Objective Human and animal studies have shown that Nav1.7 sodium channels, which are preferentially expressed within nociceptors and sympathetic neurons, play a major role in inflammatory and neuropathic pain. Inherited erythromelalgia (IEM) has been linked to gain-of-function mutations of Nav1.7. We now report a novel mutation (V400M) in a three-generation Canadian family in which pain is relieved by carbamazepine (CBZ). Methods We extracted genomic DNA from blood samples of eight members of the family, and the sequence of SCN9A coding exons was compared with the reference Nav1.7 complementary DNA. Wild-type Nav1.7 and V400M cell lines were then analyzed using whole-cell patch-clamp recording for changes in activation, deactivation, steady-state inactivation, and ramp currents. Results Whole-cell patch-clamp studies of V400M demonstrate changes in activation, deactivation, steady-state inactivation, and ramp currents that can produce dorsal root ganglia neuron hyperexcitability that underlies pain in these patients. We show that CBZ, at concentrations in the human therapeutic range, normalizes the voltage dependence of activation and inactivation of this inherited erythromelalgia mutation in Nav1.7 but does not affect these parameters in wild-type Nav1.7. Interpretation Our results demonstrate a normalizing effect of CBZ on mutant Nav1.7 channels in this kindred with CBZ-responsive inherited erythromelalgia. The selective effect of CBZ on the mutant Nav1.7 channel appears to explain the ameliorative response to treatment in this kindred. Our results suggest that functional expression and pharmacological studies may provide mechanistic insights into hereditary painful disorders.

Background Pruritus can be a distressing and even debilitating symptom for patients with cutaneous T-cell lymphoma (CTCL). To date, few studies have evaluated the pathophysiology of this symptom. Due to this, therapy for pruritus in CTCL has mainly relied on those therapies that target and treat the lymphoma. For patients living with CTCL that relapses or becomes refractory to treatment, and who continue to experience severe itch, this lymphoma-targeted treatment may not be enough to combat their pruritus. Therefore, other itch-targeted therapies are needed for use in this disease Objective Evaluate the current evidence regarding the mechanism of action and treatments for pruritus associated with cutaneous T-cell lymphoma. Methods An explicit and thorough search was restricted to all peer-reviewed literature available through MEDLINE (1950 to September 2011) and pubmed.org. Search terms used were pruritus, cutaneous T-cell lymphoma (CTCL), mycosis fungoides (MF), and Sézary Syndrome (SS). All studies that involved pruritus in either CTCL, MF, or SS were evaluated by all three authors. Results The current literature helps to identify therapies and possible mechanisms for treating patients with CTCL associated pruritus. . Limitation Most studies were pre-clinical. Only studies involving mechanisms of action or treatment were included Conclusion A guideline is necessary to assist in the treatment of pruritus in CTCL and additional studies are necessary to uncover the exact mechanism(s) of action.

Background Qualitative data suggest that pruritus is a burdensome symptom in patients with epidermolysis bullosa (EB), but the prevalence of pruritus in children and adults with EB, as well as factors that contribute to pruritus are unknown. Objective To quantitatively identify and to characterize pruritus experienced by EB patients using a comprehensive online questionnaire. Methods A questionnaire was developed to evaluate pruritus in all ages and types of EB. Questions that characterize pruritus were included, and factors that aggravate symptoms were investigated. Patients from seven North American EB centers were invited to participate. Results A total of 146 out of 216 questionnaires were completed (response rate=68%) (73 males, 73 females; median age, 20.0). Using a 5-point Likert scale (1=never, 2=rarely, 3=sometimes, 4=often, 5=always), itchiness was the most bothersome EB complication (mean=3.3). The average daily frequency of pruritus increased with self-reported EB severity. Pruritus was most frequent at bedtime (mean=3.8) and interfered with sleep. Factors that aggravated pruritus included healing wounds, dry skin, infected wounds, stress, heat, dryness, and humidity. Conclusions Pruritus is common in EB patients and can be very bothersome. Future studies will need to investigate the most effective treatments given to EB patients for pruritus.

No abstract

The epithelial Na ؉ channel (ENaC) is implicated in the pathogenesis of salt-sensitive hypertension. Recent evidence from animal models suggests that the vasoactive peptide, endothelin (ET-1), may be an important negative regulator of ENaC in vivo. We investigated the signaling pathway involved in endothelin-mediated ENaC inhibition. Experiments were performed in NIH 3T3 cells stably expressing genes for the three (␣, ␤, and ␥) ENaC subunits. In whole cell patch clamp experiments, we found that ET-1 treatment induced a dose-dependent decrease in amiloride-sensitive currents. Using receptor-specific antagonists, we determined that the effects of ET-1 were attributed to activation of the ET B receptor. Moreover, the inhibitory effect of ET-1 on ENaC could be completely blocked when cells were pretreated with the selective Src family kinase inhibitor, PP2. Further studies revealed that basal Src family kinase activity strongly regulates ENaC whole cell currents and single channel gating. These results suggest that Src family kinases lie in a signaling pathway activated by ET-1 and are components of a novel negative regulatory cascade resulting in ENaC inhibition. Endothelin (ET)1 1, a potent vasoactive peptide originally described as an endothelial cell-derived factor, is the founding member of a family of related 21-amino acid peptides (1, 2). Each endothelin (ET-1, ET-2, and ET-3) is encoded by a distinct gene and is processed from an inactive precursor via two proteolytic cleavages to generate a biologically active peptide (3,4). Endothelins are synthesized in many cell types, including endothelial, epithelial, fibroblast, and cardiac muscle cells, and function as autocrine or paracrine factors to regulate different cellular processes (1, 5-7). The two endothelin receptors, ET A and ET B , are broadly expressed with overlapping, but distinct, distributions (8 -11). ET A and ET B are heterotrimeric G protein-coupled receptors (GPCRs) that can couple with multiple G␣ subunits, depending on cell type (12)(13)(14). In addition, ET receptors stimulate the activity of nonreceptor tyrosine kinases in some cells (5,15,16). Although this activation is generally thought to mediate the mitogenic effects of endothelins, acute activation of NHE3 via ET-1 is blocked ϳ50% by tyrosine kinase inhibitors (17, 18). The ET-mediated activation of NHE3 occurs specifically via ET B receptors (19).Recent evidence indicates that renal ET B receptors may be important for sodium handling. The function of ET B has been examined in rats with naturally occurring mutation of the ET B gene. These studies indicate that ET B plays an essential role in development of enteric neurons because absence of functional ET B receptors causes perinatal lethality resulting from megacolon (20, 21). Gariepy et al. (22) rescued this phenotype by specifically expressing ET B only in adrenergic neurons using the dopamine ␤-hydroxylase promoter (22). On high salt diets, these rats developed salt-sensitive hypertension, which was restored to normal when animals ...

No abstract

Regulation of cystic fibrosis transmembrane regulator (CFTR) and epithelial sodium channel (ENaC) in airway epithelia strongly influences the rate of mucociliary clearance (MCC) by determining the volume of airway surface liquid. MCC increases in response to stimuli originating on the airway surface, and CFTR and ENaC in airway epithelia appear to be regulated by local rather than systemic signaling. Although all signals that regulate CFTR and ENaC in airways have not been identified, the release of nucleotides from airway epithelial cells exposed to physical stimuli initiates a series of events that coordinately favor increased MCC. These events include activation of adenosine A2B receptors that stimulate CFTR and P2Y2 receptors that inhibit ENaC. Together these actions result in an increased volume of airway surface liquid and increased MCC rates. Stimulation of CFTR by A(2B)AR uses protein kinase (PK) A signaling elements that are localized within the apical/subapical compartment, including G proteins, adenylyl cyclase, PKA-II, A-kinase anchoring proteins, and phosphodiesterases. Inhibition of ENaC by P2Y2 receptors appears to be mediated by phospholipase C-beta3, possibly through an effect on the levels of phosphatidylinositol 4,5-bisphosphonate in the apical membrane.

Introduction: Treatment of early-stage mycosis fungoides (MF) requires safe, skin-directed therapies. Medication side effects can lead to underutilization of effective therapies. The objective of this study was to assess the use of topical triamcinolone 0.1% ointment as a means of reducing contact dermatitis associated with topical mechlorethamine/chlormethine gel for the treatment of MF. Methods: This prospective, randomized, openlabel study evaluated 28 adults with mycosis fungoides who were eligible for treatment with topical mechlorethamine/chlormethine gel from December 17, 2017 to December 23, 2020. Patients were treated for 4 months with clinical follow-up through 12 months. Patients had half of their lesions also treated with topical triamcinolone 0.1% ointment (while the other half were treated with mechlorethamine/chlormethine alone). The study was self-controlled with separate lesions in the same patient receiving each treatment arm. Treatment arms were determined by the flip of a coin. Results: Twenty-eight patients enrolled (17 men (61%) and 11 women (39%)). Demographics included 25 White, 2 African Americans, and 1 Asian patient. Twenty-five completed the 12-month follow-up. Triamcinolone 0.1% ointment led to increased tolerability of mechlorethamine/chlormethine gel but did not change the efficacy of mechlorethamine/chlormethine. There was a statistically significant 50% decrease in dermatitis (SCORD score) at month 2 in the triamcinolone-treated arm. Conclusions: Topical triamcinolone ointment is a helpful adjuvant therapy when treating patients with topical mechlorethamine/ chlormethine gel. It diminishes inflammation and does not reduce efficacy. The peak incidence of dermatitis in the study occurred in the second and third months. Trial Registration: ClinicalTrials.gov identifier, NCT03380026.