Quantitative analysis of cutaneous calcitonin gene-related peptide content in response to acute cutaneous mechanical or thermal stimuli and immobilization-induced stress in rats

Neuropeptides concentrations in the skin of a murine (NC/Nga mice) model of atopic dermatitis

BACKGROUND

It has been reported that the expression of neuropeptides (NPs), and the density and structure of peripheral nerves in atopic dermatitis (AD) are different from those in normal skin.

OBJECTIVE

We investigated the role of NPs, in the development of AD with quantitative study of substance P (SP) and calcitonin gene-related peptide (CGRP) in the skin of AD-model mice.

METHODS

We measured the NPs in the skin of mice (NC/Nga as AD-model mice, BALB/c and C57BL/6 as control) by enzyme-linked immunosorbentassay (ELISA). Peripheral nerve fibers and SP in the skin were stained by immunohistochemical staining, using anti-PGP9.5 antibody and anti-SP antibody.

RESULTS

Under conventional condition, SP concentration in AD-like skin lesions of NC/Nga mice was higher than that in non-affected skin of the same mice. Under specific pathogen-free condition, SP concentration in the skin of NC/Nga mice was higher than that in the skin of BALB/c and C57BL/6 mice. In contrast, CGRP concentration in the skin lesions was lower than that in non-affected skin of NC/Nga mice. SP was detected not only in the nerve fibers in the dermis but also in mast cells in the inflammatory areas.

CONCLUSIONS

The skin of NC/Nga mice contains more SP congenitally, and environmental factors may aggravate this abnormal condition. We hypothesize that increase of SP accompanied with a decrease of CGRP in the skin may play important roles in the pathogenesis and development of AD.

Interleukin-12 p40-homodimer production in sensory dorsal root ganglion neurons

Recently, the reports that sensory nerves contribute to induction and development of peripheral inflammation have been accumulating. Although neuropeptides have been thought to participate in modulation of inflammation, we supposed the involvement of cytokines. Interleukin-12 (IL-12) is a key regulator of cell-mediated immunity. IL-12 is heterodimer cytokine consisting of a p35 and a p40 subunit, but the results that some of immune cell types secrete p40-homodimer have been reported. In this study, we investigated the expression and secretion of IL-12 in mouse sensory neurons in order to evaluate the involvement of sensory neurons in cell-mediated immunity. Expression of IL-12 p40 mRNA was detected and enhanced by interferon-gamma (IFN-gamma), but another subunit of IL-12 p35 mRNA was not detected in sensory dorsal root ganglion (DRG) neurons in culture. IL-12 p40 molecule was detected in DRG neurons by immunocytochemistry. In addition, cultured DRG neurons secreted p40-homodimer that inhibited IL-12-induced STAT4 phosphorylation in T cells. p40 mRNA expression was accumulated in DRG after administration of IFN-gamma into mouse footpad, and this enhancement was eliminated by a cut of sciatic nerve. These results suggest the possibility that p40-homodimer derived from sensory nerves suppresses the excessive peripheral inflammation.

Involvement of vanilloid receptors in heat stress-induced delayed protection against myocardial ischemia-reperfusion injury

Sprague-Dawley rats were pretreated with whole body hyperthermia (rectal 42 degrees C) for 15 min, 24 h before the experiments, and then the left main coronary artery of rat hearts was subjected to a 60 min occlusion followed by 3 h reperfusion. Myocardium injury degree was evaluated by measurement of infarct size and serum creatine kinase (CK) activity. Plasma concentrations of calcitonin gene-related peptide (CGRP), and the expression of alpha- and beta-CGRP mRNA in dorsal root ganglia were determined by radioimmunoassay and semi-quantitative reverse-transcription polymerase chain reaction, respectively. Hyperthermia treatment significantly reduced infarct size and CK release concomitantly with a dramatic increase in plasma concentrations of CGRP and the expression of alpha-CGRP mRNA, but not beta-CGRP mRNA, which was completely abolished by pretreatment with capsazepine (38 mg/kg, s.c.), a competitive vanilloid receptor 1 antagonist. These results suggests that vanilloid receptor 1 on capsaicin-sensitive sensory nerves plays an important role in the modulation of the delayed cardioprotection induced by heat stress in rats.

Involvement of alpha-calcitonin gene-related peptide in heat stress-induced delayed preconditioning in rat hearts

1. Previous studies have shown that hyperthermia is capable of activating capsaicin-sensitive sensory nerves and stimulating the release of neurotransmitters from their peripheral terminals. Calcitonin gene-related peptide (CGRP) has recently been found to participate in delayed cardioprotection in rat isolated hearts. 2. The purpose of the present study was to explore whether the delayed cardioprotection by heat stress in vivo involves the expression and release of CGRP. 3. Sprague-Dawley rats were pretreated with whole-body hyperthermia (rectal 42 degrees C) for 15 min, 24 h before the experiments and then the left main coronary artery of rat hearts was subjected to a 45 min occlusion followed by 3 h reperfusion. The degree of myocardial injury was evaluated by measurement of infarct size and plasma creatine kinase (CK) activity. The plasma levels of CGRP and expression of CGRP (alpha and beta isoforms) mRNA in lumbar dorsal root ganglia at 4, 8, 16 or 24 h after heat stress treatment were measured. 4. Pretreatment with hyperthermia significantly reduced infarct size and CK release. Heat stress also significantly increased plasma concentrations of CGRP and the expression of alpha-CGRP mRNA, but not beta-CGRP mRNA. The effect of heat stress was completely abolished by pretreatment with capsaicin (50 mg/kg, s.c.), which selectively depletes transmitters in capsaicin-sensitive sensory nerves. 5. In summary, the results suggest that the delayed cardioprotection by heat stress involves the synthesis and release of CGRP and that the protection is mainly mediated by the alpha-CGRP isoform.

The cardioprotection of calcitonin gene-related peptide-mediated preconditioning

Preconditioning induced by brief ischemia or hyperthermia or some drugs shows two phases, early and delayed protection. The cardioprotection afforded by preconditioning is related to stimulation of endogenous mediators release. Calcitonin gene-related peptide (CGRP), a major transmitter of capsaicin-sensitive sensory nerves, has recently been shown to play an important role in mediation of the preconditioning induced by brief ischemia or hyperthermia or by some drugs, and alpha-CGRP seems to play a major role in the mediation of delayed preconditioning. It has been shown that the cardioprotection afforded by CGRP-mediated preconditioning is due to inhibition of cardiac tumor necrosis factor-alpha (TNF-alpha) production, but not to the activation of the K(ATP) channel.

Langerhans cells in the neuro-immuno-cutaneous system

Langerhans cells are epidermal antigen presenting cells. They are able to express some neuronal markers. They express many neuropeptide receptors. Neuropeptides are able to modulate Langerhans cell functions. Langerhans cells are closely connected with nerve fibers in the epidermis. Thus, Langerhans cells and the nervous system are anatomically and functionally associated. We suggest that they belong to a neuroimmunocutaneous system. The interactions between nervous and immune system are probably important in the pathophysiogeny of inflammatory dermatoses.

Modulatory effect of L-NAME, a specific nitric oxide synthase (NOS) inhibitor, on stress-induced changes in plasma adrenocorticotropic hormone (ACTH) and corticosterone levels in rats: physiological significance of stress-induced NOS activation in hypothalamic-pituitary-adrenal axis

We investigated whether NG-nitro-L-arginine methyl ester (L-NAME), a specific inhibitor of nitric oxide synthase (NOS), can modify the stress-induced adrenocorticotropic hormone (ACTH) and corticosterone responses, because we found that immobilization-induced stress increases NOS mRNA and protein levels and enzyme activity in the adrenal cortex. The physiological significance of these phenomena, however, remains unknown. Plasma ACTH and corticosterone levels were determined by radioimmunoassay (RIA) of systemic blood samples and NOS enzyme activity was measured as the rate of [3H]arginine conversion to [3H]citrulline in the presence of tissue homogenate of adrenal cortex separated from the adrenal gland. The NOS enzyme activity in the adrenal cortex of rats pre-injected with saline at 2 h after the 2-h immobilization was significantly higher (P < 0.01) than that in the non-stressed controls. Pre-injection of L-NAME (100 mg/kg, s.c.) almost completely abolished the activity. This dose of L-NAME maintained a significantly elevated plasma corticosterone level (P < 0.05, compared with basal level) even 2 h after the 2-h stress, whereas the plasma corticosterone level in rats pre-injected with saline returned to the basal level at the same time point. Plasma ACTH level in L-NAME-pre-treated rats was higher than that in those pre-treated with saline 2 h after the stress, but the difference was not significant. This dose of L-NAME did not influence plasma ACTH or corticosterone levels under resting conditions without stress. These findings suggest that the stress-induced increase in NO synthesis in the adrenal cortex can modify the stress-induced corticosterone response to facilitate the recovery from the elevated corticosterone secretion by stress in the adrenal cortex to the resting basal level.