirmed in analyses restricted to both unaffected individuals and pedigrees with EBV-related pathway variants identified through exome sequencing. Our data indicate that family members who are more likely to carry NPC susceptibility variants are also more likely to be anti-EBNA1 IgA seropositive. Genetic susceptibility associated with control over this common herpes virus is likely a co-factor in determining which EBV-infected adults develop NPC.

Genetics of chronic post-surgical pain: a crucial step toward personal pain medicine.

PURPOSE: Most patients who undergo surgery or experience a traumatic injury suffer from acute pain that subsides once tissues heal. Nevertheless, the pain remains in 15-30% of patients, sometimes for life, and this chronic post-surgical pain (CPSP) can result in suffering, depression, anxiety, sleep disturbance, physical incapacitation, and an economic burden. The incorporation of genetic knowledge is expected to lead to the development of more effective means to prevent and manage CPSP using tools of personalized pain medicine. The purpose of this review article is to provide an update on the current state of CPSP genetics and its future potential. PRINCIPLE FINDINGS: The large variability in CPSP amongst patients undergoing similar surgery suggests that individual factors are significant contributors to CPSP, raising the possibility that CPSP is influenced by genetic determinants. Heritability estimates suggest that about half of the variance in CPSP levels is attributable to genetic variation. These estimates suggest that identifying the genetic underpinnings of CPSP may lead to significant improvements in treatment. Analyzing patients' DNA sequences, blood and salivary pain biomarkers, as well as their analgesic responses to medications will facilitate developing insights into CPSP pathophysiology and inform predictive algorithms to determine a patient's likelihood of developing CPSP even prior to surgery. These algorithms could facilitate effective treatment regimens that will protect against the transition to chronicity in traumatically injured patients or those scheduled for surgery and lead to better therapy for patients who have already developed CPSP. CONCLUSIONS: Pharmacogenomic technologies and strategies provide an opportunity to expand our knowledge in CPSP treatment that may manifest in a personalized approach to diagnosis, prevention, and therapy. Capitalizing on this genomic knowledge will necessitate the analysis of many tens of thousands of study patients. This will require an international coordinated effort to which anesthesiologists and surgeons can contribute substantially.

Inflammatory and oxidative stress responses of healthy young adults to changes in air quality during the Beijing Olympics.

RATIONALE: Unprecedented pollution control actions during the Beijing Olympics provided a quasi-experimental opportunity to examine biologic responses to drastic changes in air pollution levels. OBJECTIVES: To determine whether changes in levels of biomarkers reflecting pulmonary inflammation and pulmonary and systemic oxidative stress were associated with changes in air pollution levels in healthy young adults. METHODS: We measured fractional exhaled nitric oxide, a number of exhaled breath condensate markers (H(+), nitrite, nitrate, and 8-isoprostane), and urinary 8-hydroxy-2-deoxyguanosine in 125 participants twice in each of the pre- (high pollution), during- (low pollution), and post-Olympic (high pollution) periods. We measured concentrations of air pollutants near where the participants lived and worked. We used mixed-effects models to estimate changes in biomarker levels across the three periods and to examine whether changes in biomarker levels were associated with changes in pollutant concentrations, adjusting for meteorologic parameters. MEASUREMENTS AND MAIN RESULTS: From the pre- to the during-Olympic period, we observed significant and often large decreases (ranging from -4.5% to -72.5%) in levels of all the biomarkers. From the during-Olympic to the post-Olympic period, we observed significant and larger increases (48-360%) in levels of these same biomarkers. Moreover, increased pollutant concentrations were consistently associated with statistically significant increases in biomarker levels. CONCLUSIONS: These findings support the important role of oxidative stress and that of pulmonary inflammation in mediating air pollution health effects. The findings demonstrate the utility of novel and noninvasive biomarkers in the general population consisting largely of healthy individuals.

Follow-up study of veterans with white and red oral mucosal lesions at Veterans Affairs Dental Clinics.

OBJECTIVES: This analysis examined the clinical and histopathological characteristics of white and red oral mucosal lesions and patient lifestyle behaviors to understand how the lesions changed over 19-23 years, including among patients who developed oral and pharyngeal cancer. MATERIALS AND METHODS: Seventy-five individuals with red and/or white oral mucosal lesions with clinical diagnoses of smokeless tobacco lesions, leukoplakia, erythroplakia, lichen planus, ulcer, and virus-associated lesions were identified in six Veterans Affairs Medical Center Dental Clinics (VAMC) from 1996 to 2001. Biopsy results and patients' sociodemographic, medical, and tobacco/alcohol use characteristics were obtained. Study dentists used standardized forms to capture information about the lesions. Study participants were re-examined at intervals through January 2002. In 2020, a retrospective review of VAMC and public records ascertained whether participants developed oral cancer or died. RESULTS: The most common red or white oral mucosal lesions among the 75 study participants were leukoplakia (36.0%), smokeless tobacco lesions (26.7%), virus-associated lesions (18.7%), and lichen planus (16.0%). Lesions in 11% of participants with leukoplakia and one-third of participants with lichen planus persisted for 5 years or more. Dysplasia was present in four participants with leukoplakia. Seventeen percent of participants developed a new white or red oral mucosal lesion. Five patients (6.1%) developed oral or pharyngeal cancer, four among participants with leukoplakia (one with prior dysplasia) and one among participants with lichen planus. Four of the cancers developed 6-20 years after enrollment, and only one was at the original lesion site. CONCLUSIONS: The occurrence of oral and pharyngeal cancers in some study participants with white and red oral mucosal lesions many years after enrollment reinforces the need for patients, dentists, and health care systems to have better methods to identify and assess the malignant potential of oral lesions, monitor patients over time, and intercept high-risk oral lesions before they become cancerous.

Association between changes in air pollution levels during the Beijing Olympics and biomarkers of inflammation and thrombosis in healthy young adults.

CONTEXT: Air pollution is a risk factor for cardiovascular diseases (CVD), but the underlying biological mechanisms are not well understood. OBJECTIVE: To determine whether markers related to CVD pathophysiological pathways (biomarkers for systemic inflammation and thrombosis, heart rate, and blood pressure) are sensitive to changes in air pollution. DESIGN, SETTING, AND PARTICIPANTS: Using a quasi-experimental opportunity offered by greatly restricted air pollution emissions during the Beijing Olympics, we measured pollutants daily and the outcomes listed below in 125 healthy young adults before, during, and after the 2008 Olympics (June 2-October 30). We used linear mixed-effects models to estimate the improvement in outcome levels during the Olympics and the anticipated reversal of outcome levels after pollution controls ended to determine whether changes in outcome levels were associated with changes in pollutant concentrations. MAIN OUTCOME MEASURES: C-reactive protein (CRP), fibrinogen, von Willebrand factor, soluble CD40 ligand (sCD40L), soluble P-selectin (sCD62P) concentrations; white blood cell count (WBC); heart rate; and blood pressure. RESULTS: Concentrations of particulate and gaseous pollutants decreased substantially (-13% to -60%) from the pre-Olympic period to the during-Olympic period. Using 2-sided tests conducted at the .003 level, we observed statistically significant improvements in sCD62P levels by -34.0% (95% CI, -38.4% to -29.2%; P < .001) from a pre-Olympic mean of 6.29 ng/mL to a during-Olympic mean of 4.16 ng/mL and von Willebrand factor by -13.1% (95% CI, -18.6% to -7.5%; P < .001) from 106.4% to 92.6%. After adjustments for multiple comparisons, changes in the other outcomes were not statistically significant. In the post-Olympic period when pollutant concentrations increased, most outcomes approximated pre-Olympic levels, but only sCD62P and systolic blood pressure were significantly worsened from the during-Olympic period. The fraction of above-detection-limit values for CRP (percentage ≥ 0.3 mg/L) was reduced from 55% in the pre-Olympic period to 46% in the during-Olympic period and reduced further to 36% in the post-Olympic period. Interquartile range increases in pollutant concentrations were consistently associated with statistically significant increases in fibrinogen, von Willebrand factor, heart rate, sCD62P, and sCD40L concentrations. CONCLUSIONS: Changes in air pollution levels during the Beijing Olympics were associated with acute changes in biomarkers of inflammation and thrombosis and measures of cardiovascular physiology in healthy young persons. These findings are of uncertain clinical significance.

Familial tendency and risk of nasopharyngeal carcinoma in taiwan: effects of covariates on risk.

In the present study, the authors compared the long-term risk of nasopharyngeal carcinoma (NPC) of male participants in an NPC multiplex family cohort with that of controls in a community cohort in Taiwan after adjustment for anti-Epstein-Barr virus (EBV) seromarkers and cigarette smoking. A total of 43 incident NPC cases were identified from the 1,019 males in the NPC multiplex family cohort and the 9,622 males in the community cohort, for a total of 8,061 person-years and 185,587 person-years, respectively. The adjusted hazard ratio was 6.8 (95% confidence interval (CI): 2.3, 20.1) for the multiplex family cohort compared with the community cohort. In the evaluation of anti-EBV viral capsid antigen immunoglobulin A and anti-EBV deoxyribonuclease, the adjusted hazard ratios were 2.8 (95% CI: 1.3, 6.0) and 15.1 (95% CI: 4.2, 54.1) for those positive for 1 EBV seromarker and positive for both seromarkers, respectively, compared with those negative for both EBV seromarkers. The adjusted hazard ratio was 31.0 (95% CI: 9.7, 98.7) for participants who reported a family history of NPC and who were anti-EBV-seropositive compared with individuals without such a history who were anti-EBV-seronegative. The findings suggest that both family history of NPC and anti-EBV seropositivity are important determinants of subsequent NPC risk and that the effect of family history on NPC risk cannot be fully explained by mediation through EBV serologic responses.

Cancer patterns in nasopharyngeal carcinoma multiplex families in Taiwan.

Genetic and environmental factors have been implicated in the etiology of nasopharyngeal carcinoma (NPC), a tumor known to be closely associated with Epstein-Barr virus (EBV) infection. Studies have reported familial aggregation of NPC and have suggested the possible aggregation of NPC and other cancers. We evaluated familial aggregation of cancer in 358 high-risk families with two or more NPC cases enrolled in a NPC genetics study in Taiwan. Participants were linked to the Taiwan National Cancer Registry to identify incident cancers diagnosed after study enrollment (started in 1996) and before December 31, 2005, or death. In total, 2,870 individuals from the NPC Multiplex Family Study contributed 15,151 person-years over an average of 5.3 years of follow-up. One hundred ten incident cancers were identified. Multiple-primary standardized incidence ratios (MP-SIRs) were computed to evaluate overall cancer risk associated with infectious agents and with other tumors. The overall MP-SIR was 1.3 (95% CI: 1.1-1.6), which was largely explained by an excess in NPC (MP-SIR = 15; 95% CI: 10-23). Exclusion of incident NPC diagnoses led to an overall MP-SIR of 1.0 (95% CI: 0.83-1.3). Similarly, the observed excess risk of cancers associated with infectious agents (MP-SIR = 2.0; 95% CI: 1.5-2.6) was driven by the excess in NPC; exclusion of NPC cases led to a reduced MP-SIR that did not differ from 1.0. Analysis of the largest NPC multiplex family study to date confirms the presence of coaggregation of NPC within families in Taiwan but does not provide evidence for a broader familial syndrome involving NPC and other tumors.

Unique etiologic, demographic, and pathologic characteristics of localized aggressive periodontitis support classification as a distinct subcategory of periodontitis.

BACKGROUND: Localized aggressive periodontitis (LAgP) occurs in 2% of African-American adolescents but only 0.15% of white adolescents. First molars and incisors are affected by rapid onset and progression. METHODS: This nonsystematic critical review evaluated published data for LAgP and chronic periodontitis (CP), focusing on potential differences in epidemiology, microbiology, immunology, genetics, and response to therapy. RESULTS: LAgP differs from CP by localization to incisors and first molars, early onset and rapid progression in adolescents and young adults, and a 10-fold higher prevalence in populations of African or Middle Eastern origin, often with strong familial aggregation. The bacterium Aggregatibacter actinomycetemcomitans and hyperresponsive neutrophils are frequently observed. Antibiotic and nonsurgical therapies are highly effective. CONCLUSIONS: LAgP differs in many ways from the far more common CP that affects older adults. The substantial evidence of dissimilarities summarized in this review strongly supports the classification of LAgP as a distinct form of periodontitis. PRACTICAL IMPLICATIONS: Classifying LAgP as a distinct subcategory of periodontitis will encourage future research and does not conflict with the newly proposed "staging and grading" system. The silent onset and rapid progression of LAgP make early diagnosis and frequent follow-up with patients essential for effective treatment.

Whole-Exome Sequencing of Nasopharyngeal Carcinoma Families Reveals Novel Variants Potentially Involved in Nasopharyngeal Carcinoma.

Genetic susceptibility is likely involved in nasopharyngeal carcinoma (NPC), a cancer caused by Epstein-Barr virus (EBV) infection. Understanding of genetic factors involved in NPC and how they contribute to EBV-induced carcinogenesis is limited. We conducted whole-exome capture/sequencing among 251 individuals from 97 multiplex families from Taiwan (205 affected, 21 obligate carriers, and 25 unaffected) using SeqCap EZ Human Exome Library v3.0 and Illumina HiSeq. Aligned sequences were filtered to identify likely-to-be-functional deleterious variants that co-segregated with disease. Ingenuity Pathway analysis was performed. Circulating magnesium levels were measured in 13 individuals in 2 families with NIPAL1 mutations and in 197 sporadic NPC cases and 237 controls. We identified variants in 12 genes likely involved in cancer pathogenesis, viral infection or immune responses to infection. These included genes postulated to be involved in magnesium transport (NIPAL1), EBV cell entry (ITGB6), modulation of EBV infection (BCL2L12, NEDD4L), telomere biology (CLPTM1L, BRD2, HNRNPU), modulation of cAMP signaling (RAPGEF3), DNA repair (PRKDC, MLH1), and Notch signaling (NOTCH1, DLL3). Pathway based analysis demonstrated enrichment for Notch signaling genes (p-value = 0.0006). Evaluation of individuals within NIPAL1 families suggested lower serum magnesium in NPC compared to unaffected members. A significant reduction in serum magnesium levels was observed among sporadic NPC cases compared to controls (7.1% NPC/1.7% controls below normal range; OR = 4.5; 95% CI = 1.4,14) and is consistent with findings demonstrating a role for magnesium channeling in T-cell responses to EBV. We identified novel genes associated with NPC that point to new areas of inquiry to better understand genetic factors that determine the fate of viral infections and/or otherwise predisposes to NPC.

Mouse model demonstrates strain differences in susceptibility to opioid side effects.

Individual differences have been observed in responses to opioid drugs, including common side effects. In this study, the inbred mouse strains A/J and C57BL/6J were used to determine whether their specific strain differences correlate with differences in susceptibility to respiratory depression and constipation. To measure the effects of morphine on respiration, morphine at 15 and 40 mg/kg was injected subcutaneously. Respiratory parameters were then measured 30 and 60 min later. To measure the effects on constipation, 5, 15, 40, and 60 mg/kg doses were administered subcutaneously three times daily for three days. Gastrointestinal transit distance was then measured using the charcoal bolus test. C57BL/6J mice showed a greater degree of change in several respiratory parameters, resulting in more pronounced respiratory depression. C57BL6J mice also showed significantly more constipation than A/J mice with 40 and 60 mg/kg morphine doses. This study demonstrates that the strain differences between A/J and C57BL/6J mice have a major effect on opioid-induced constipation and respiratory depression. These correlations are of great clinical interest, as they could lead to the development of methods for reducing side effects.

Self-awareness of premalignant oral lesions among veterans attending six U.S. Veterans Affairs Medical Centers.

Early identification is key to reducing the morbidity and mortality of oropharyngeal cancer. This study identified factors associated with self-awareness among patients newly diagnosed with a premalignant oral lesion. Data describing sociodemographics, medical/dental histories, tobacco/alcohol use and oral health were obtained by questionnaire and clinical examination of 73 veterans at six U.S. Veterans Affairs Medical Centers. Lesion types included homogenous and non-homogenous leukoplakia, smokeless tobacco lesion (STL), papilloma, lichen planus and erythroplakia. Prior to diagnosis, 29 subjects (39.7%) were unaware of their lesion. In bivariate analyses, lesion self-awareness was associated with anatomic location, multifocal/generalized appearance, pain, oral sores, and cigar use (p<0.05). Awareness varied with lesion diagnosis and was more likely with STL and less likely with homogenous leukoplakia (p<0.05). In multivariate analyses, awareness was predicted by the presence of a lesion on easily visible mucosa (adjusted odds ratio, OR=11.2) and a history of mouth sores (OR= 11.2). These findings identified marked variations in patient self-awareness of oral premalignant conditions.

Insulin-like growth factor II receptor gene-167 genotype increases the risk of oral squamous cell carcinoma in humans.

Our purpose was to evaluate inherited short tandem repeat polymorphisms of the insulin-like growth factor II receptor gene (IGF2R) in oral cancer risk. The 197 individuals that consented to participate in a hospital-based, case-control study were interviewed with a structured questionnaire and provided blood and saliva. DNA was extracted for genotyping using a PCR-based method. Odds ratios were calculated using multivariate logistic regression. Subjects carrying the heterozygous 167-bp IGF2R genotype had a 2.7-fold higher risk of oral cancer compared with subjects with other genotypes (odds ratio = 2.7, 95% confidence interval: 1.16-6.48), controlling for major confounders. Our results suggest that genetic variation of IGF2R may influence significantly the risk of oral cancer.

Correlation of susceptibility to 6-aminonicotinamide and hydrocortisone-induced cleft palate.

Our previous genome-wide Quantitative Trait Locus (QTL) mapping study using mouse A/J by C57BL/6J recombinant inbred (RI) lines suggested several chromosomal regions contain genes influencing susceptibility to phenytoin (PT)-induced cleft lip with or without cleft palate [CL(P)] and 6-aminonicotinamide (6-AN)-induced isolated cleft palate (CP). Importantly, the same chromosomal regions but different RI parental strain alleles were sometimes implicated in susceptibility to these different kinds of orofacial clefting. Here we report the susceptibility to hydrocortisone (HC)-induced CP in these RI lines. We treated pregnant females with HC and studied the incidence of CP in day 17 fetuses. RI lines showed highly correlated responses to HC and 6-AN. The A/J parental line and five RI lines showed very high levels of clefting in response to both of these teratogens. The C57BL/6J parental line and five other RI lines exhibited low incidence of CP for these teratogens. In contrast, there was no significant correlation between incidence of PT-induced CL(P) and HC-induced CP.

Quantitative measures of aggressive periodontitis show substantial heritability and consistency with traditional diagnoses.

BACKGROUND: Aggressive periodontitis (AgP) research nearly always classifies subjects into traditional discrete categories of localized or generalized, based upon degree of attachment loss (AL) and types of affected teeth. Since AL is continuous and quantitative, however, useful information is lost. We developed quantitative measures of AgP, compared these to traditional methods, and estimated heritabilities in families. METHODS: We examined 237 healthy, 169 localized AgP, and 204 generalized AgP subjects. We used the site of maximum AL of each tooth to calculate means for each subject for different groups of teeth. We also applied principal components analysis (PCA) to condense variation among 28 teeth into three orthogonal (uncorrelated) variables. We used discriminant function analysis (DFA) to evaluate how well the quantitative measures match with traditional classifications. Quantitative trait heritabilities were estimated by variance components. RESULTS: PCA clustered first molars, incisors, and the other teeth into three groups. DFA showed that quantitative measures classified subjects consistent with traditional methods (87% to 94% agreement). Heritabilities ranged from 13.7% (P = 0.10) to 30.0% (P = 0.008) for quantitative measures, with highest values obtained for first molars. A combination of the principal component variables most heavily weighted on first molars and incisors gave the best model of disease susceptibility, with good separation of healthy versus diseased subjects, independent of disease extent or severity. CONCLUSIONS: Quantitative measures may provide improved precision and power for many kinds of periodontal research. Our finding of significant heritability supports their use in gene mapping studies of AgP susceptibility.

Interleukin 1 genetic tests provide no support for reduction of preventive dental care.

BACKGROUND: It has been proposed that the PST and PerioPredict genetic tests that are based on polymorphisms in interleukin 1 (IL-1) genes identify a subset of patients who experience fewer tooth extractions if provided with 2 annual preventive visits. Economic analyses indicate rationing preventive care to only "high-risk" genotypes, smokers, patients with diabetes, or combinations of these risk factors would reduce the cost of dental care by $4.8 billion annually in the United States. METHODS: Data presented in the study that claimed clinical utility for the PST and PerioPredict tests were obtained for reanalysis using logistic regression to assess whether the PST genetic test, smoking, diabetes, or number of preventive visits were risk factors for tooth extraction during a span of 16 years. Consistency of risk classification by the PST (version 1) and PerioPredict (version 2) genetic tests was evaluated in different ethnic groups from the 1000 Genomes database. RESULTS: Multivariate analyses revealed association of tooth extraction with diabetes (P < .0001), smoking (P < .0001), and number of preventive visits (P = .004), but no support for the PST genetic test (P = .96) nor indication that the benefit of 2 preventive visits was affected by this genetic test (P = .58). Classification of risk was highly inconsistent between the PST (version 1) and PerioPredict (version 2) genetic tests. CONCLUSIONS: Two annual preventive visits were supported as beneficial for all patients, and there was no evidence that the IL-1 PST genetic test has any effect on tooth extraction risk or influences the benefits of 2 annual preventive visits. PRACTICAL IMPLICATIONS: Neither IL-1 PST nor PerioPredict genetic tests are useful for rationing preventive dental care. Further research is needed to identify genetic biomarkers with robust clinical validity and clinical utility to effectively personalize the practice of dentistry.

Altered pain modulation in patients with persistent postendodontic pain.

Persistent pain may follow nerve injuries associated with invasive therapeutic interventions. About 3% to 7% of the patients remain with chronic pain after endodontic treatment, and these are described as suffering from painful posttraumatic trigeminal neuropathy (PTTN). Unfortunately, we are unable to identify which patients undergoing such procedures are at increased risk of developing PTTN. Recent findings suggest that impaired endogenous analgesia may be associated with the development of postsurgical chronic pain. We hypothesized that patients with PTTN display pronociceptive pain modulation, in line with other chronic pain disorders. Dynamic (conditioned pain modulation, temporal summation) and static (response to mechanical and cold stimulation) psychophysical tests were performed intraorally and in the forearm of 27 patients with PTTN and 27 sex- and age-matched controls. The dynamic sensory testing demonstrated less efficient conditioned pain modulation, suggesting reduced function of the inhibitory endogenous pain-modulatory system, in patients with PTTN, mainly in those suffering from the condition for more than a year. The static sensory testing of patients with PTTN demonstrated forearm hyperalgesia to mechanical stimulation mainly in patients suffering from the condition for less than a year and prolonged painful sensation after intraoral cold stimulus mainly in patients suffering from the condition for more than a year. These findings suggest that PTTN is associated more with the inhibitory rather than the facilitatory arm of pain modulation and that the central nervous system has a role in PTTN pathophysiology, possibly in a time-dependent fashion.

Mapping a gene for neuropathic pain-related behavior following peripheral neurectomy in the mouse.

Total hindpaw denervation in rodents elicits an abnormal behavior of licking, scratching and self-injury of the anesthetic limb ("autotomy"). Since the same denervation produces phantom limb pain and anesthesia dolorosa in humans, autotomy has been used as a model of human neuropathic pain. Autotomy is an inherited trait in rodents, attributable to a few genes of major effect. Here we used recombinant inbred (RI) mouse lines of the AXB-BXA RI set to map a gene for autotomy. Autotomy levels following unilateral sciatic and saphenous nerve section were scored daily for 36 days, using a standardized scale, in all 23 RI lines available for this set. We used a genetic map of 395 marker loci and a permutation-based statistical method for categorical data to assess the statistical significance of mapping results. We identified a marker on chromosome 15 with statistical support (P=0.0003) in the range considered significant for genome-wide scans in the mouse. Several genes located in this chromosomal region encode for neural functions related to neuropathic pain and may indicate targets for development of novel analgesics.

Metabolic polymorphisms, smoking, and oral cancer in Puerto Rico.

Genetic polymorphisms resulting in variation in metabolism of tobacco carcinogens may influence oral cancer risk. In a population-based case-control study in Puerto Rico, genotypes of CYP1A1, GSTM1, and GSTT1 were determined by a PCR-based method for 132 oral cancer patients and 143 control subjects. Genotype-associated risks were estimated by logistic regression. The null variant of GSTM1 was associated with a marginally significant decrease in oral cancer risk [odds ratio (OR) = 0.6, 95% confidence interval (CI) = 0.3-1.0, and P for trend = 0.09]. Risks increased with increasing cigarette use among subjects with the GSTM1-present genotype (P for trend <0.0001), rising to OR = 9.5, 95% CI = 3.0-30, among the heaviest cigarette users. In contrast, among subjects with the GSTM1-null genotype, risks did not clearly increase with increasing cigarette use (P for trend <0.61; OR = 1.8, 95% CI = 0.6-5.2 among the heaviest tobacco users). The GSTT1-null variant (OR = 1.0, 95% CI = 0.5-1.9) and CYP1A1(462Val) variant (OR = 0.9, 95% CI = 0.5-1.7) were not associated with the risk. Risks rose with increasing cigarette use in a similar manner for subjects with or without the CYP1A1(462Val) variant (P for interaction = 0.3) and for subjects with or without the GSTT1-null genotype (P for interaction = 0.4). In conclusion, cigarette use significantly increased the risk of oral cancer in this population. The GSTM1-present genotype was associated with higher tobacco-associated risk for oral cancer among heavy smokers than the null genotype.