糖尿病相关VPAC、PAC受体及其药物研发的进展

VPAC、PAC受体是近年发现的开发2型糖尿病药物的重要靶标,垂体腺苷酸环化酶激活多肽(PACAP)、血管活性肠肽(VIP)则是它们的天然配体,与受体结合激活后能促进葡萄糖依赖性胰岛素分泌,既能保护细胞又不引起胰高血糖素分泌和糖原分解,因此其配体相关化合物的开发研究成为开发2型糖尿病药物的重要方向。目前针对VPAC、PAC受体开发的配体类似物主要包括了肽类和非肽类小分子两大类,但它们仍然存在诸多不足,至今仅有一个药物进入到临床研究阶段。本综述系统总结了目前针对VPAC、PAC受体为靶标的肽类和非肽小分子药物的开发研究现状,可为将来此类药物的研发提供参考。     

VPAC2在CHO细胞的表达及鉴定

PAC2是垂体腺苷酸环化酶激活多肽(Pituitary adenylate cyclase activating polypeptide,PACAP)和血管活性肠肽(vasoactive intestinal peptide,VIP)的共同受体,介导多种重要生物学功能。为获得稳定特异表达VPAC2的中国仓鼠卵巢(Chinesehamsterovary,CHO)细胞,将pcDNA-VPAC2表达载体转染CHO细胞,G418筛选转染阳性克隆,PACAP38标准品诱导阳性克隆细胞的胞内cAMP生成,筛选出对PACAP38最为敏感的阳性单克隆细胞株(VPAC2-CHO),运用RT-PCR、Westernblot和免疫荧光法检测VPAC2受体表达情况,利用VPAC2受体特异激动剂通过竞争性结合试验和促进胞内第二信使cAMP生成的活性检测实验证实,VPAC2-CHO特异表达有功能的VPAC2。Scatchard作图分析显示VPAC2-CHO的VPAC2受体密度为(1.1±0.2)pmol/mg膜蛋白,PACAP38与VPAC2的解离常数Kd值为(0.55±0.10)nmol/L。特异表达VPAC2受体细胞系的构建为深入研究该受体理化性质、生物学功能以及筛选、开发VPAC2受体新型特异激动剂和拮抗剂等研究奠定了基础。     

交感神经系统内的递质共存及其相互作用

在外周交感神经系统内;神经递质或神经肽类物质主要存在于大、小囊泡内;递质共存的现象在交感神经内不断得以发现,去甲肾上腺素和乙酰胆碱、神经肽Y、脑啡肽、P物质、血管活性肠肽、生长抑素、神经降压素、降钙素基因相关肽等物质共存的证实,扩大了交感神经递质的调节范围,递质之间网络式的相互调节作用有着重要的生理意义。     

交感神经系统内递质共存及其相互作用

在外周交感神经系统内,神经递质或神经肽类物质主要存在于大、小囊泡内;递质共存的现象在交感神经内不断得以发现．去甲肾上腺素和乙酰胆碱、神经肽Y、脑啡肽、P物质、血管活性肠肽、生长抑素、神经降压素、降钙素基因相关肽等物质共存的证实,扩大了交感神经递质的调节范围,递质之间网络式的相互调节作用有着重要的生理意义。     

肝胆汁分泌的调节

在调节肝胆汁分泌的因素中,除植物性神经系统外,脑-肠肽起着重要作用。其中胰岛素、促胰液素、胆囊收缩素、胃泌素、血管活性肠肽等都是兴奋胆汁分泌的因素;而生长抑素、P物质及TRH是抑制分泌的因素。     

VPAC1激动剂的抗肥胖作用(英文)

VPAC1是垂体腺苷酸环化酶激活多肽（pituitary adenylate cyclase—activating polypeptide，PACAP）和血管活性肠肽（vasoactive intestinal polypeptide，VIP）的共同受体。VPAC1介导PACAP和VIP抑制食欲和抗炎的生物学功能。本研究体外实验表明，VPAC1在分化成熟的3T3-L1脂肪细胞中表达增高，并且VPAC1激动剂（10—1000nmol／L每1×10^6 cells）可诱导脂肪细胞脂解，因此我们预计VPAC1激动剂具有抗肥胖及肥胖综合征的作用。为研究VAPC1激动剂[Lys15，Arg16，Leu27]-VIP（1—7）GRF（8—27）对营养性肥胖及肥胖综合征的干预作用，本研究又设计了两组体内实验：（1）高脂喂养NIH雄性小鼠4周，同时腹腔注射VPAC1激动剂；以注射生理盐水作为对照；（2）高脂喂养NIH雄性小鼠5周，构建肥胖模型后，再腹腔注射VPAC1激动剂4周，同样以注射生理盐水作为对照。采集摄食、体重、体脂、血糖及血脂等指标。结果显示，VPAC1激动剂显著抑制摄食、抑制高脂饮食诱导的体重及体脂（附睾及背部）重量的增长，并有效改善高脂饮食诱导的高血糖及高血脂，提高机体的糖耐受。高剂量（每天50nmol／kg体重）VPAC1激动剂比低剂量（每天5nmol／kg体重）有更显著的抗肥胖作用，提示VPAC1激动剂的抗肥胖作用具有剂量依赖性。以上结果表明，VPAC1激动剂不仅能抑制高脂诱导的肥胖的发展，而且可有效改善肥胖相关疾病：其抗肥胖作用的机制是复杂整合的，值得进一步深入研究。     

降钙素基因相关肽的新近研究进展

降钙素基因相关肽（CGRP）是存在于感觉神经末梢的一种神经肽,是具有代表性的一种活性多肽。实验证明CGRP在身体许多组织器官起着重要的调节作用,特别是对脑具有很强的血管扩张、逆转血管痉挛、改善脑血液循环的作用。对肠道免疫功能也有调节作用,同时介导神经免疫系统的相互调节。     

血管活性肠肽和NF-κB信号通路在骨关节炎中的作用机制

为了考察血管活性肠肽和NF-κB信号通路在骨关节炎中的作用机制,本研究以5周龄SD雄性大鼠为研究材料,通过改良Hulth法建立骨关节炎大鼠模型,然后向大鼠关节内注射血管活性肠肽质粒进行治疗。研究显示,骨关节炎大鼠软骨细胞数量明显减少,细胞弥漫性增加,出现大量细胞簇。在用血管活性肠肽质粒处理后,大鼠膝关节的病理改变显著改善,并且OARSI评分显著降低(p<0.05)。血管活性肠肽质粒处理可显著降低大鼠血清IL-2和TNF-α水平,并升高IL-4水平(p<0.05)。血管活性肠肽质粒处理可显著降低滑膜细胞的增殖能力(p<0.05)。血管活性肠肽质粒处理可显著上调滑膜细胞中的CollagenⅡ和Osteoprotegerin蛋白表达,并下调ADAMTS-5和MMP-13蛋白表达。血管活性肠肽质粒处理可显著下调p-p65表达,并上调p-IκBα表达。综上所述,本研究表明血管活性肠肽可通过抑制滑膜细胞增殖、炎症反应、软骨退变等作用来治疗骨关节炎,其作用机制与抑制NF-κB信号通路的激活有关。     

家兔缺氧后脑中血管活性肠肽含量的变化

本实验采用雄性青紫蓝家兔32只,随机分为急性缺氧组(模拟海拔5000m,2h)、低氧适应组(模拟海拔5000m,2周)和对照组。用放射免疫分析法分别测定了海平和模拟缺氧后大脑皮层、下丘脑和海马三个部位血管活性肠肽含量的变化。测定结果表明,急性缺氧组所测三个部位的血管活性肠肽含量较海平对照均有增高,其中下丘脑的含量自对照的12.1±1.1ng/g增至21.1±2.9ng/g(p<0.05),海马的含量自35.7±2.6ng/g增至45.9±1.7ng(p<0.01)。适应组三个部位的血管活性肠肽含量虽略高于对照,但均无统计学意义。这一结果与前人报道的在相应低氧条件下脑血流变化规律是吻合的。因此我们推测血管活性肠肽在缺氧条件下对脑血流的调节可能起重要作用。     

金黄仓鼠视皮层、上丘和外侧膝状体中的血管活性肠肽(VIP)神经元及其纤维

用程序稍有不同的两种ＰＡＰ法对视觉通路中的三个重要区域视皮层、上６和外侧膝状体中的 血管活性肠肽（ＶＩＰ）进行了定位,．视皮层Ⅱ至Ⅵ层都有ＶＩＰ阳性神经元分布,内域性的阳性神经 纤维遍布整个视皮层。上丘中的ＶＩＰ阳性神经无数量较少,主要分布于上丘的咀部表层,视皮层和 上丘中的ＶＩＰ神经元均为非锥体型的多极和双极神经元。外侧膝状体中未发现有ＶＩＰ阳性神经元 胞体．只有弥散的阳性神经纤维。     

VAPC, an human endogenous inhibitor for hepatitis C virus (HCV) infection, is intrinsically unstructured but forms a "fuzzy complex" with HCV NS5B

Nearly 200 million people are infected by hepatitis C virus (HCV) worldwide. For replicating the HCV genome, the membrane-associated machinery needs to be formed by both HCV non-structural proteins (including NS5B) and human host factors such as VAPB. Recently, the 99-residue VAPC, a splicing variant of VAPB, was demonstrated to inhibit HCV replication via binding to NS5B, thus acting as an endogenous inhibitor of HCV infection. So far, the structure of VAPC remains unknown, and its interaction with NS5B has not been biophysically characterized. In this study, we conducted extensive CD and NMR investigations on VAPC which led to several striking findings: 1) although the N-terminal 70 residues are identical in VAPC and VAPB, they constitute the characteristic β-barrel MSP fold in VAPB, while VAPC is entirely unstructured in solution, only with helical-like conformations weakly populated. 2) VAPC is indeed capable of binding to NS5B, with an average dissociation constant (Kd) of ～20 μM. Intriguingly, VAPC remains dynamic even in the complex, suggesting that the VAPC-NS5B is a "fuzzy complex". 3) NMR mapping revealed that the major binding region for NS5B is located over the C-terminal half of VAPC, which is composed of three discrete clusters, of which only the first contains the region identical in VAPC and VAPB. The second region containing ～12 residues appears to play a key role in binding since mutation of 4 residues within this region leads to almost complete loss of the binding activity. 4) A 14-residue mimetic, VAPC-14 containing the second region, only has a ～3-fold reduction of the affinity. Our study not only provides critical insights into how a human factor mediates the formation of the HCV replication machinery, but also leads to design of VAPC-14 which may be further used to explore the function of VAPC and to develop anti-HCV molecules.     

Colonic vasoactive intestinal polypeptide in ulcerative colitis

Vasoactive intestinal polypeptide (VIP) is a 28 amino acid peptide which is localised in both the central and peripheral nervous system. In the human colon VIP is found in all layers and the highest concentrations have been found in the myenteric plexus. It is known that VIP has various effects on intestinal functions: i) it is a potent stimulant of mucosal water and electrolyte secretion: ii) it is involved in the peristaltic reflex: and iii) plays an inhibitory role on immune cell function. Based on these biological effects it has been hypothesized that the intestinal mucosal immune system and inflammation may be influenced by alterations in the tissue concentrations of VIP. Some authors have demonstrated no changes in the VIP colonic content of patients with ulcerative colitis, whereas others have demonstrated a reduction. Our results, using specific radioimmunoassay, showed that there is a significant decrease of VIP in both rectal and colonic mucosa of patients with ulcerative colitis as compared to controls. The VIP decrease is selective since substance P and calcitonin gene-related peptide were unchanged in the mucosal tissue of ulcerative colitis patients and furthermore the VIP alteration is correlated to the degree of mucosal inflammation. These findings suggest that the reduction of VIP mucosal content, even if it represents a non-specific event, could influence local inflammatory response and the activity of the disease.     

The neuropeptide VIP regulates the expression of osteoclastogenic factors in osteoblasts

Osteoclast formation is controlled by stromal cells/osteoblasts expressing macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL), crucial for osteoclast progenitor cell proliferation, survival and differentiation, and osteoprotegerin (OPG) that inhibits the interaction between RANKL and its receptor RANK. Recent data have strongly indicated that the nervous system plays an important role in bone biology. In the present study, the effects of the neuropeptide vasoactive intestinal peptide (VIP), present in peptidergic skeletal nerve fibers, on the expression of RANKL, OPG, and M-CSF in osteoblasts and stromal cells have been investigated. VIP and pituitary adenylate cyclase-activating polypeptide 38 (PACAP-38), but not secretin, stimulated rankl mRNA expression in mouse calvarial osteoblasts. In contrast, VIP inhibited the mRNA expressions of opg and m-csf, effects shared by PACAP-38, but not by secretin. VIP did not affect rankl, opg, or m-csf mRNA expression in mouse bone marrow stromal cells (BMSCs). The effects by VIP on the mRNA expression of rankl, opg, and m-csf were all potentiated by the cyclic AMP phosphodiesterase inhibitor rolipram. In addition, VIP robustly enhanced the phosphorylation of ERK and the stimulatory effect by VIP on rankl mRNA was inhibited by the MEK1/2 inhibitor PD98059. These observations demonstrate that activation of VPAC(2) receptors in osteoblasts enhances the RANKL/OPG ratio by mechanisms mediated by cyclic AMP and ERK pathways suggesting an important role for VIP in bone remodeling.     

Pituitary adenylate cyclase activating polypeptide regulates the basal production of nitric oxide in PC12 cells

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), two members of the VIP/secretin/glucagon family, modulate neurotransmission via stimulation of protein kinases including cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) in the central and peripheral nervous systems. They are reported to co-exist with nitric oxide synthases (NOSs) and other neuropeptides within the nervous system and peripheral tissues. In the present study, we investigated the neuronal role of these peptides in NO production in PC12 cells. We showed that PACAP decreased NO production in a dose-dependent manner, and the activators of protein kinase A and C also inhibited the NO production in PC12 cells. RT-PCR experiments demonstrated that PC12 cells constitutively express the mRNAs for neuronal NOS and the PACAP-specific (PAC1) receptor, and we concluded that PACAP plays an important role in the regulation of nNOS activity through PAC1 receptor in PC12 cells.     

Influence of renovascular hypertension on the distribution of vasoactive intestinal peptide in the stomach and heart of rats

Arterial hypertension is associated with serious dysfunction of the cardiovascular system and digestive system. Given the relevant role of vasoactive intestinal peptide (VIP) in the regulation of digestion process, control of blood pressure and heart rate as well as cardio- and gastro-protective character of the peptide, it appeared worthwhile to undertake the research aimed at immunohistochemical identification and evaluation of VIP-positive structures in the pylorus and heart of hypertensive rats. Up to now, this issue has not been investigated. The experimental model of hypertension in rats according to Goldblatt (two-kidney one clip model of hypertension) was used in the study. The experimental material (pylorus and heart) was collected in the sixth week of the study. VIP-containing structures were evaluated using immunohistochemical and morphometric methods. The analysis of the results showed a significant increase in the number of immunoreactive VIP structures and in the intensity of immunohistochemical staining in the stomach and in the heart of hypertensive rats. Our findings indicate that VIP is an important regulator of cardiovascular and digestive system in physiological and pathological conditions. However, to better understand the exact role of VIP in hypertension further studies need to be carried out.     

Vasoactive intestinal peptide suppresses ovarian granulosa cell apoptosis in vitro by up-regulating Bcl-2 gene expression

Vasoactive intestinal peptide (VIP) is an endogenous peptide showing a rich profile of biological activities. Within ovaries, VIP directly regulates the ovarian functions, including granulosa cells (GCs) development. In the present study, the effects of VIP on proliferation and apoptosis in goose granulosa cells were demonstrated and its underlying mechanism investigated. A strategy of RNAi-mediated "gene silencing" of Bcl-2 (RV-Bcl-2), over-expression of Bcl-2 (JLV-Bcl-2) synthesis, and exogenous VIP was used to treat goose GCs. The results showed the amounts of Bcl-2 protein were negatively correlated with apoptosis of goose GCs in all experimental groups. Compared with other control groups, apoptosis was decreased in goose GCs following treatment of 100 nM VIP, and the amount of Bcl-2 protein was increased (P < 0.05) increased. However, VIP failed to exert an effect on cell proliferation (P > 0.05). In conclusion, the exogenous VIP plays an important role in inhibiting apoptosis of goose GCs via inducing Bcl-2 gene expression.     

Immunolocalisation of vasoactive intestinal peptide and substance P in the developing gut of Dicentrarchus labrax (L.)

This study was carried out on the sea bass (Dicentrarchus labrax) to follow, during development, the appearance and distribution of substance P (SP) and vasoactive intestinal peptide (VIP), which act on gut motility. The results suggest that SP and VIP play an important role as neuromodulators, influencing the motility of the digestive tract starting from the early stages of gut development, even prior to exotrophic feeding. In the peptidergic nervous system, the appearance of immunoreactivity to SP began at the rectum and followed a distal to proximal gradient, whereas for VIP, it began proximally and progressed along a proximal to distal gradient. The two peptides also appeared in gut epithelial cells. In some regions, all the cells were positive. From this distribution of positive cells, we conclude that these peptides may also have other roles, besides being neurotransmitters in the enteric nervous system and hormones of the gastro-entero-pancreatic system. VIP and SP might have paracrine and/or autocrine activity in the physiological maturation of the gut epithelium, as it has already been hypothesised for other peptides.     

Design of peptide mimetics of HIV-1 gp120 for prevention and therapy of HIV disease.

It has been reported that the C-terminus of the second conserved region (C2) of the envelope glycoprotein gp120, encompassing peptide RSANFTDNAKTIIVQLNESVEIN (NTM), is important for infectivity and neutralization of the human immunodeficiency virus type 1 (HIV-1). It was also demonstrated that human natural anti-vasoactive intestinal peptide (VIP) antibodies reactive with this gp120 region play an important role in control of HIV disease progression. The bioinformatic analysis based on the time-frequency signal processing revealed non-obvious similarities between NTM and VIP. When tested against a battery of sera from 46 AIDS patients, these peptides, in spite of a significant difference in their primary structures, showed a similar reactivity profiles (r = 0.83). Presented results point out that similarity in the periodical pattern of some physicochemical properties in primary structures of peptides plays a significant role in determination of their immunological crossreactivity. Based on these findings, we propose this bioinformatic criterion be used for design of VIP/NTM peptide mimetics for prevention and treatment of HIV disease.