A possible role of nitric oxide formation in the vasodilatation of rabbit ear artery induced by a topically applied Capsaicin analogue

Ultrathin chalcogenide nanosheets for photoacoustic imaging-guided synergistic photothermal/gas therapy

Previous preclinical and clinical studies have shown that using only a single therapy makes it difficult to completely eradicate tumors and restrain cancer metastasis. To overcome this challenge, multi-modal synergistic treatments have attracted considerable attention. Herein, an ultrathin Cu-loaded CoCuFe-selenide (CCFS) was prepared by a facile topotactic transformation from CoCuFe layered double hydroxide (LDH) nanosheets (NSs), followed by surface modification with polyvinyl pyrrolidone (PVP) and l-arginine (L-Arg). The resultant CCFS-PVP-L-Arg (CPA) system shows excellent synergetic photothermal and gas therapy (PTT/GT). The CCFS NSs have strong LSPR absorbance characteristic, with enhanced light absorption in the near-infrared (NIR) region. This endows the CPA nanocomposite with an outstanding photothermal conversion efficiency of 72.0% (pH 7.4) and 81.0% (pH 5.4), among the highest reported for 2D chalcogenide nanomaterials. In addition, NO release from CPA is triggered by decomposition of L-Arg in the H₂O₂-rich and acidic tumor microenvironment, permitting localized NO gas therapy in the tumor site. In vitro experiments revealed 91.8% apoptosis of HepG2 cells, and in vivo studies showed complete tumor elimination upon treatment with the CPA nanocomposite under NIR irradiation. To the best of our knowledge, this is the first report of combined defect-induced high-efficiency PTT with H₂O₂ and pH targeted GT.

The effect of 4-week chilli supplementation on metabolic and arterial function in humans

OBJECTIVE

To investigate the effects of regular chilli ingestion on some indicators of metabolic and vascular function.

DESIGN

A randomized cross-over dietary intervention study.

SETTING

Launceston, Australia.

SUBJECTS

Healthy free-living individuals.

INTERVENTION

Thirty-six participants (22 women and 14 men), aged 46+/-12 (mean+/-s.d.) years; BMI 26.4+/-4.8 kg/m(2), consumed 30 g/day of a chilli blend (55% cayenne chilli) with their normal diet (chilli diet), and a bland diet (chilli-free) for 4 weeks each. Metabolic and vascular parameters, including plasma glucose, serum lipids and lipoproteins, insulin, basal metabolic rate, blood pressure, heart rate, augmentation index (AIx; an indicator of arterial stiffness), and subendocardial-viability ratio (SEVR; a measure of myocardial perfusion), were measured at the end of each diet. In a sub-study, during week 3 of each dietary period, the vascular responses of 15 subjects to glyceryl-trinitrate (GTN) and salbutamol were also studied.

RESULTS

For the whole group, there were no significant differences between any of the measured parameters when compared at the end of the two dietary periods. When analysed separately, men had a lower resting heart rate (P=0.02) and higher SEVR (P=0.05) at the end of the chilli diet than the bland diet. In the sub-study, baseline AIx on the chilli diet was lower (P<0.001) than on the bland diet, but there was no difference in the effects of GTN and salbutamol between the two diets.

CONCLUSION

Four weeks of regular chilli consumption has no obvious beneficial or harmful effects on metabolic parameters but may reduce resting heart rate and increase effective myocardial perfusion pressure time in men.

The vanilloid receptor as a putative target of diverse chemicals in multiple chemical sensitivity

The vanilloid receptor (TRPV1 or VR1), widely distributed in the central and peripheral nervous system, is activated by a broad range of chemicals similar to those implicated in Multiple Chemical Sensitivity (MCS) Syndrome. The vanilloid receptor is reportedly hyperresponsive in MCS and can increase nitric oxide levels and stimulate N-methyl-D-aspartate (NMDA) receptor activity, both of which are important features in the previously proposed central role of nitric oxide and NMDA receptors in MCS. Vanilloid receptor activity is markedly altered by multiple mechanisms, possibly providing an explanation for the increased activity in MCS and symptom masking by previous chemical exposure. Activation of this receptor by certain mycotoxins may account for some cases of sick building syndrome, a frequent precursor of MCS. Twelve types of evidence implicate the vanilloid receptor as the major target of chemicals, including volatile organic solvents (but not pesticides) in MCS.

Anandamide elicits an acute release of nitric oxide through endothelial TRPV1 receptor activation in the rat arterial mesenteric bed

In the isolated rat mesenteric bed, the 1 min perfusion with 100 nm anandamide, a concentration that did not evoke vasorelaxation, elicited an acute release of 165.1 +/- 9.2 pmol nitric oxide (NO) that was paralleled by a 2-fold increase in cGMP tissue levels. The rise in NO released was mimicked by either (R)-(+)-methanandamide or the vanilloid receptor agonists resiniferatoxin and (E)-capsaicin but not by its inactive cis-isomer (Z)-capsaicin. The NO release elicited by either anandamide or capsaicin was reduced by the TRPV1 receptor antagonists 5'-iodoresiniferatoxin, SB 366791 and capsazepine as well as by the cannabinoid CB(1) receptor antagonists SR 141716A or AM251. The outflow of NO elicited by anandamide and capsaicin was also reduced by endothelium removal or NO synthase inhibition, suggesting the specific participation of endothelial TRPV1 receptors, rather than the novel endothelial TRPV4 receptors. Consistently, RT-PCR showed the expression of the mRNA coding for the rat TRPV1 receptor in the endothelial cell layer, in addition to its expression in sensory nerves. The participation of sensory nerves on the release of NO was precluded on the basis that neonatal denervation of the myenteric plexus sensory nerves did not modify the pattern of NO release induced by anandamide and capsaicin. We propose that low concentrations of anandamide, devoid of vasorelaxing effects, elicit an acute release of NO mediated predominantly by the activation of endothelial TRPV1 receptors whose physiological significance remains elusive.

Improved dorsal random-pattern skin flap survival in rats with a topically applied combination of nonivamide and nicoboxil

The effects of a topically applied combination of nonivamide and nicoboxil in improving skin perfusion and preventing distal flap necrosis were tested in a random-pattern dorsal skin flap model. Forty male Wistar rats were randomized into two groups (n = 20), and a standardized dorsal random-pattern skin flap was raised on each rat. Animals in the experimental group were treated with the topically applied drug combination four times per day for 6 days, whereas in the control group only a placebo ointment was applied each time. Skin flap viability was evaluated on day 7, and the extent of skin flap necrosis was compared between the two groups. The topically applied combination of nonivamide and nicoboxil resulted in a statistically significant decrease in skin flap necrosis, compared with the control group (mean percentage of skin flap necrosis in the nonivamide/nicoboxil-treated group, 22.6 +/- 6.0 percent; control group, 36.8 +/- 4.3 percent; p< 0.05). The topical combination of nonivamide and nicoboxil was effective in reducing ischemic necrosis in failing random-pattern skin flaps in this rat model. The results of this study suggest that such a topical drug application might have significant effects in the reduction of ischemic necrosis in the distal parts of skin flaps, and this treatment might also have applications as prophylactic therapy for risky skin flaps.

Capsazepine, a vanilloid receptor antagonist, inhibits the expression of inducible nitric oxide synthase gene in lipopolysaccharide-stimulated RAW264.7 macrophages through the inactivation of nuclear transcription factor-kappa B

High amounts of nitric oxide (NO) production following the induction of inducible NO synthase (iNOS) gene expression has been implicated in the pathogenesis of inflammatory diseases. Capsaicin, a vanilloid receptor agonist, is known to have an inhibitory effect on NO production in macrophages. In the present study, we have found that capsazepine (CAPZ), a vanilloid receptor antagonist, also inhibited NO and iNOS protein syntheses induced by lipopolysaccharide in RAW264.7 macrophages via the suppression of iNOS mRNA. The mechanistic studies showed that CAPZ inhibited the expression of iNOS mRNA through the inactivation of nuclear transcription factor-kappa B (NF-kappa B). Thus, capsazepine may be a useful candidate for the development of a drug to treat inflammatory diseases related to iNOS gene overexpression.

Importance of endogenous nitric oxide synthase in the rat hypothalamus and amygdala in mediating the response to capsaicin

Although capsaicin has been shown to activate certain neuronal groups in the hypothalamus and amygdala, the neurotransmitters involved and the exact mechanism of action are not clearly understood at present. The aim of this study was to examine the hypothesis that the effect of capsaicin in the rat hypothalamus and amygdala primarily involves direct activation of the endogenous nitric oxide synthase (NOS) neurons responsible for the synthesis of nitric oxide (NO). Subcutaneous capsaicin injection in male rats, compared with vehicle, caused a significant increase in Fos expression in the paraventricular nucleus (PVN), supraoptic nucleus (SON), and medial and cortical amygdala. The expression of nicotinamide adenine dinucleotide phosphate diaphorase, a histochemical marker for NOS, was also increased in these brain areas in addition to the periventricular and lateral hypothalamic area and central amygdaloid nucleus. Also, capsaicin significantly increased the expression of neuronal NOS messenger RNA and protein in the PVN, SON, and medial amygdala as demonstrated by in situ hybridization and immunohistochemistry, respectively. A higher proportion of the NOS neurons in the PVN, periventricular region, SON and amygdala showed Fos expression in response to capsaicin than vehicle injection. There was little, if any, Fos activation in the NOS-positive neurons in the lateral hypothalamic area. The capsaicin-induced activation of the hypothalamic PVN and SON neurons and the medial amygdaloid nucleus was attenuated in the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) -pretreated animals in comparison with the inactive enantiomer D-NAME. These observations indicate that activation of the endogenous NOS system and production of NO constitute a major pathway through which capsaicin exerts its effect within the hypothalamus and amygdala.

Capsaicin-evoked release of immunoreactive calcitonin gene-related peptide from the spinal cord is mediated by nitric oxide but not by cyclic GMP

Recent data support a role for nitric oxide (NO) in pain processing at the level of the spinal cord, possibly via regulation of neuropeptide release. The goal of this study was to determine whether capsaicin, which selectively activates primary afferent neurons and evokes neuropeptide release, acts in an NO-dependent manner. Our results indicate that capsaicin (1 microM)-evoked release of immunoreactive calcitonin gene-related peptide (iCGRP) is significantly reduced in the presence of the NO synthase inhibitor, L-NAME (10-400 nM; F(3,45)=68.38; P<0.001) and, the selective nNOS inhibitor, 3-bromo-7-nitroindazole (170-680 nM; F(5,48)=56.2; P<0. 01). D-NAME (200 nM) had no effect on capsaicin-evoked iCGRP release. Hemoglobin (an extracellular scavenger of NO; 3 mg/ml) significantly reduced the effect of capsaicin on the release of iCGRP (F(1,8)=9.12; P<0.05). The NOS substrate, L-arginine, effectively reversed the inhibitory effect of 3-bromo-7-nitroindazole on capsaicin-evoked iCGRP release. To determine whether the NO-mediated release was NMDA-driven, we superfused spinal cord slices with competitive and non-competitive NMDA antagonists in the presence and absence of capsaicin. MK-801 (0. 1-10 microM; F(4,33)=8.49; P<0.0001) and AP-5 (0.01-10 microM; F(4, 38)=3.34; P<0.05) reduced capsaicin-evoked iCGRP release. CNQX, an AMPA/kainate antagonist (10 nM-10 microM), significantly decreased capsaicin-evoked release of iCGRP (F(6,42)=8.76; P<0.01) in a dose-dependent fashion. Additionally, our results demonstrate that while capsaicin-evoked release is significantly reduced in the presence of LY-83583 (10 microM; F(2,18)=3.46; P<0.01; a cyclic GMP lowering agent), there is no effect of ODQ (a potent and selective inhibitor of guanylate cyclase). Moreover, the application of a cell permeable analog of cyclic GMP (8-bromo-cGMP; 0.01-1000 microM) is without effect on both basal and evoked iCGRP release. Finally, we observed no colocalization of immunoreactive neuronal NOS (nNOS) with CGRP in the dorsal horn. In summary, these data indicate that capsaicin evokes the release of iCGRP, in part, via the production of NO which enters the extracellular space prior to having an effect. Moreover, iCGRP and nNOS are produced in distinct populations of neurons within the dorsal horn. We conclude that capsaicin-evoked release involves the activation of the NMDA receptor but is also modified by the activation of AMPA or kainate receptors. Finally, these data suggest that while capsaicin-evoked iCGRP release is modified by NO, this release does not require the activation of guanylate cyclase and subsequent production of cyclic GMP.