Calcitonin gene-related peptide (CGRP) is thought to be a prominent neuropeptide in cardiovascular regulation and neuroimmune modulation. There are two isoforms of CGRP (␣CGRP and ␤CGRP), and the main CGRP receptors are probably composed of a calcitonin receptor-like receptor (CLR) and a receptor activity-modifying protein (RAMP)1. However, the physiological functions of CGRP that are mediated through the CLR/RAMP1 receptors remain to be clarified. For an improved understanding of the functions, we generated mice deficient in RAMP1, a specific subunit of CGRP receptors, by a conditional gene-targeting technique. The RAMP1-deficient mice (RAMP1 ؊/؊ ) exhibited high blood pressure, with no changes in heart rate. ␣CGRP was found to have a potent vascular relaxant activity compared with ␤CGRP in the artery of the WT (RAMP1 ؉/؉ ) mice. The activities of both CGRP isoforms were remarkably suppressed in the arteries of the RAMP1 ؊/؊ mice. The LPS-induced inflammatory responses of the RAMP1 ؊/؊ mice revealed a transient and significant increase in the serum CGRP levels and high serum levels of proinflammatory cytokines compared with the RAMP1 ؉/؉ mice. ␣CGRP and ␤CGRP equally suppressed the production of TNF-␣ and IL-12 in bone marrow-derived dendritic cells stimulated with lipopolysaccharide. Their inhibitory effects were not observed in the bone marrow-derived dendritic cells of the RAMP1 ؊/؊ mice. These results indicate that CGRP signaling through CLR/RAMP1 receptors plays a crucial role in the regulation of both blood pressure by vascular relaxation and proinflammatory cytokine production from dendritic cells.gene-disrupted mice ͉ calcitonin gene-related peptide ͉ adrenomedullin ͉ neuropeptide ͉ dendritic cells C alcitonin gene-related peptide (CGRP) is a 37-aa neuropeptide that is produced in the neural body of dorsal root ganglion cells and released from sensory nerve endings. There are two isoforms of CGRP: ␣ and ␤ in rats and mice and I and II in humans. These differ in their peptide sequences by 1 aa (rats) and 3 aa (mice and humans) of the 37 aa (1). ␣CGRP is produced mainly in the nervous system by the tissue-specific alternative splicing of the primary RNA transcript of the calcitonin/CGRP gene. On the other hand, ␤CGRP is produced not only in the neuronal tissues but also in the enteric nerves of the intestine (2) and in immune cells such as T cells (3). Pharmacologically, ␣CGRP is known to have the most potent vasodilatory activity (4). Most blood vessels are surrounded by a dense perivascular CGRPergic neural network, suggesting the physiological importance of CGRP in vasodilatory regulation (5). ␣CGRP also contributes to local neurogenic inflammation and nociception (6). Moreover, the functions of immune cells such as macrophages (7,8), Langerhans cells (8), and T cells (9, 10) are modulated by ␣CGRP. However, the precise functional differences between ␣CGRP and ␤CGRP remain unclear.Historically, CGRP receptors have been classified into two classes: CGRP 1 and CGRP 2 receptors. The CGRP 1 receptors are m...

Royal jelly (RJ) produced by honey bees is known to contain three major nutrients including amino acids, vitamins and minerals.1) Additionally, RJ has various biological activities such as a hypotensive effect, insulin-like action and antitumor activity.2-4) Therefore, it is possible that RJ may have some effects on insulin resistance, which is considered to be a cause of various lifestyle-related diseases. Many clinical studies have shown a possible relationship between hypertension and insulin resistance, since patients with type 2 (noninsulin dependent) diabetes mellitus frequently have insulin resistance associated with hypertension. 5-7)Chronic administration of fructose to rats has been reported to cause insulin resistance, which is characterized by increased serum insulin and euglycemia.8) Especially, a hyperinsulinemic state associated with hypertension was more prominently induced by fructose drinking than by fructose feeding.9) Previously, we reported that rats with chronic hyperinsulinemia, which was induced by giving a 15% fructose solution in drinking water for 10 weeks (fructose-drinking rats, FDR), showed deficient neuronal regulation of vascular tone, and this leads to hypertension. 10,11) Recently, we demonstrated that chronic administration of RJ prevented development of insulin resistance in Ohtsuka Long-Evanse Fatty (OLETF) rats, which is a spontaneous type 2 diabetic model. 12)Thus, in the present study, we investigated the effects of RJ on the insulin resistance in FDR. We also examined whether RJ prevents hypertension and altered vascular responsiveness induced by insulin resistance using isolated mesenteric vascular beds of rats. MATERIALS AND METHODS AnimalsSix week-old male Wistar rats were used in this study. They were given 15% fructose solution as drinking water ad libitum for 8 weeks. The control group was given tap water instead of 15% fructose solution. Three rats were housed in each cage (W 220ϫL 320ϫH 135 mm; Natsume Seisakusho, Tokyo, Japan), and given normal rat chow (Oriental Yeast, Tokyo, Japan). They were housed in the Animal Research Center of Okayama University at a controlled ambient temperature of 22Ϯ2°C with 50Ϯ10% relative humidity and with a 12-h light/12-h dark cycle (lights on at 8:00 a.m.). This study was carried out in accordance with the Guidelines for Animal Experiments at Okayama University Advanced Science Research Center, Japanese Government Animal Protection and Management Law (No. 105) and the Japanese Government Notification on Feeding and Safekeeping of Animals (No. 6). Every effort was made to minimize the number of animals used and their suffering.Long-Term Administration of RJ RJ, which was enzymatically treated and supplied by Yamada Apiculture Center, Inc. (Okayama, Japan) (Lot No. 020605), was used in this study. RJ was diluted by adding distilled water and orally administered at doses of 100 mg/kg/d and 300 mg/kg/d for 8 weeks from 6 to 14 weeks of age. Each animal was lightly anesthetized with ether and orally administrated RJ solution at a volum...

We have shown previously that stimulation of the angiotensin II type 2 receptor (AT2R) results in nerve facilitation. In this study, we determined the capacity of candesartan to correct expression patterns characteristic of neuropathy and AT2R-mediated neurite outgrowth in the fructose-induced insulin-resistant rat, which is one of the human hyperinsulinemia models. Wistar rats received a 15% (w/v) fructose solution in their drinking water for 4 weeks (fructose-drinking rats [FDRs]), with or without candesartan (5 mg/kg/day). We evaluated physiological and behavioral parameters and performed immunohistochemical studies. We found that the FDR developed insulin resistance and downregulated both AT2R neuronal function and phosphorylated Akt expression in dorsal root ganglia (DRG) neurons. Candesartan improved neurite outgrowth in the FDR, which was associated with the restoration of AT2R and phosphorylated Akt expression. Furthermore, downregulation of phosphoinositide 3-kinase (PI3K) inhibited AT2R-mediated neurite outgrowth in control DRG cells. PI3K activation increased AT2R-mediated neurite outgrowth and phosphorylated Akt expression in FDR DRG cells. These results suggest that the decrease of AT2R-mediated neurite outgrowth in FDRs is likely to be the result of decreased PI3K-dependent Akt activation. Candesartan improved AT2R neuronal function and Akt phosphorylation, which were associated with sensory nerve defects and insulin sensitivity in the FDR.

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