Effects of the vasoactive neuropeptides calcitonin gene-related peptide, substance P and vasoactive intestinal polypeptide on skin temperature in ovariectomized rats

Is calcitonin gene-related peptide a modulator of menopausal vasomotor symptoms?

PURPOSE

Calcitonin gene-related peptide (CGRP) is a neuropeptide widely distributed in the central and peripheral nervous systems, which is known as a potent vasodilator. Postmenopausal women who experience hot flushes have high levels of plasma CGRP, suggesting its involvement in menopausal vasomotor symptoms.

METHODS

In this review, we describe the biochemical aspects of CGRP and its effects associated with deficiencies of sexual hormones on skin temperature, vasodilatation, and sweating as well as the possible peripheral and central mechanisms involved in these events.

RESULTS

Several studies have shown that the effects of CGRP on increasing skin temperature and inducing vasodilatation are potentiated by a deficiency of sex hormones, a common condition of postmenopausal women. Additionally, the medial preoptic area of the hypothalamus, involved in thermoregulation, contains over 25-fold more CGRP-immunoreactive cells in female rodents compared with male rodents, reinforcing the role of female sex hormones on the action of CGRP. Some studies suggest that ovarian hormone deficiency decreases circulating endogenous CGRP, inducing an upregulation of CGRP receptors. Consequently, the high CGRP receptor density, especially in blood vessels, amplifies the stimulatory effects of this neuropeptide to raise skin temperature in postmenopausal women during hot flushes.

CONCLUSIONS

The duration of the perception of each hot flush in a woman is brief, while local reddening after intradermal administration of α-CGRP persists for 1 to 6 h. This contrast remains unclear.

Long distance runners present upregulated sweating responses than sedentary counterparts

Relatively few studies have investigated peripheral sweating mechanisms of long-distance runners. The aim of this study was to compare peripheral sweating mechanisms in male long-distance runners, and sedentary counterparts. Thirty six subjects, including 20 sedentary controls and 16 long-distance runners (with 7-12 years of athletic training, average 9.2±2.1 years) were observed. Quantitative sudomotor axon reflex testing (QSART) with iontophoresis (2 mA for 5 min) and 10% acetylcholine (ACh) were performed to determine axon reflex-mediated and directly activated (DIR, muscarinic receptor) sweating. Sweat onset time, sweat rate, number of activated sweat glands, sweat output per gland and skin temperature were measured at rest while maximum oxygen uptake (VO2max) were measured during maximal cycling. Sweat rate, activated sweat glands, sweat output per gland, skin temperature and VO2max were significantly higher in the trained runners than in the sedentary controls. Sweat onset time was significantly shorter for the runners. In the group of long-distance runners, significant correlations were found between VO2max and sweat onset time (r2 = 0.543, P<0.01, n = 16), DIR sweat rate (r2 = 0.584, P<0.001, n = 16), sweat output per gland (r2 = 0.539, P<0.01, n = 16). There was no correlation between VO2max and activated sweat glands. These findings suggest that habitual long-distance running results in upregulation of the peripheral sweating mechanisms in humans. Additional research is needed to determine the molecular mechanism underlying these changes. These findings complement the existing sweating data in long-distance runners.

The TU-025 keishibukuryogan clinical trial for hot flash management in postmenopausal women: results and lessons for future research

OBJECTIVE

The aim of this study was to assess the efficacy of TU-025, keishibukuryogan, a Japanese prescription herbal medicine used for hot flash management, in American women.

METHODS

This randomized, double-blind, placebo-controlled, phase II trial enrolled 178 postmenopausal women aged 45 to 58 years with a Mayo hot flash score greater than 28 per week who met other inclusion criteria. After a 1-week placebo run-in period, participants were randomly assigned placebo, or 7.5 g/day, or 12.5 g/day groups, for 12 weeks. Primary and secondary outcomes were measured using the Mayo Clinic Hot Flash Diary, the Greene Climacteric Index, and the Pittsburgh Sleep Quality Index.

RESULTS

At 3 months, hot flash scores, climacteric symptoms, and sleep quality improved by 34% in the placebo group, 40% in the 7.5 g/day group, and 38% in the 12.5 g/day group. (P < 0.001). However, the differences in changes between groups were not statistically significant (P = 0.990). Diarrhea unexpectedly developed in 20% of participants receiving active medication.

CONCLUSIONS

For American women, unlike the clinical experience for Japanese women, TU-025 did not significantly reduce the frequency and severity of hot flash symptoms, improve climacteric symptoms, or benefit sleep quality. This study identified several potentially significant methodological factors to be considered in future scientific assessments of traditional Asian medicines.

Significance of measured elevation of skin temperature induced by calcitonin gene-related peptide in anaesthetized rats

To assess whether peripheral changes related to skin temperature rise were induced by ovarian hormone deficiency, we investigated the effects of anaesthesia on calcitonin gene-related peptide (CGRP)- or luteinizing hormone-releasing hormone (LH-RH)-induced elevation of skin temperature in female rats. CGRP was used as an inducer of peripherally-mediated elevation of skin temperature, whereas LH-RH was used as an inducer of centrally-mediated elevation of skin temperature. Intravenous (i.v.) but not intracerebroventricular injection of CGRP (10 μg kg−1) or intracerebroventricular but not intravenous injection of LH-RH (10 μg/rat) elevated the skin temperature of unanaesthetized rats restrained in a Ballman's cage. The elevation with LH-RH was completely inhibited by urethane anaesthesia, whereas the elevation with CGRP was not. These results suggested that changes in skin temperature measured under anaesthesia reflected a peripherally rather than a centrally mediated mechanism. The CGRP (1.0–30 μg kg−1, i.v.)-induced elevation of skin temperature was potentiated in ovariectomized rats and inhibited by pretreatment with a CGRP receptor antagonist CGRP8–37 (1000 μg kg−1, i.v.), suggesting that the potentiation may participate in peripheral factors such as a postsynaptic hypersensitivity to CGRP following ovarian hormone deficiency. Thus, measurement of skin temperature in the anaesthetized rat was a useful procedure to seek the peripheral mechanism of potentiation of skin temperature induced by CGRP, thought to be closely related to menopausal hot flashes.

Effects of the traditional Japanese medicine Tokaku-jyoki-to in rat-models for menopausal hot flash

AIM OF STUDY

Luteinizing hormone-releasing hormone (LH-RH) has been suggested as an inducer of centrally mediated elevation of skin temperature, and calcitonin gene-related peptide (CGRP) is one of the potent vasodilator neuropeptides that has been suggested as an inducer of peripherally mediated elevation of skin temperature. We investigate the effect of the Japanese herbal medicine Tokaku-jyoki-to using two rat-models for menopausal hot flash.

MATERIALS AND METHODS

Tokaku-jyoki-to used in present study was prepared as a spray-dried powder from hot-water extract. Skin temperature was measured by thermister thermometer. Estrogen receptor (ER) binding assay of Tokaku-jyoki-to extract was performed using human recombinant ERalpha or ERbeta.

RESULTS

Oral Tokaku-jyoki-to (1000 mg/kg) restored skin temperature rise induced by LH-RH or CGRP in ovariectomized (OVX) rats as well as subcutaneous 17beta-estradiol (0.010 mg/kg) did. Tokaku-jyoki-to did not affect the lower concentration of plasma estradiol and the decreased uterine weight due to ovariectomy, although the hormone replacement of 17beta-estradiol restored them. In estrogen receptor ligand-binding study, Tokaku-jyoki-to extract bound to human ERalpha poorly and did not bound to human ERbeta.

CONCLUSIONS

These results suggest that Tokaku-jyoki-to, which appears to contain organ-specific selective estrogen receptor modulator, may be useful for the treatment of hot flashes in patients for whom estrogen replacement therapy is contraindicated as well as menopausal women.

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.

Changes in breast skin temperature during the course of breastfeeding

Breast skin temperature was measured during breastfeeding in 11 mothers on a total of 47 occasions, using a Coretemp CM-210 (Terumo Corp, Tokyo, Japan), to examine the changes of breast skin temperature during the course of breastfeeding. In both breasts, the breast skin temperature was significantly higher than the baseline skin temperature from the beginning of suckling up to 5 minutes after completion of suckling, and the mean breast skin temperature before breastfeeding between 4 days and 8 weeks postpartum was significantly higher than that on the first 1 to 2 days postpartum. These results show that the breast skin temperature increases between the first 1 to 2 days and 4 to 5 days postpartum and that breast skin temperature remains high during suckling and up to 5 minutes after the completion of suckling. These findings will be useful for educating mothers during the perinatal period on the normal course of breastfeeding by individual instruction or in classes.

Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ

This review focuses on the role of the peripheral nervous system in cutaneous biology and disease. During the last few years, a modern concept of an interactive network between cutaneous nerves, the neuroendocrine axis, and the immune system has been established. We learned that neurocutaneous interactions influence a variety of physiological and pathophysiological functions, including cell growth, immunity, inflammation, pruritus, and wound healing. This interaction is mediated by primary afferent as well as autonomic nerves, which release neuromediators and activate specific receptors on many target cells in the skin. A dense network of sensory nerves releases neuropeptides, thereby modulating inflammation, cell growth, and the immune responses in the skin. Neurotrophic factors, in addition to regulating nerve growth, participate in many properties of skin function. The skin expresses a variety of neurohormone receptors coupled to heterotrimeric G proteins that are tightly involved in skin homeostasis and inflammation. This neurohormone-receptor interaction is modulated by endopeptidases, which are able to terminate neuropeptide-induced inflammatory or immune responses. Neuronal proteinase-activated receptors or transient receptor potential ion channels are recently described receptors that may have been important in regulating neurogenic inflammation, pain, and pruritus. Together, a close multidirectional interaction between neuromediators, high-affinity receptors, and regulatory proteases is critically involved to maintain tissue integrity and regulate inflammatory responses in the skin. A deeper understanding of cutaneous neuroimmunoendocrinology may help to develop new strategies for the treatment of several skin diseases.

Anti-inflammatory actions of acupuncture

Acupuncture has a beneficial effect when treating many diseases and painful conditions, and therefore is thought to be useful as a complementary therapy or to replace generally accepted pharmacological intervention. The attributive effect of acupuncture has been investigated in inflammatory diseases, including asthma, rhinitis, inflammatory bowel disease, rheumatoid arthritis, epicondylitis, complex regional pain syndrome type 1 and vasculitis. Large randomised trials demonstrating the immediate and sustained effect of acupuncture are missing. Mechanisms underlying the ascribed immunosuppressive actions of acupuncture are reviewed in this communication. The acupuncture-controlled release of neuropeptides from nerve endings and subsequent vasodilative and anti-inflammatory effects through calcitonine gene-related peptide is hypothesised. The complex interactions with substance P, the analgesic contribution of beta-endorphin and the balance between cell-specific pro-inflammatory and anti-inflammatory cytokines tumour necrosis factor-alpha and interleukin-10 are discussed.