Assessing potentiation of the (α4)3(β2)2 nicotinic acetylcholine receptor by the allosteric agonist CMPI

The extracellular domain of the nicotinic acetylcholine receptor isoforms formed by three α4 and two β2 subunits ((α4)3(β2)2 nAChR) harbors two high-affinity “canonical” acetylcholine (ACh)-binding sites located in the two α4:β2 intersubunit interfaces and a low-affinity “noncanonical” ACh-binding site located in the α4:α4 intersubunit interface. In this study, we used ACh, cytisine, and nicotine (which bind at both the α4:α4 and α4:β2 interfaces), TC-2559 (which binds at the α4:β2 but not at the α4:α4 interface), and 3-(2-chlorophenyl)-5-(5-methyl-1-(piperidin-4-yl)-1H-pyrrazol-4-yl)isoxazole (CMPI, which binds at the α4:α4 but not at the α4:β2 interface), to investigate the binding and gating properties of CMPI at the α4:α4 interface. We recorded whole-cell currents from Xenopus laevis oocytes expressing (α4)3(β2)2 nAChR in response to applications of these ligands, alone or in combination. The electrophysiological data were analyzed in the framework of a modified Monod–Wyman–Changeux allosteric activation model. We show that CMPI is a high-affinity, high-efficacy agonist at the α4:α4 binding site and that its weak direct activating effect is accounted for by its inability to productively interact with the α4:β2 sites. The data presented here enhance our understanding of the functional contributions of ligand binding at the α4:α4 subunit interface to (α4)3(β2)2 nAChR-channel gating. These findings support the potential use of α4:α4 specific ligands to increase the efficacy of the neurotransmitter ACh in conditions associated with decline in nAChRs activity in the brain.

Examining the Effects of (α4)3(β2)2 Nicotinic Acetylcholine Receptor-Selective Positive Allosteric Modulator on Acute Thermal Nociception in Rats

Neuronal nicotinic acetylcholine receptor (nAChR)-based therapeutics are sought as a potential alternative strategy to opioids for pain management. In this study, we examine the antinociceptive effects of 3-(2-chlorophenyl)-5-(5-methyl-1-(piperidin-4-yl)-1H-pyrazol-4-yl)isoxazole (CMPI), a novel positive allosteric modulator (PAM), with preferential selectivity to the low agonist sensitivity (α4)3(β2)2 nAChR and desformylflustrabromine (dFBr), a PAM for α4-containing nAChRs. We used hot plate and tail flick tests to measure the effect of dFBr and CMPI on the latency to acute thermal nociceptive responses in rats. Intraperitoneal injection of dFBr, but not CMPI, dose-dependently increased latency in the hot plate test. In the tail flick test, the effect achieved at the highest dFBr or CMPI dose tested was only <20% of the maximum possible effects reported for nicotine and other nicotinic agonists. Moreover, the coadministration of dFBr did not enhance the antinociceptive effect of a low dose of nicotine. Our results show that the direct acute effect of dFBr is superior to that for CMPI, indicating that selectivity to (α4)3(β2)2 nAChR is not advantageous in alleviating responses to acute thermal nociceptive stimulus. However, further studies are necessary to test the suitability of (α4)3(β2)2 nAChR-selective PAMs in chronic pain models.

Long-term recreational physical activity and breast cancer in the National Health and Nutrition Examination Survey I epidemiologic follow-up study

Our purpose was to study the association between long-term recreational physical activity and breast cancer in the Epidemiological Follow-up Study (NHEFS) of the first National Health and Nutrition Examination Survey (NHANES I, 1971-1975). The analytic cohort included 6160 women who were free of breast cancer at the first NHEFS follow-up in 1982-1984 and had interview data on recreational physical activity (low, moderate, and high) in 1982-1984 and 10 years earlier, in 1971-1975. We created categories of long-term (1982-1984 + 1971-1975) recreational physical activity: (a) consistently low; (b) moderate/inconsistent; and (c) consistently high. Data were analyzed using Cox proportional hazard regression models. A total of 138 women developed breast cancer between 1982-1984 and 1992. In women > or =50 years of age in 1982-1984, consistently high (versus consistently low) recreational physical activity was associated with a 67% reduction in breast cancer risk (n = 96 cases; relative risk, 0.33; 95% confidence interval, 0.14-0.82; P for trend = 0.03); in women <50 years of age (n = 42 cases), there was no association. Associations were not modified by body mass index or by weight gain as an adult. High recreational physical activity over the long-term may reduce breast cancer risk in women > or =50 years of age; in this sample, it did so regardless of weight history.

Radiographic and clinical responses to periodontal therapy

Mechanical periodontal therapy is widely used for a variety of periodontal conditions. While the clinical efficacy of this treatment has been validated, the radiographic response has not been studied in depth. The purpose of the present study was to examine the clinical and radiographic response to mechanical periodontal therapy, and assess the factors associated with these changes. One hundred and eight patients, with established periodontitis, received oral hygiene instruction and mechanical periodontal therapy for a period of 4 to 5 weeks. Scheduled maintenance visits were performed at 3, 6, 9, and 15 months. Probing depth (PD) and attachment level (AL) measurements were performed at baseline, and at 3 and 15 months. Intraoral radiographs were taken at baseline and 12 to 15 months postsurgery using a Rinn alignment system. Alveolar crestal height (ACH) measurements were performed on a pair of digitized images of the previously taken radiographs. An overall mean of patients' changes for PD, AL, and ACH was initially computed. Active sites (gainers and losers) were determined using a threshold method, and expressed as patient's percentage of active sites (number of active sites of the total sites measured in each patient). Mean overall probing reduction and AL gain was 0.5 mm and 0.44 mm, respectively. Of all sites measured, 16.6% exhibited AL gain, while only 6.2% of all sites exhibited AL loss. Mean overall change in ACH was -0.07 mm, of which 11.8% of all sites exhibited ACH gain, while 15.1% exhibited loss beyond the threshold. Non-smokers presented no change in bone loss, while smokers continued to lose bone at an annual rate of 0.17 mm, despite treatment (P <0.005). Likewise, the average percent of sites per patients showing attachment gain beyond the threshold were much greater in non-smokers (13.9%) compared to 9.0% in smokers (P <0.01). Mean probing reduction was 50% greater among non-smokers (0.6 mm) when compared to smokers (0.4 mm), which was also statistically significant (P <0.05). A positive and significant correlation was established between the percentage of sites with AL gain and sites with ACH gain (Rho =0.40; P=0.0001). It is suggested that monitoring sites for AL and ACH gain expressed as changes beyond a selective threshold is an important outcome variable in treatment studies.