The vanilloid receptor TRPV1: role in cardiovascular and gastrointestinal protection. Eur J Pharmacol. 2010;627:1-7. [PMID: 19879868 DOI: 10.1016/j.ejphar.2009.10.053]

Rutaecarpine attenuates hypoxia-induced right ventricular remodeling in rats

Rutaecarpine has been shown to exhibit wide pharmacological effects in the cardiovascular system via stimulation of calcitonin gene-related peptide (CGRP) release. In the present study, the effect of rutaecarpine on hypoxia-induced right ventricular (RV) remodeling and the underlying mechanisms were evaluated. RV remodeling was induced by hypoxia (10 % O2, 3 weeks) in rats. Rats were treated with rutaecarpine (20 or 40 mg/kg) by intragastric administration. Proliferation of cardiac fibroblasts was induced by TGF-β1 (5 ng/mL) and determined by MTS and EdU incorporation method. Cardiac fibroblasts were treated with exogenous CGRP (10 or 100 nM). The concentrations of CGRP and TGF-β1 in plasma were measured by ELISA. The expression of eIF3a, p27, α-SMA, collagen-I/III, ANP, and BNP were measured by real-time PCR or western blot. Hypoxia induced an increase of right ventricle systolic pressure (RVSP), ration of RV/LV+S, and RV/tibial length in rats, while cardiac hypertrophy, apoptosis, and fibrosis were detected. The expression of ANP, BNP, α-SMA, collagen-I, collagen-III, eIF3a, and TGF-β1 was up-regulated, and the expression of p27 was down-regulated in the right ventricle of hypoxia-treated rats. The plasma concentration of CGRP was decreased and TGF-β1 was increased in hypoxia-treated rats. All of these effects induced by hypoxia were attenuated by rutaecarpine in a dose-dependent manner. In cultured cardiac fibroblasts, TGF-β1 significantly promoted the proliferation and up-regulated the expression of α-SMA and collagen-I/III, while the expression of eIF3a was up-regulated and the expression of p27 was down-regulated. The effects of TGF-β1 were attenuated by CGRP. CGRP8-37, a selective CGRP receptor antagonist, abolished the effects of CGRP. Rutaecarpine attenuates hypoxia-induced RV remodeling via stimulation of CGRP release, and the effects of rutaecarpine involve the eIF3a/p27 pathway.

Mechanisms for the cardiovascular effects of glucagon-like peptide-1

Over the past three decades, at least 10 hormones secreted by the enteroendocrine cells have been discovered, which directly affect the cardiovascular system through their innate receptors expressed in the heart and blood vessels or through a neural mechanism. Glucagon-like peptide-1 (GLP-1), an important incretin, is perhaps best studied of these gut-derived hormones with important cardiovascular effects. In this review, I have discussed the mechanism of GLP-1 release from the enteroendocrine L-cells and its physiological effects on the cardiovascular system. Current evidence suggests that GLP-1 has positive inotropic and chronotropic effects on the heart and may be important in preserving left ventricular structure and function by direct and indirect mechanisms. The direct effects of GLP-1 in the heart may be mediated through GLP-1R expressed in atria as well as arteries and arterioles in the left ventricle and mainly involve in the activation of multiple pro-survival kinases and enhanced energy utilization. There is also good evidence to support the involvement of a second, yet to be identified, GLP-1 receptor. Further, GLP-1(9-36)amide, which was previously thought to be the inactive metabolite of the active GLP-1(7-36)amide, may also have direct cardioprotective effects. GLP-1's action on GLP-1R expressed in the central nervous system, kidney, vasculature and the pancreas may indirectly contribute to its cardioprotective effects.

Capsaicin and Its Role in Chronic Diseases

A significant number of experimental and clinical studies published in peer-reviewed journals have demonstrated promising pharmacological properties of capsaicin in relieving signs and symptoms of non-communicable diseases (chronic diseases). This chapter provides an overview made from basic and clinical research studies of the potential therapeutic effects of capsaicin, loaded in different application forms, such as solution and cream, on chronic diseases (e.g. arthritis, chronic pain, functional gastrointestinal disorders and cancer). In addition to the anti-inflammatory and analgesic properties of capsaicin largely recognized via, mainly, interaction with the TRPV1, the effects of capsaicin on different cell signalling pathways will be further discussed here. The analgesic, anti-inflammatory or apoptotic effects of capsaicin show promising results in arthritis, neuropathic pain, gastrointestinal disorders or cancer, since evidence demonstrates that the oral or local application of capsaicin reduce inflammation and pain in rheumatoid arthritis, promotes gastric protection against ulcer and induces apoptosis of the tumour cells. Sadly, these results have been paralleled by conflicting studies, which indicate that high concentrations of capsaicin are likely to evoke deleterious effects, thus suggesting that capsaicin activates different pathways at different concentrations in both human and rodent tissues. Thus, to establish effective capsaicin doses for chronic conditions, which can be benefited from capsaicin therapeutic effects, is a real challenge that must be pursued.

Lessons from black pepper: piperine and derivatives thereof

INTRODUCTION

Piperine is a simple and pungent alkaloid found in the seeds of black pepper (Piper nigrum). Following its isolation and full characterization, the biological properties of piperine have been extensively studied, and piperine-like derivatives have shown an interesting range of pharmacological activities. In this context, significant advances have been made in the discovery of new chemical entities based on the piperine scaffold endowed with therapeutic potential.

AREAS COVERED

The aim of this review is to provide a thorough inquiry on the therapeutic potential of piperine and related derivatives. It provides an overview of recent developments in patented processes and applications thereof between 2000 and 2015.

EXPERT OPINION

Cumulative evidence shows that piperine is currently paving its way to become a privileged scaffold for the development of bioactive compounds with therapeutic application in multiple human diseases. In particular, piperine derivatives were shown to modulate the activity of several targets related to neurological disorders, including epilepsy, Parkinson's disease, depression and pain related disorders. Moreover, the efflux pump inhibitory ability of piperine and its analogues tackles important drug resistance mechanisms and may improve the clinical efficacy of antibiotic and anticancer drugs. Although the use of piperine as a scaffold for bioactive compounds is still in its early stages, the continuous exploration of this structure may lead to remarkable advances in drug discovery programs.

Discontinued neuropathic pain therapy between 2009-2015

INTRODUCTION

Studies have shown that neuropathic pain remains imprecisely responsive to conventional therapies, therefore posing an ongoing, vexing clinical conundrum for healthcare resource utilization. This manuscript reflects the stark reality of the limited pharmacological choices available to clinicians and is a reflective of an ongoing need for more extensive neuropathic pain clinical research.

AREAS COVERED

The authors review a total of 33 potential drugs for neuropathic pain which were discontinued in the period between 01/01/2009 and 12/31/2014. Eleven drugs were terminated in the first phase of clinical trials; nineteen were discontinued in the second phase, while only three drugs reached the third phase.

EXPERT OPINION

Since only 40-60% of patients obtain partial pain relief from current neuropathic pain treatment options, assuring that they receive new medications for this complex disorder is imperative. However, the authors believe that future studies should not only focus on the discovery of new compounds. Efforts should also be devoted to developing a better understanding of the therapeutic challenges of neuropathic pain, as well as to designing and carrying out clinical trials in collaboration between pharmaceutical companies, physicians and scientists. Furthermore, the authors believe that other outcome measures besides pain intensity, such as functionality and quality of life, should receive more attention.

Consumption of spicy foods and total and cause specific mortality: population based cohort study

OBJECTIVE

To examine the associations between the regular consumption of spicy foods and total and cause specific mortality.

DESIGN

Population based prospective cohort study.

SETTING

China Kadoorie Biobank in which participants from 10 geographically diverse areas across China were enrolled between 2004 and 2008.

PARTICIPANTS

199,293 men and 288,082 women aged 30 to 79 years at baseline after excluding participants with cancer, heart disease, and stroke at baseline.

MAIN EXPOSURE MEASURES

Consumption frequency of spicy foods, self reported once at baseline.

MAIN OUTCOME MEASURES

Total and cause specific mortality.

RESULTS

During 3,500,004 person years of follow-up between 2004 and 2013 (median 7.2 years), a total of 11,820 men and 8404 women died. Absolute mortality rates according to spicy food consumption categories were 6.1, 4.4, 4.3, and 5.8 deaths per 1000 person years for participants who ate spicy foods less than once a week, 1 or 2, 3 to 5, and 6 or 7 days a week, respectively. Spicy food consumption showed highly consistent inverse associations with total mortality among both men and women after adjustment for other known or potential risk factors. In the whole cohort, compared with those who ate spicy foods less than once a week, the adjusted hazard ratios for death were 0.90 (95% confidence interval 0.84 to 0.96), 0.86 (0.80 to 0.92), and 0.86 (0.82 to 0.90) for those who ate spicy food 1 or 2, 3 to 5, and 6 or 7 days a week, respectively. Compared with those who ate spicy foods less than once a week, those who consumed spicy foods 6 or 7 days a week showed a 14% relative risk reduction in total mortality. The inverse association between spicy food consumption and total mortality was stronger in those who did not consume alcohol than those who did (P=0.033 for interaction). Inverse associations were also observed for deaths due to cancer, ischemic heart diseases, and respiratory diseases.

CONCLUSION

In this large prospective study, the habitual consumption of spicy foods was inversely associated with total and certain cause specific mortality, independent of other risk factors of death.

Impaired capsaicin-induced relaxation in diabetic mesenteric arteries

AIMS

To investigate capsaicin-induced vasodilation in the diabetic mesenteric arteries.

METHODS

A diabetic rat model was established by intraperitoneal injection of streptozotocin after a 12-h fast. At 12 weeks post-injection, the third branch of the mesenteric artery was dissected out and prepared for vascular reactivity assessment. Capsaicin, capsazepine, N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME), sodium nitroprusside (SNP), calcitonin gene-related peptide 8-37 (CGRP8-37), calcitonin gene-related peptide (CGRP), and substance P (SP) were added to investigate subsequent alterations in vascular activity. Plasma and physiological salt solution (PSS) levels of CGRP and SP were measured using radioimmunoassay. The expression of transient receptor potential vanilloid 1 (TRPV1) and phospho-eNOS were determined using Western blot analysis, and nitric oxide (NO) production was measured using a fluorescence probe.

RESULTS

The dilation effect of capsaicin was weaker under the diabetic than control conditions. Capsazepine, L-NAME, and CGRP8-37 attenuated capsaicin-induced vasorelaxation significantly in the diabetic vascular rings. Exogenous CGRP elicited dose-dependent vasodilation in the control arteries, whereas the dilation effect was reduced under diabetic conditions. Plasma and PSS CGRP levels were attenuated and mesenteric artery TRPV1 expression was decreased in the diabetic rats. Phospho-eNOS levels were augmented, and NO production increased following the administration of capsaicin.

CONCLUSIONS

Decreased expression of TRPV1 and associated neuropeptide release contributed to the impaired capsaicin-induced vasodilation in diabetic mesenteric arteries. Furthermore, an endothelium-dependent NO-related pathway was involved in capsaicin-induced vasodilation.

Nerve growth factor rescues diabetic mice heart after ischemia/reperfusion injury via up-regulation of the TRPV1 receptor

AIMS

Nerve growth factor (NGF), a member of the neurotrophin family, plays an essential role in diabetic neuropathy and ischemic heart disease. In the present study, we explored the potential role of NGF and the involvement of TRPV1 receptor in isolated diabetic mouse hearts following ischemia/reperfusion (I/R) injury.

METHODS

Adenovirus-mediated NGF gene delivery was performed on diabetic and sham hearts 8weeks after streptozotocin treatment. The sciatic nerve conduction velocity was recorded using a biological signal acquisition system. Forty-eight hours after heart surgery, mice were subjected to I/R injury using a Langendorff system. Several cardiac parameters and the expression of associated molecules were analyzed during the experiment.

RESULTS

The sciatic nerve conduction velocity was reduced in diabetic mice compared with that in control mice. Decreased expression of NGF, TRPV1, and the downstream neurotransmitters CGRP and SP was observed in the diabetic hearts. Adenovirus-mediated NGF overexpression reversed the reduction in TRPV1 and downstream neuropeptides, resulting in improved cardiac recovery post-I/R injury in diabetic hearts. The protective effect of NGF was abolished by CGRP8-37 (a selective CGRP antagonist), while it was preserved by low-dose capsaicin.

CONCLUSIONS

The NGF-induced up-regulation of TRPV1 via the increased synthesis and release of endogenous CGRP leads to improved cardiac performance in I/R-injured diabetic heart.

Capsaicinoids but not their analogue capsinoids lower plasma cholesterol and possess beneficial vascular activity

Capsaicinoids exist in chili peppers, whereas capsinoids are present in some sweet peppers. The present study investigated the effects of capsaicinoids and capsinoids on plasma lipids, relaxation of the aorta, atherosclerotic plaque development, and fecal sterol excretion in hamsters fed a high-cholesterol diet. Five groups of male hamsters were given the control diet or one of the four experimental diets containing 1.3 mmol of capsaicinoids (NL), 2.6 mmol of capsaicinoids (NH), 1.3 mmol of capsinoids (OL), or 2.6 mmol of capsinoids (OH), respectively. Results showed capsaicinoids but not capsinoids could decrease plasma total cholesterol (TC), reduce the formation of atherosclerotic plaque, and relax the aortic artery. This was accompanied by a 28-175% increase in fecal excretion of acidic sterols in hamsters fed the diets containing capsaicinoids. Similarly, capsaicinoids but not capsinoids could decrease the pad weights of epididymal and prerenal adipose tissues. It was concluded that capsaicinoids but not capsinoids could favorably modulate plasma lipids and possess beneficial vascular activity.

Rutaecarpine suppresses atherosclerosis in ApoE-/- mice through upregulating ABCA1 and SR-BI within RCT

ABCA1 and scavenger receptor class B type I (SR-BI)/CD36 and lysosomal integral membrane protein II analogous 1 (CLA-1) are the key transporter and receptor in reverse cholesterol transport (RCT). Increasing the expression level of ABCA1 and SR-BI/CLA-1 is antiatherogenic. The aim of the study was to find novel antiatherosclerotic agents upregulating expression of ABCA1 and SR-BI/CLA-1 from natural compounds. Using the ABCA1p-LUC and CLA-1p-LUC HepG2 cell lines, we found that rutaecarpine (RUT) triggered promoters of ABCA1 and CLA-1 genes. RUT increased ABCA1 and SR-BI/CLA-1 expression in vitro related to liver X receptor alpha and liver X receptor beta. RUT induced cholesterol efflux in RAW264.7 cells. ApoE-deficient (ApoE(-/-)) mice treated with RUT for 8 weeks showed ∼68.43, 70.23, and 85.56% less en face lesions for RUT (L), RUT (M), and RUT (H) groups, respectively, compared with the model group. Mouse macrophage-specific antibody and filipin staining indicated that RUT attenuated macrophages and cholesterol accumulations in atherosclerotic lesions, respectively. Additionally, ABCA1 and SR-BI expression was highly induced by RUT in livers of ApoE(-/-) mice. Meanwhile, RUT treatment significantly increased the fecal (3)H-cholesterol excretion, which demonstrated that RUT could promote RCT in vivo. RUT was identified to be a candidate that protected ApoE(-/-) mice from developing atherosclerosis through preferentially promoting activities of ABCA1 and SR-BI within RCT.

Dihydrocapsaicin down-regulates apoM expression through inhibiting Foxa2 expression and enhancing LXRα expression in HepG2 cells

Background

Apolipoprotein M (apoM), as a novel apolipoprotein which is mainly expressed in liver and kidney tissues, is associated with development and progression of atherosclerosis and diabetes. Our group have recently shown that Dihydrocapsaicin(DHC)can significantly decrease atherosclerotic plaque formation in apoE−/− mice. However, the effect and possible mechanism of DHC on apoM expression remain unclear.

Methods

HepG2 cells were treated with 0 μM, 25 μM, 50 μM and 100 μM DHC for 24 h or were treated with 100 μM DHC for 0, 6, 12, and 24 h, respectively. The mRNA levels and protein levels were measured by real-time quantitative PCR and western blot analysis, respectively.

Results

We found that DHC markedly decreased expression of apoM at both mRNA and protein level in HepG2 cells in a dose-dependent and time-dependent manner. Expression of Foxa2 was decreased while expression of LXRα was increased by DHC treatment in HepG2 cells. In addittion, overexpression of Foxa2 markedly compensated the inhibition effect induced by DHC on apoM expression. LXRα small interfering RNA significantly abolished the inhibition effect which induced by DHC on apoM expression. The liver of C57BL/6 mice treated with DHC had significantly lower expression of apoM. Furthermore, the liver had lower expression of Foxa2 while had higher expression of LXRα.

Conclusions

DHC could down-regulate apoM expression through inhibiting Foxa2 expression and enhancing LXRα expression in HepG2 cells.

Calcitonin gene-related peptide is a key neurotransmitter in the neuro-immune axis

The question of how the neural and immune systems interact in host defense is important, integrating a system that senses the whole body with one that protects. Understanding the mechanisms and routes of control could produce novel and powerful ways of promoting and enhancing normal functions as well as preventing or treating abnormal functions. Fragmentation of biological research into specialities has resulted in some failures in recognizing and understanding interactions across different systems and this is most striking across immunology, hematology, and neuroscience. This reductionist approach does not allow understanding of the in vivo orchestrated response generated through integration of all systems. However, many factors make the understanding of multisystem cross-talk in response to a threat difficult, for instance the nervous and immune systems share communication molecules and receptors for a wide range of physiological signals. But, it is clear that physical, hard-wired connections exist between the two systems, with the key link involving sensory, unmyelinated nerve fibers (c fibers) containing the neuropeptide calcitonin gene-related peptide (CGRP), and modified macrophages, mast cells and other immune and host defense cells in various locations throughout the body. In this review we will therefore focus on the induction of CGRP and its key role in the neuroimmune axis.

TRP modulation by natural compounds

The use of medicinal plants or other naturally derived products to relieve illness can be traced back over several millennia, and these natural products are still extensively used nowadays. Studies on natural products have, over the years, enormously contributed to the development of therapeutic drugs used in modern medicine. By means of the use of these substances as selective agonists, antagonists, enzyme inhibitors or activators, it has been possible to understand the complex function of many relevant targets. For instance, in an attempt to understand how pepper species evoke hot and painful actions, the pungent and active constituent capsaicin (from Capsicum sp.) was isolated in 1846 and the receptor for the biological actions of capsaicin was cloned in 1997, which is now known as TRPV1 (transient receptor potential vanilloid 1). Thus, TRPV1 agonists and antagonists have currently been tested in order to find new drug classes to treat different disorders. Indeed, the transient receptor potential (TRP) proteins are targets for several natural compounds, and antagonists of TRPs have been synthesised based on the knowledge of naturally derived products. In this context, this chapter focuses on naturally derived compounds (from plants and animals) that are reported to be able to modulate TRP channels. To clarify and make the understanding of the modulatory effects of natural compounds on TRPs easier, this chapter is divided into groups according to TRP subfamilies: TRPV (TRP vanilloid), TRPA (TRP ankyrin), TRPM (TRP melastatin), TRPC (TRP canonical) and TRPP (TRP polycystin). A general overview on the naturally derived compounds that modulate TRPs is depicted in Table 1.

Capsaicin receptor as target of calcitonin gene-related peptide in the gut

Calcitonin gene-related peptide (CGRP), a 37 aminoacid-residue peptide, is a marker of afferent fibers in the upper gastrointestinal tract, being almost completely depleted following treatment with the selective neurotoxin capsaicin that targets these fibers via transient receptor potential vanilloid type-1 (TRPV-1). It is widely distributed in the peripheral nervous system of mammals where it is present as alpha isoform, while intrinsic neurons of the enteric nervous systems express predominantly CGRP-beta. Many gastrointestinal functions involve CGRP-containing afferent fibers of the enteric nervous system such as defense against irritants, intestinal nociception, modulation of gastrointestinal motility and secretion, and healing of gastric ulcers. The main effects on stomach homeostasis rely on local vasodilator actions during increased acid-back diffusion. In humans, release of CGRP through the activation of TRPV-1 has been shown to protect from gastric damage induced by several stimuli and to be involved in gastritis. In both dyspepsia and irritable bowel syndrome the repeated stimulation of TRPV-1 induced an improvement in epigastric pain of these patients. The TRPV-1/CGRP pathway might be a novel target for therapeutics in gastric mucosal injury and visceral sensitivity.

Cold stress accentuates pressure overload-induced cardiac hypertrophy and contractile dysfunction: role of TRPV1/AMPK-mediated autophagy

Severe cold exposure and pressure overload are both known to prompt oxidative stress and pathological alterations in the heart although the interplay between the two remains elusive. Transient receptor potential vanilloid 1 (TRPV1) is a nonselective cation channel activated in response to a variety of exogenous and endogenous physical and chemical stimuli including heat and capsaicin. The aim of this study was to examine the impact of cold exposure on pressure overload-induced cardiac pathological changes and the mechanism involved. Adult male C57 mice were subjected to abdominal aortic constriction (AAC) prior to exposure to cold temperature (4 °C) for 4 weeks. Cardiac geometry and function, levels of TRPV1, mitochondrial, and autophagy-associated proteins including AMPK, mTOR, LC3B, and P62 were evaluated. Sustained cold stress triggered cardiac hypertrophy, compromised depressed myocardial contractile capacity including lessened fractional shortening, peak shortening, and maximal velocity of shortening/relengthening, enhanced ROS production, and mitochondrial injury, the effects of which were negated by the TRPV1 antagonist SB366791. Western blot analysis revealed upregulated TRPV1 level and AMPK phosphorylation, enhanced ratio of LC3II/LC3I, and downregulated P62 following cold exposure. Cold exposure significantly augmented AAC-induced changes in TRPV1, phosphorylation of AMPK, LC3 isoform switch, and p62, the effects of which were negated by SB366791. In summary, these data suggest that cold exposure accentuates pressure overload-induced cardiac hypertrophy and contractile defect possibly through a TRPV1 and autophagy-dependent mechanism.

Different TRPV1-mediated brain responses to intragastric infusion of capsaicin and capsiate

Capsaicin and capsiate, which is an analogue of capsaicin, are agonists of capsaicin-binding transient potential vanilloid 1 (TRPV1) receptors. However, their physiological effects are different. Capsaicin induces thermogenesis and nociception, while the different kinetics of capsiate result in thermogenesis without nociception in the oral cavity. In the present study, using functional magnetic resonance imaging, we compared the brain activation after intragastric infusion of non-nociceptive levels of capsaicin and capsiate in wild-type and TRPV1-knockout (KO) mice. Capsaicin activated several brain regions, such as the periaqueductal grey (PAG), thalamic nuclei and hypothalamus, including the medial preoptic area (mPOA) and ventromedial hypothalamus (VMH). Most of these areas were not activated in TRPV1-KO mice. Capsiate activated several regions, including the thalamic nuclei, mPOA and VMH but not PAG in wild-type mice. Most of the activated areas were not activated by intragastric capsiate infusion in TRPV1-KO mice. These results demonstrate that TRPV1 is critical for the induction of activation in the hypothalamus by capsaicin and capsiate, and these distinct brain activations could help to explain the individual physiological reactions of capsaicin and capsiate.

A study to investigate capsaicin-induced pressure response in vagotomized rats

Objectives:

Capsaicin is used to evoke pulmonary C reflexes and produces complex pressure responses along with apnea/tachypnea, and bradycardia. In the present study, the mechanisms involved in capsaicin-induced pressure responses were explored.

Materials and Methods:

Tracheal, jugular venous, and femoral artery cannulations were performed in anesthetized adult rats. Blood pressure, respiratory excursions, and electrocardiogram were recorded. Cardiorespiratory reflex changes evoked by jugular venous injection of capsaicin (10 μg/kg) were recorded in vagotomized and antagonist pretreated animals.

Results:

Capsaicin produced triphasic pressure response exhibiting immediate hypotension, intermediate recovery, and delayed hypotension. Time-matched respiratory changes showed apnea, bradypnea, and tachypnea, respectively. Bradycardia occurred at immediate and intermediate phases. After vagotomy, immediate hypotension was abolished; the intermediate recovery was potentiated as hypertensive response; and the delayed hypotension persisted. In case of respiration, the immediate bradypnea persisted and delayed tachypnea was abolished; while heart rate changes at immediate and intermediate phases were abolished. Antagonists of α₁-adrenoceptor (prazosin or terazosin, 0.5 mg/kg), β-adrenoceptor (propranolol, 1 mg/kg), AT₁ receptor (losartan, 10 mg/kg) and Ca²⁺ channel (diltiazem, 1 mg/kg) failed to block the capsaicin-induced intermediate hypertensive response in vagotomized animals.

Conclusions:

These observations implicate the existence of mechanisms other than adrenergic, angiotensinergic, or Ca²⁺ channel-dependent mechanisms for mediating the capsaicin-induced intermediate hypertensive response in vagotomized animals.

Dihydrocapsaicin Attenuates Plaque Formation through a PPARγ/LXRα Pathway in apoE(-/-) Mice Fed a High-Fat/High-Cholesterol Diet

Aims

Atherosclerosis is a chronic inflammatory disease and represents the major cause of cardiovascular morbidity and mortality. There is evidence that dihydrocapsaicin (DHC) can exert multiple pharmacological and physiological effects. Here, we explored the effect of DHC in atherosclerotic plaque progression in apoE^−/− mice fed a high-fat/high-cholesterol diet.

Methods and Results

apoE^−/− mice were randomly divided into two groups and fed a high-fat/high-cholesterol diet with or without DHC for 12 weeks. We demonstrated that cellular cholesterol content was significantly decreased while apoA1-mediated cholesterol efflux was significantly increased following treatment with DHC in THP-1 macrophage-derived foam cells. We also observed that plasma levels of TG, LDL-C, VLDL-C, IL-1β, IL-6, TNF-α and CRP were markedly decreased while plasma levels of apoA1 and HDL-C were significantly increased, and consistent with this, atherosclerotic lesion development was significantly inhibited by DHC treatment of apoE^−/− mice fed a high-fat/high-cholesterol diet. Moreover, treatment with both LXRα siRNA and PPARγ siRNA made the up-regulation of DHC on ABCA1, ABCG1, ABCG5, SR-B1, NPC1, CD36, LDLR, HMGCR, apoA1 and apoE expression notably abolished while made the down-regulation of DHC on SRA1 expression markedly compensated. And treatment with PPARγ siRNA made the DHC-induced up-regulation of LXRα expression notably abolished while treatment with LXRα siRNA had no effect on DHC-induced PPARγ expression.

Conclusion

These observations provide direct evidence that DHC can significantly decrease atherosclerotic plaque formation involving in a PPARγ/LXRα pathway and thus DHC may represent a promising candidate for a therapeutic agent for the treatment or prevention of atherosclerosis.

Pharmacokinetic characteristics of capsaicin-loaded nanoemulsions fabricated with alginate and chitosan

Nanotechnologies are being employed to enhance the stability and oral bioavailability of lipophilic substances, such as capsaicin. This study aimed to examine the pharmacokinetic properties of the formulated capsaicin-loaded nanoemulsions. A pharmacokinetic study was carried out using double-layer nanoemulsions fabricated with alginate and chitosan polymers and triple-layer nanoemulsions fabricated with chitosan/alginate polymers. Capsaicin nanoemulsions and capsaicin control (oleoresin capsicum) were administered to the rat at a dose of 10 mg/kg. A statistically significant difference was found in the area under the curve from time zero to time infinity (AUCinf) among formulations (p < 0.01). In comparison to the control group, the relative bioavailability of formulated nanoemulsions was up to 131.7. The AUCinf increased in a nano-size-dependent manner; as nano size decreased, AUCinf increased. IN comparison to the double-layer nanoemulsions, the triple-layer nanoemulsion showed a significantly increased volume of distribution, resulting in the increased clearance and decreased AUCinf. It was concluded that the formulated nanoemulsions could significantly enhance the bioavailabilty of capsaicin.

Stimulation of calcitonin gene-related peptide release through targeting capsaicin receptor: a potential strategy for gastric mucosal protection

Calcitonin gene-related peptide (CGRP) is a predominant neurotransmitter from capsaicin-sensitive sensory nerves, which are widely distributed in the gastrointestinal system. These sensory nerves are reported to be involved in the protection of gastric mucosa against damage by various stimuli, and CGRP is a potential mediator in this process. In addition to increase in gastric mucosal blood flow, the beneficial effects of CGRP on gastric mucosa include inhibition of gastric acid secretion, prevention of cellular apoptosis and oxidative injury. The synthesis and release of CGRP is regulated by the capsaicin receptor which is known as transient receptor potential vanilloid subfamily member 1 (TRPV1) and the agonists of TRPV1 have the potential for gastric mucosal protection. So far, multiple TRPV1 agonists, including capsaicin, capsiate, anandamide and rutaecarpine are reported to exert beneficial effects on gastric mucosal injury induced by various stimuli. Therefore, the TRPV1/CGRP pathway represents a novel target for therapeutic intervention in human gastric mucosal injury.

Pharmacological actions of multi-target-directed evodiamine

Evodiamine, a naturally occurring indole alkaloid, is one of the main bioactive ingredients of Evodiae fructus. With respect to the pharmacological actions of evodiamine, more attention has been paid to beneficial effects in insults involving cancer, obesity, nociception, inflammation, cardiovascular diseases, Alzheimer's disease, infectious diseases and themoregulative effects. evodiamine has evolved a superior ability to bind various proteins, so we also argue that it is good starting point for multi-target drugs. This review is primarily addressed to the description of the recent advances in the biological activity studies of evodiamine, with a focus on pharmacological mechanism. The present review also includes the pharmacokinetics and the detailed exploration of target-binding properties of evodiamine in an attempt to provide a direction for further multi-target drug design.

Spices: the savory and beneficial science of pungency

Spicy food does not only provide an important hedonic input in daily life, but has also been anedoctically associated to beneficial effects on our health. In this context, the discovery of chemesthetic trigeminal receptors and their spicy ligands has provided the mechanistic basis and the pharmacological means to investigate this enticing possibility. This review discusses in molecular terms the connection between the neurophysiology of pungent spices and the "systemic" effects associated to their trigeminality. It commences with a cultural and historical overview on the Western fascination for spices, and, after analysing in detail the mechanisms underlying the trigeminality of food, the main dietary players from the transient receptor potential (TRP) family of cation channels are introduced, also discussing the "alien" distribution of taste receptors outside the oro-pharingeal cavity. The modulation of TRPV1 and TRPA1 by spices is next described, discussing how spicy sensations can be turned into hedonic pungency, and analyzing the mechanistic bases for the health benefits that have been associated to the consumption of spices. These include, in addition to a beneficial modulation of gastro-intestinal and cardio-vascular function, slimming, the optimization of skeletal muscle performance, the reduction of chronic inflammation, and the prevention of metabolic syndrome and diabetes. We conclude by reviewing the role of electrophilic spice constituents on cancer prevention in the light of their action on pro-inflammatory and pro-cancerogenic nuclear factors like NFκB, and on their interaction with the electrophile sensor protein Keap1 and the ensuing Nrf2-mediated transcriptional activity. Spicy compounds have a complex polypharmacology, and just like any other bioactive agent, show a balance of beneficial and bad actions. However, at least for moderate consumption, the balance seems definitely in favour of the positive side, suggesting that a spicy diet, a caveman-era technology, could be seriously considered in addition to caloric control and exercise as a measurement to prevent and control many chronic diseases associate to malnutrition from a Western diet.

Acute myocardial ischemia enhances the vanilloid TRPV1 and serotonin 5-HT3 receptor-mediated Bezold-Jarisch reflex in rats

The Bezold-Jarisch reflex is characterized by a sudden bradycardia associated with hypotension induced by the activation of the vanilloid TRPV1 and serotonin 5-HT(3) receptors. This reflex is associated with several health conditions, including myocardial infarction. The aim of the present study was to elucidate the influence of acute experimental myocardial ischemia on the reflex bradycardia induced by anandamide and phenylbiguanide, agonists of the TRPV1 and 5-HT(3) receptors, respectively. In urethane-anesthetized rats, the rapid iv injection of anandamide (0.6 μmol/kg) or phenylbiguanide (0.03 μmol/kg) decreased heart rate (HR) by about 7-10% of the basal values. Myocardial ischemia (MI) was induced by ligation of the left anterior coronary artery. The agonists were injected 5 min before MI (S(1)) and 10, 20 and 30 min thereafter (S(2)-S(4)). MI potentiated the anandamide-induced reflex bradycardia by approximately 105% at S(2) and 70% at S(3) but had no effect at S(4). This amplificatory effect of MI was virtually abolished by the TRPV1 receptor antagonist capsazepine (1 μmol/kg) and was not modified by the cannabinoid CB(1) receptor antagonist rimonabant (0.1 μmol/kg). MI also amplified the reflex bradycardia elicited by phenylbiguanide by approximately 110, 60 and 90% (S(2), S(3) and S(4), respectively), and this effect was sensitive to the 5-HT(3) receptor antagonist ondansetron (3 μmol/kg). In conclusion, our results suggest that acute myocardial ischemia augments the Bezold-Jarisch reflex induced via activation of TRPV1 and 5-HT(3) receptors located on sensory vagal nerves in the heart.

Binding mode pediction of evodiamine within vanilloid receptor TRPV1

Accurate assessment of the potential binding mode of drugs is crucial to computer-aided drug design paradigms. It has been reported that evodiamine acts as an agonist of the vanilloid receptor Transient receptor potential vanilloid-1 (TRPV1). However, the precise interaction between evodiamine and TRPV1 was still not fully understood. In this perspective, the homology models of TRPV1 were generated using the crystal structure of the voltage-dependent shaker family K⁺ channel as a template. We then performed docking and molecular dynamics simulation to gain a better understanding of the probable binding modes of evodiamine within the TRPV1 binding pocket. There are no significant interspecies differences in evodiamine binding in rat, human and rabbit TRPV1 models. Pharmacophore modeling further provided confidence for the validity of the docking studies. This study is the first to shed light on the structural determinants required for the interaction between TRPV1 and evodiamine, and gives new suggestions for the rational design of novel TRPV1 ligands.

Antioxidant activity of capsaicinoid in canola oil

Interest in replacing synthetic antioxidants, namely, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), with natural antioxidants is increasing. The present study examined the antioxidant activity of capsaicinoid from chili pepper in heated canola oil. The oxidation was conducted at 60, 90, 120, and 180 °C by monitoring oxygen consumption and the decrease in linoleic acid and α-linolenic acid in canola oil. At 60 °C, capsaicinoid was more effective against oxidation of canola oil compared with BHT. At higher temperatures of 90, 120, and 180 °C, capsaicinoid possessed an antioxidant activity similar to or slightly weaker that that of BHT. It was found that capsaicinoid prevented canola oil from oxidation in a dose-dependent manner. To study the structure-antioxidant relationship, it was found that the trimethylsiloxy (TMS) derivatives of capsaicinoid did not exhibit any antioxidant activity, suggesting the hydroxyl moiety was the functional group responsible for the antioxidant activity of capsaicinoid. It was concluded that capsaicinoid had the potential to be further explored as a natural antioxidant in foods, particularly spicy foods.

Substance P release in response to cardiac ischemia from rat thoracic spinal dorsal horn is mediated by TRPV1

Spinal cord stimulation (SCS) inhibits substance P (SP) release and decreases the expression of the transient receptor potential vanilloid 1 (TRPV1) in the spinal cord at thoracic 4 (T4) during cardiac ischemia in rat models (Ding et al., 2007). We hypothesized that activation of TRPV1 in the T4 spinal cord segment by intermittent occlusion of the left anterior descending coronary artery (CoAO) mediates spinal cord SP release. Experiments were conducted in urethane-anesthetized Sprague-Dawley male rats using SP antibody-coated microprobes to measure SP release at the central terminal endings of cardiac ischemic-sensitive afferent neurons (CISAN) in the spinal T4 dorsal horns. Vehicle, capsaicin (CAP; TRPV1 agonist) and capsazepine (CZP; TRPV1 antagonist) were injected into the left T4 prior to stimulation of CISAN by intermittent CoAO (with or without upper cervical SCS). CAP induced endogenous SP release from laminae I and II in the T4 spinal cord above baseline. Conversely, CZP injections significantly inhibited SP release from laminae I-VII in the T4 spinal cord segment below baseline. CZP also attenuated CoAO-induced SP release, while T4 injections of CZP with SCS completely restored SP release to basal levels during CoAO activation. CAP increased the number of c-Fos (a marker for CISAN activation) positive T4 dorsal horn neurons compared to sham-operated animals, while CZP (alone or during CoAO and SCS+CoAO) significantly reduced the number of c-Fos positive neurons. These results suggest that spinal release of the putative nociceptive transmitter SP occurs, at least in part, via a TRPV1 mechanism.

Target molecules of food phytochemicals: food science bound for the next dimension

Phytochemicals are generally defined as secondary metabolites in plants that play crucial roles in their adaptation to a variety of environmental stressors. There is a great body of compelling evidence showing that these metabolites have pronounced potentials for regulating and modulating human health and disease onset, as shown by both experimental and epidemiological approaches. Concurrently, enormous efforts have been made to elucidate the mechanism of actions underlying their biological and physiological functions. For example, the pioneering work of Tachibana et al. uncovered the receptor for (-)-epigallocatechin-3-gallate (EGCg) as the 67 kDa laminin receptor, which was shown to partially mediate the functions of EGCg, such as anti-inflammatory, anti-allergic, and anti-proliferative activities. Thereafter, several protein kinases were identified as binding proteins of flavonoids, including myricetin, quercetin, and kaempferol. Isothiocyanates, sulfur-containing phytochemicals present in cruciferous plants, are well known to target Keap1 for activating the transcription factor Nrf2 for inducing self-defensive and anti-oxidative gene expression. In addition, we recently identified CD36 as a cell surface receptor for ursolic acid, a triterpenoid ubiquitously occurring in plants. Importantly, the above mentioned target proteins are indispensable for phytochemicals to exhibit, at least in part, their bioactivities. Nevertheless, it is reasonable to assume that some of the activities and potential toxicities of metabolites are exerted via their interactions with unidentified, off-target proteins. This notion may be supported by the fact that even rationally designed drugs occasionally display off-target effects and induce unexpected outcomes, including toxicity. Here we update the current status and future directions of research related to target molecules of food phytochemicals.

Sympathetic overdrive in obesity involves purinergic hyperactivity in the resistance vasculature

While a close correlation exists in obese humans between sympathetic, adrenergic hyperactivity and structural and functional organ damage, a role for the co-transmitter, ATP, in vascular function remains unexplored. We therefore studied sympathetic nerve-mediated responses of pressurised small mesenteric arteries from control and obese rats. Diet-induced obesity significantly increased the amplitude of vasoconstriction to transmural nerve stimulation (1-10 Hz; P <0.05). At 1 and 5 Hz, both adrenergic and purinergic responses were significantly augmented, while only the purinergic component was increased at 10 Hz (P <0.05). Nerve stimulation at 1 Hz evoked contractions and underlying excitatory junction potentials (EJPs), which were both significantly increased in amplitude during obesity (P <0.05) and abolished by αβ-methylene ATP (1 μM; desensitises purinergic receptors). The rise time and rate of decay of these EJPs were significant decreased (P <0.05), without change in resting membrane potential. Amplitude and frequency of spontaneous EJPs and the density of perivascular sympathetic nerves were also significantly increased (P <0.05). Inhibition of sensory neurotransmitter release (capsaicin; 10 μM) significantly increased the amplitude of nerve-mediated contraction (P <0.05), with a greater effect in control than obese animals, although the density of sensory nerves was unaffected by obesity. We demonstrate that sympathetic nerve-mediated vasoconstriction is enhanced by diet-induced obesity due to upregulation of purinergic, in addition to adrenergic, neurotransmission. Changes result from increased perivascular sympathetic innervation and release of ATP. We conclude that augmented sympathetic control of vasoconstriction induced by obesity could contribute directly to hypertension and global organ damage. A decrease in sensitivity to sensory vasodilatory neurotransmitters may also affect these processes.

Calcitonin gene-related peptide (CGRP) and its role in hypertension

Hypertension is still presently the number one "silent killer" in the Western World, and a major risk factor for the development of secondary diseases contributing to cardiovascular disease (CVD). However, despite a broad range of therapies, the mechanisms involved in the onset of hypertension remains unclear, therefore there is a real need to investigate the mechanisms involved. Calcitonin gene-related peptide (CGRP) is the most potent microvascular vasodilator known to date. Widely expressed in the nervous system, this peptide is considered to play a positive role in wound healing and protects against ischaemic and other traumas. However, whilst the protective mechanisms are not well understood, evidence indicates that these mechanisms become important in vascular-related stress. This review provides evidence that CGRP is both a potent vasodilator and hypotensive agent. However studies to date suggest that CGRP does not contribute to the physiological regulation of blood pressure. By comparing results from a range of human and animal studies, findings broadly suggest an association between CGRP and the pathophysiology of hypertension in terms of protective mechanisms, with possibly the RAMP1 component of the CGRP receptor playing a key role in the brain stem, in addition to peripheral receptors. The studies of agents that release CGRP agonists are at an early stage, with analogues for human use currently under development. However, at this stage, further research is required to establish the mechanisms by which CGRP is protective in the onset of hypertension, if novel and therapeutic modes of treatment are to be developed.

Reversal of isoprenaline-induced cardiac remodeling by rutaecarpine via stimulation of calcitonin gene-related peptide production

Dysfunction of capsaicin-sensitive sensory nerves is involved in cardiac remodeling, and rutaecarpine has been shown to exert a beneficial effect on cardiac function through activating the sensory nerves. This study was conducted to explore the potential inhibitory effect of rutaecarpine on cardiac remodeling and the underlying mechanisms. A rat cardiac remodeling model was established by injection of isoprenaline (5 mg/kg per day, s.c.) for 10 days. Rutaecarpine (10 or 40 mg/kg, i.g.) was coadministrated with isoprenaline to evaluate the effect of rutaecarpine on cardiac remodeling. After echocardiographic analysis was performed, blood samples were collected to quantify calcitonin gene-related peptide (CGRP), dorsal root ganglia were isolated for examining CGRP mRNA expression, and the hearts were weighed and saved for evaluating the parameters related to apoptosis and hypertrophy. Isoprenaline significantly increased the ratio of left ventricle weight to body weight, the cross-sectional area of cardiomyocytes, cardiac apoptosis, and collagen deposition concomitantly with decreased CGRP production, which were reversed by rutaecarpine treatment. The beneficial effects of rutaecarpine were attenuated by pretreatment with capsaicin, which selectively depleted CGRP. These results suggest that rutaecarpine was able to reverse isoprenaline-induced cardiac remodeling through stimulating CGRP production.

Unusual pungency from extra-virgin olive oil is attributable to restricted spatial expression of the receptor of oleocanthal

Oleocanthal, a major phenolic compound in extra-virgin olive oil with antiinflammatory properties, elicits an unusual oral pungency sensed almost exclusively in the throat. This contrasts with most other common oral irritants, such as cinnamaldehyde, capsaicin, and alcohol, which irritate mucus membranes throughout the oral cavity. Here, we show that this rare irritation pattern is a consequence of both the specificity of oleocanthal for a single sensory receptor and the anatomical restriction of this sensory receptor to the pharynx, within the oral cavity. We demonstrate, in vitro, that oleocanthal selectively activates the hTRPA1 channel in HEK 293 cells and that its ability to excite the trigeminal nervous system in rodents requires a functional TRPA1. Moreover, we similarly demonstrate that the over-the-counter analgesic, ibuprofen, which elicits the same restricted pharyngeal irritation as oleocanthal, also specifically excites rodent sensory neurons via TRPA1. Using human sensory psychophysical studies and immunohistochemical TRPA1 analyses of human oral and nasal tissues, we observe an overlap of the anatomical distribution of TRPA1 and the regions irritated by oleocanthal in humans. These results suggest that a TRPA1 (ANKTM1) gene product mediates the tissue sensitivity to oleocanthal within the oral cavity. Furthermore, we demonstrate that, despite the fact that oleocanthal possesses the classic electrophilic reactivity of many TRPA1 agonists, it does not use the previously identified activation mechanism via covalent cysteine modification. These findings provide an anatomical and molecular explanation for a distinct oral sensation that is elicited by oleocanthal and ibuprofen and that is commonly experienced around the world when consuming many extra-virgin olive oils.

Anti-inflammatory and anti-infectious effects of Evodia rutaecarpa (Wuzhuyu) and its major bioactive components

This article reviews the anti-inflammatory relative and anti-infectious effects of Evodia rutaecarpa and its major bioactive components and the involvement of the nitric oxide synthases, cyclooxygenase, NADPH oxidase, nuclear factor kappa B, hypoxia-inducible factor 1 alpha, reactive oxygen species, prostaglandins, tumor necrosis factor, LIGHT, amyloid protein and orexigenic neuropeptides. Their potential applications for the treatment of endotoxaemia, obesity, diabetes, Alzheimer's disease and their uses as cardiovascular and gastrointestinal protective agents, analgesics, anti-oxidant, anti-atherosclerosis agents, dermatological agents and anti-infectious agents are highlighted. Stimulation of calcitonin gene-related peptide release may partially explain the analgesic, cardiovascular and gastrointestinal protective, anti-obese activities of Evodia rutaecarpa and its major bioactive components.

Recent advances in the study on capsaicinoids and capsinoids

Chili peppers are the major source of nature capsaicinoids, which consist of capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin, etc. Capsaicinoids are found to exert multiple pharmacological and physiological effects including the activities of analgesia, anticancer, anti-inflammation, antioxidant and anti-obesity. Therefore, capsaicinoids may have the potential value in clinic for pain relief, cancer prevention and weight loss. In addition, capsaicinoids also display the benefits on cardiovascular and gastrointestinal system. It has been shown that capsaicinoids are potential agonists of capsaicin receptor or transient receptor potential vanilloid subfamily member 1 (TRPV1). They could exert the effects not only through the receptor-dependent pathway but also through the receptor-independent one. CH-19 Sweet peppers are the source of nature capsinoids, which share similar structure with capsaicinoids and consist of capsiate, dihydrocapsiate, and nordihydrocapsiate, etc, Comparing with capsaicinoids, capsinoids are less pungent and easily broken down in the normal aqueous conditions. So far, it has been found that capsinoids possess the biological properties of antitumor, antioxidant and anti-obesity. Since capsinoids are less toxic than capsaicinoids, therefore, capsinoids may have the advantages over capsaicinoids in clinical applications such as cancer prevention and weight loss.

The pathogenesis of cystinosis: mechanisms beyond cystine accumulation

Renal proximal tubules are highly sensitive to ischemic and toxic insults and are affected in diverse genetic disorders, of which nephropathic cystinosis is the most common. The disease is caused by mutations in the CTNS gene, encoding the lysosomal cystine transporter cystinosin, and is characterized by accumulation of cystine in the lysosomes throughout the body. In the majority of the patients, this leads to generalized proximal tubular dysfunction (also called DeToni-Debré-Fanconi syndrome) in the first year and progressive renal failure during the first decade. Extrarenal organs are affected by cystinosis as well, with clinical symptoms manifesting mostly after 10 yr of age. The cystine-depleting agent cysteamine significantly improves life expectancy of patients with cystinosis, but offers no cure, pointing to the complexity of the disease mechanism. In this review, current knowledge on the pathogenesis of cystinosis is described and placed in perspective of future research.