Involvement of calcitonin gene-related peptide in elevation of skin temperature in castrated male rats

Virtual drug repurposing study for the CGRPR identifies pentagastrin and leuprorelin as putative candidates

Calcitonin gene-related peptide receptor (CGRPR) is a heterodimer consisting of CLR and RAMP1 proteins. Activation of the CGRPR with the endogenous peptide CGRP is known to play a crucial role in migraine pathophysiology. CGRP occupies two regions in the CGRPR upon binding, namely ectodomain and transmembrane sites (sites 1 and 2, respectively). The disruption of the CGRPR heterodimer interface is one of the main strategies to prevent CGRPR activation and its resulting effects. So far, FDA approved monoclonal antibodies and small molecule gepant inhibitors are considered for the treatment of acute or chronic migraine symptoms. However, most of these gepants have severe side effects. Thus, in this study, a virtual drug repurposing approach is applied to CGRPR to find alternative or better molecules that would have a potential to inhibit or block the CLR - RAMP1 interface compared to known gepant molecules. A small molecule library of FDA-approved molecules was screened in these two different binding sites, further simulations were performed and analyzed. The objectives of this study are (i) to repurpose an FDA-approved drug having more potent features for CGRPR inhibition compared to gepants, and (ii) to examine whether the transmembrane binding site (site 2) accepts small molecules or small peptide analogues for binding. As a result of this extensive in silico analysis, two molecules were identified, namely pentagastrin and leuprorelin. It is shown that FDA approved compound rimegepant and the identified pentagastrin molecules form and maintain the interactions through CLR W72 and RAMP1 W74, which are the residues revealed to have an important role in CGRPR antagonism at binding site 1. At binding site 2, the interactions needed to be formed for CGRP binding are not captured by rimegepant nor leuprorelin, yet leuprorelin forms more interactions throughout the simulations, meaning that small molecules are also capable of binding to site 2. Moreover, it is found that the crucial interactions for receptor signaling and heterodimerization occurred between CLR and RAMP1 interface are disrupted more with the ligands bound to ectodomain site, rather than the transmembrane domain. These findings of pentagastrin and leuprorelin molecules are recommended to be considered in further de novo drug development and/or experimental studies related to CGRPR signaling blockade and antagonism.

Role of calcitonin gene-related peptide in energy metabolism

PURPOSE

Calcitonin gene-related peptide (CGRP) is a neuropeptide produced by alternative tissue-specific splicing of the primary transcript of the CALC genes. CGRP is widely distributed in the central and peripheral nervous system, as well as in several organs and tissues. The presence of CGRP in the liver and brown and white adipose tissue suggests an effect of this neuropeptide on regulation of energy homeostasis.

METHODS

In this review, we summarize the current knowledge of the effect of CGRP on the control of energy metabolism, primarily focusing on food intake, thermoregulation and lipid metabolism in adipose tissue, liver and muscle.

RESULTS

CGRP induces anorexia, stimulating anorexigenic neuropeptide and/or inhibiting orexigenic neuropeptide expression, through cAMP/PKA pathway activation. CGRP also induces energy expenditure, increasing the skin temperature and brown adipose tissue thermogenesis. It has been also suggested that information related to peripheral lipid stores may be conveyed to the brain via CGRP-sensory innervation from adipose tissue. More recently, it was demonstrated that mice lacking αCGRP are protected from obesity induced by high-fat diet and that CGRP regulates the content of lipid in liver, muscle and adipose tissue.

CONCLUSIONS

It is unclear the receptor responsible by CGRP effects, as well as whether this neuropeptide acts directly or indirectly in liver, muscle and adipose tissue.

A timecourse analysis of systemic and gonadal effects of temperature on sexual development of the red-eared slider turtle Trachemys scripta elegans

Temperature dependent sex determination (TSD) is the process by which the environmental temperature experienced during embryogenesis influences the sex of an organism, as in the red-eared slider turtle Trachemys scripta elegans. In accord with current paradigms of vertebrate sex determination, temperature is believed to exert its effects on sexual development in T. scripta entirely within the middle third of development, when the gonad is forming. However, whether temperature regulates the transcriptome in T. scripta early embryos in a manner that could influence secondary sex characteristics or establish a pro-male or pro-female environment has not been investigated. In addition, apart from a handful of candidate genes, very little is known about potential similarities between the expression cascade during TSD and the genetic cascade that drives mammalian sex determination. Here, we conducted an unbiased transcriptome-wide analysis of the effects of male- and female-promoting temperatures on the turtle embryo prior to gonad formation, and on the gonad during the temperature sensitive period. We found sexually dimorphic expression reflecting differences in steroidogenic enzymes and brain development prior to gonad formation. Within the gonad, we mapped a cascade of differential expression similar to the genetic cascade established in mammals. Using a Hidden Markov Model based clustering approach, we identified groups of genes that show heterochronic shifts between M. musculus and T. scripta. We propose a model in which multiple factors influenced by temperature accumulate during early gonadogenesis, and converge on the antagonistic regulation of aromatase to canalize sex determination near the end of the temperature sensitive window of development.

Physiology and Endocrinology of Hot Flashes in Prostate Cancer

The purpose of this article is to integrate the physiology of the male reproductive system and the role of hormones in the pathophysiology and treatment of prostate cancer. The primary focus is to review hormonal changes associated with androgen ablation treatment and to integrate the available hormonal data into a hypothesis. This review used a systematic search of Medline references from 1990 to 2006. All sources were critically evaluated to arrive at an understanding of androgen deprivation symptoms, such as hot flushes/flashes, and to identify research needed in this area. Research is needed to explore the physiological mechanisms of hot flashes to develop better therapeutic treatment options to ameliorate side effects of hormonal treatment. Studies are needed to investigate all aspects of hot flashes in populations other than those with breast cancer, such as men with prostate cancer, carcinoid tumors, medullary thyroid tumors, pancreatic islet-cell tumors, renal cell carcinoma, and phenochromocytoma.

Risk factors, pathophysiology, and treatment of hot flashes in cancer

Hot flashes are prevalent and severe symptoms that can interfere with mood, sleep, and quality of life for women and men with cancer. The purpose of this article is to review existing literature on the risk factors, pathophysiology, and treatment of hot flashes in individuals with cancer. Electronic searches were conducted to identify relevant English-language literature published through June 15, 2012. Results indicated that risk factors for hot flashes in cancer include patient-related factors (eg, age, race/ethnicity, educational level, smoking history, cardiovascular risk including body mass index, and genetics) and disease-related factors (eg, cancer diagnosis and dose/type of treatment). In addition, although the pathophysiology of hot flashes has remained elusive, these symptoms are likely attributable to disruptions in thermoregulation and neurochemicals. Therapies that have been offered or tested fall into 4 broad categories: pharmacological, nutraceutical, surgical, and complementary/behavioral strategies. The evidence base for this broad range of therapies varies, with some treatments not yet having been fully tested or showing equivocal results. The evidence base surrounding all therapies is evaluated to enhance hot flash treatment decision-making by clinicians and patients.

Dong Quai (angelica sinensis) in the treatment of hot flashes for men on androgen deprivation therapy: results of a randomized double-blind placebo controlled trial

OBJECTIVE

To determine whether Dong Quai, a Chinese herbal compound purported to be efficacious in treating menopausal vasomotor symptoms, has a therapeutic benefit in treating hot flashes among prostate cancer patients receiving androgen deprivation therapy.

METHODS

A randomized double-blind placebo controlled trial was conducted involving 22 men receiving luteinizing hormone-releasing hormone agonist therapy for prostate cancer with bothersome hot flashes. After recording a baseline log of the frequency, duration and severity of daily hot flashes, patients were randomly assigned in a 1:1 ratio to receive daily placebo or Dong Quai for 3 months. Vasomotor and adverse events were recorded daily. Blood work including serum prostate-specific antigen (PSA), international normalized ratio of prothrombin time and partial thromoboplastin time were recorded at baseline and at the termination of the study.

RESULTS

Seventeen of the 22 patients enrolled completed the trial. Baseline vasomotor duration and severity were equivalent between the groups, however the number of hot flashes were significantly more in the Dong Quai group (p = 0.02). With respect to the change in number of hot flashes per day, there was a slight decrease in the mean number among the Dong Quai group which was insignificant. The absolute change and average percentage change in perceived hot flash severity was similar in both groups. There was no significant decrease in the duration of the hot flashes between the 2 groups. Disease progression based on either PSA increase or change in digital rectal exam was not observed in any patient.

CONCLUSION

In this small pilot study, there were no significant differences in the severity, frequency or duration of hot flashes among men receiving placebo or Dong Quai.

Calcitonin gene-related peptide alters the firing rates of hypothalamic temperature sensitive and insensitive neurons

Background

Transient hyperthermic shifts in body temperature have been linked to the endogenous hormone calcitonin gene-related peptide (CGRP), which can increase sympathetic activation and metabolic heat production. Recent studies have demonstrated that these centrally mediated responses may result from CGRP dependent changes in the activity of thermoregulatory neurons in the preoptic and anterior regions of the hypothalamus (POAH).

Results

Using a tissue slice preparation, we recorded the single-unit activity of POAH neurons from the adult male rat, in response to temperature and CGRP (10 μM). Based on the slope of firing rate as a function of temperature, neurons were classified as either warm sensitive or temperature insensitive. All warm sensitive neurons responded to CGRP with a significant decrease in firing rate. While CGRP did not alter the firing rates of some temperature insensitive neurons, responsive neurons showed an increase in firing rate.

Conclusion

With respect to current models of thermoregulatory control, these CGRP dependent changes in firing rate would result in hyperthermia. This suggests that both warm sensitive and temperature insensitive neurons in the POAH may play a role in producing this hyperthermic shift in temperature.

Breast and infant temperatures with twins during shared Kangaroo Care

Kangaroo Care has been shown to keep a singleton preterm infant warm by body heat generated in maternal breasts that is conducted to the infant. No studies have examined whether twins simultaneously receiving Kangaroo Care, called Shared Kangaroo Care, are sufficiently warm and how the breasts respond to twin presence. Two case studies were done to determine the temperatures of twins being simultaneously kangarooed and the temperatures of maternal breasts during Shared Kangaroo Care. Two sets of premature twins were held in Shared Kangaroo Care for 1.5 hours. Infant temperatures were recorded from incubators; breast temperatures were recorded from thermistors. Infant temperatures remained warm and increased during Kangaroo Care, and each breast appeared to respond to the thermal needs of the infant on that breast. Physiological explanations for thermal synchrony exist. These data suggest that twins can be simultaneously held in Kangaroo Care without thermal compromise because each breast responds individually to the infant's thermal needs.

State of the science: hot flashes and cancer. Part 1: definition, scope, impact, physiology, and measurement

PURPOSE/OBJECTIVES

To critically evaluate and synthesize multidisciplinary research related to hot flashes in the context of cancer. Topics include the definition, scope, and impact of hot flashes; physiologic mechanisms; and measurement issues.

DATA SOURCES

Published, peer-reviewed articles and textbooks; editorials; unpublished data; and computerized databases.

DATA SYNTHESIS

Hot flashes can affect a diverse group of men and women diagnosed with or at high risk for certain cancers with a resulting negative impact on quality of life. Although the exact physiologic mechanisms underlying hot flashes remain unclear, a complex interplay of thermoregulatory, gluconeuroendocrine, genetic, and behavioral factors appears to be involved. Measurement of hot flashes should be considered carefully because they can be operationalized objectively and subjectively.

CONCLUSIONS

The large and diverse evidence base and current national attention on measurement of hot flashes highlight the importance of the symptom to healthcare professionals, including oncology nurses.

IMPLICATIONS FOR NURSING

Careful attention to assessment and measurement of hot flashes in patients with cancer is needed.

Prevention by 17β-estradiol and progesterone of calcitonin gene-related peptide-induced elevation of skin temperature in castrated male rats

OBJECTIVES

To clarify the relationship between calcitonin gene-related peptide (CGRP) and ovarian hormones (17beta-estradiol and progesterone) in hot flashes in men who undergo androgen deprivation therapy for prostate cancer, we studied the effects of ovarian hormones on CGRP-induced elevation of skin temperature in castrated male rats. The results were compared with those from rats treated with testosterone replacement.

METHODS

Adult male rats were castrated by either a single injection of gonadotropin-releasing hormone analogue (Leuplin, 1.0 mg/kg, subcutaneously) or bilateral orchiectomy. The castrated animals were subcutaneously injected daily for 14 days with ovarian hormones, testosterone, or olive oil as the vehicle. On the day after the final administration of the drug, the changes in skin temperature induced by exogenous CGRP (10 mug/kg intravenously), serum testosterone concentration, and prostate weight were measured.

RESULTS

The CGRP-induced elevation of skin temperature was significantly greater in the castrated rats than in the sham-treated rats. This potentiation was significantly inhibited by treatment with ovarian hormones, as well as by testosterone replacement. The testosterone replacement restored decreases in both the serum testosterone level and the prostate weight due to castration; the treatment with ovarian hormones did not affect them.

CONCLUSIONS

17beta-Estradiol and progesterone, which do not confer testosterone activity on serum, may be useful for the treatment of hot flashes in patients for whom testosterone replacement therapy is contraindicated, such as those with prostate carcinoma. In addition, we suggest that CGRP is closely involved in the amelioration of hot flashes by ovarian hormones in men who undergo androgen deprivation therapy.