Developmental Toxicity Study of Pure trans-Capsaicin in Rats and Rabbits

Capsicum annuum L. and its bioactive constituents: A critical review of a traditional culinary spice in terms of its modern pharmacological potentials with toxicological issues

Capsicum annuum L., commonly known as chili pepper, is used as an important spice globally and as a crude drug in many traditional medicine systems. The fruits of C. annuum have been used as a tonic, antiseptic, and stimulating agent, to treat dyspepsia, appetites, and flatulence, and to improve digestion and circulation. The article aims to critically review the phytochemical and pharmacological properties of C. annuum and its major compounds. Capsaicin, dihydrocapsaicin, and some carotenoids are reported as the major active compounds with several pharmacological potentials especially as anticancer and cardioprotectant. The anticancer effect of capsaicinoids is mainly mediated through mechanisms involving the interaction of Ca²⁺ -dependent activation of the MAPK pathway, suppression of NOX-dependent reactive oxygen species generation, and p53-mediated activation of mitochondrial apoptosis in cancer cells. Similarly, the cardioprotective effects of capsaicinoids are mediated through their interaction with cellular transient receptor potential vanilloid 1 channel, and restoration of calcitonin gene-related peptide via Ca²⁺ -dependent release of neuropeptides and suppression of bradykinin. In conclusion, this comprehensive review presents detailed information about the traditional uses, phytochemistry, and pharmacology of major bioactive principles of C. annuum with special emphasis on anticancer, cardioprotective effects, and plausible toxic adversities along with food safety.

Changes in TRPV1-Mediated Physiological Function in Rats Systemically Treated With Capsaicin on the Neonate

Capsaicin is the active component of chili peppers and is a hydrophobic, colorless, odorless, and crystalline to waxy compound. The transient receptor potential vanilloid 1 (TRPV1) is the capsaicin receptor channels that are involved in a variety of functions like transduction and transmission of the physiological stimulus. Subcutaneous injection of capsaicin to a newborn rat leads to involuntary lifelong TRPV1 desensitization. Various physiological changes including sensory and homeostatic actions in the body associated with neonatal capsaicin treatment are induced by direct TRPV1 channel targeting. Interesting changes include unique phenomena such as the reduction in pain perception, abnormal body temperature, increase in infection, infectious or neuropathological itching, and irregular circadian core body temperature rhythm. These symptoms are associated with relatively higher fever or loss of sensory c-fiber related to TRPV1 desensitization. The aforementioned outcomes not only provide a warning about the risk of capsaicin exposure in newborns but also indicate the possible occurrence of relatively rare diseases that are difficult to diagnose. Therefore, Therefore, the present review aims to summarize the unique phenomena caused by systemic capsaicin administration in neonatal rats.

Changes in TRPV1-Mediated Physiological Function in Rats Systemically Treated With Capsaicin on the Neonate

Capsaicin is the active component of chili peppers and is a hydrophobic, colorless, odorless, and crystalline to waxy compound. The transient receptor potential vanilloid 1 (TRPV1) is the capsaicin receptor channels that are involved in a variety of functions like transduction and transmission of the physiological stimulus. Subcutaneous injection of capsaicin to a newborn rat leads to involuntary lifelong TRPV1 desensitization. Various physiological changes including sensory and homeostatic actions in the body associated with neonatal capsaicin treatment are induced by direct TRPV1 channel targeting. Interesting changes include unique phenomena such as the reduction in pain perception, abnormal body temperature, increase in infection, infectious or neuropathological itching, and irregular circadian core body temperature rhythm. These symptoms are associated with relatively higher fever or loss of sensory c-fiber related to TRPV1 desensitization. The aforementioned outcomes not only provide a warning about the risk of capsaicin exposure in newborns but also indicate the possible occurrence of relatively rare diseases that are difficult to diagnose. Therefore, Therefore, the present review aims to summarize the unique phenomena caused by systemic capsaicin administration in neonatal rats.

Assessment of Pharmacology, Safety, and Metabolic activity of Capsaicin Feeding in Mice

Capsaicin (CAP) activates transient receptor potential vanilloid subfamily 1 (TRPV1) to counter high-fat diet (HFD)-induced obesity. Several studies suggest that CAP induces the browning of white adipocytes in vitro or inguinal white adipose tissue (iWAT) in vivo. However, there is a lack of data on the dose-response for CAP to inhibit HFD-induced obesity. Therefore, we first performed experiments to correlate the effect of various doses of CAP to prevent HFD-induced weight gain in wild-type (WT) mice. Next, we performed a subchronic safety study in WT mice fed a normal chow diet (NCD ± CAP, 0.01% in NCD) or HFD ± CAP (0.01% in HFD) for eight months. We analyzed the expression of adipogenic and thermogenic genes and proteins in the iWAT from these mice, conducted histological studies of vital organs, measured the inflammatory cytokines in plasma and iWAT, and evaluated liver and kidney functions. The dose-response study showed that CAP, at doses above 0.001% in HFD, countered HFD-induced obesity in mice. However, no difference in the anti-obesity effect of CAP was observed at doses above 0.003% in HFD. Also, CAP, above 0.001%, enhanced the expression of sirtuin-1 and thermogenic uncoupling protein 1 (UCP-1) in the iWAT. Safety analyses suggest that CAP did not cause inflammation. However, HFD elevated plasma alanine aminotransferase and creatinine, caused iWAT hypertrophy and hepatic steatosis, and CAP reversed these. Our data suggest that CAP antagonizes HFD-induced metabolic stress and inflammation, while it does not cause any systemic toxicities and is well tolerated by mice.

Studies of the Toxicological Potential of Capsinoids: IV. Teratology Studies of CH-19 Sweet Extract in Rats and Rabbits

In order to evaluate the safety of CH-19 Sweet extract that contains capsinoids, teratology studies were conducted in pregnant Sprague-Dawley rats (20 rats per group) and pregnant New Zealand white rabbits (17 to 22 animals per group). The test substance was administered to rats by gavage for 11 days on gestation days 7 to 17 at doses of 0 (vehicle), 1.25, 2.5, and 5.0 ml/kg and to rabbits for 13 days on gestation days 6 to 18 at doses of 0 (vehicle), 0.25, 0.5, and 1.0 ml/kg. As the concentration of capsinoids in CH-19 Sweet extract was 72.2 to 75.05 mg/ml, the resulting dose of capsinoids administered to rats was 90.25, 180.5, and 361 mg/kg, and to rabbits was 18.76, 37.53, and 75.05 mg/kg in the vehicle, low-, mid-, and high-dose groups, respectively. In the rat study, no deaths occurred in any group and there were no test substance–related changes or abnormalities in clinical signs, body weight, food consumption, or gross pathological findings. There were no test substance–related changes in the number of corpora lutea, number or index of implantations, index of embryofetal deaths, number of live fetuses, sex ratio, fetal body weight at the end of the gestation period, or abnormalities in the placenta of live fetuses. There were no test substance–related abnormalities or variations in the external, skeletal, or visceral examinations of live fetuses. It was concluded that the test article caused neither teratogenic effects nor abnormalities in the progression of ossification. In the rabbit study, there were no test substance–related effects on clinical signs, body weight, food consumption, or necropsy findings. There were neither test substance–related abortions nor test substance–related effects on the number of corpora lutea, or number or index of implantations. There were no test substance–related effects on the number of dead embryos/fetuses, the number of live fetuses, sex ratio, body weight of live fetuses, or gross pathological finding in the placentas. There were no test substance–related external abnormalities or incidences of visceral or skeletal abnormalities or variations, and there were no test substance–related effects on the progress of ossification in any group. The authors concluded the no observed adverse effect level (NOAEL) of CH-19 Sweet extract containing capsinoids on pregnant animals and fetal development/growth was >5.0 ml/kg/day (>361 mg/kg/day as capsinoids) in rats and >1.0 ml/kg/day (>75.05 mg/kg/day as capsinoids) in rabbits.

Studies of the Toxicological Potential of Capsinoids: IX. Teratology Studies of Dihydrocapsiate in Rats and Rabbits

In order to determine the safety of dihydrocapsiate (4-hydroxy-3-methoxybenzyl 8-methylnonanoate; CAS no. 205687-03-2), teratology studies were conducted in pregnant Sprague-Dawley rats (18 to 20 animals per group) and pregnant New Zealand white rabbits (20 to 21 animals per group). The test substance was administered by gavage for 11 days, from days 7 to 17 of gestation in rats, and for 13 days from days 6 to 18 of gestation in rabbits, at dose levels of 0 (vehicle), 100, 300, or 1000 mg/kg/day. In the rat study, no deaths occurred in any group and there were no test substance–related changes or abnormalities in clinical signs, body weight, food consumption, or gross pathological findings. There were no test substance–related changes in the number of corpora lutea, number of implantations, index of implantations, index of embryofetal deaths, and number, sex ratio, or body weight of live fetuses at the end of the gestation period and there were no abnormalities in the placentae of live fetuses. There were no test substance–related abnormalities or variations in the external, skeletal, or visceral examinations of live fetuses. There were no abnormalities in ossification. En toto, it was concluded there were no teratogenic effects in the rat study. In the rabbit study, there were no test substance–related effects on clinical signs, body weight, food consumption, or necropsy findings in any group. There were neither test substance–related abortions nor test substance–related effects on the number of corpora lutea, number of implantations, or implantation index in any group. There were no test substance–related effects on the number of dead embryos/fetuses, the number, sex ratio, or body weight of live fetuses, or gross pathological finding of placentae. There were no test substance–related external abnormalities, or incidence of visceral or skeletal abnormalities or variations, and there were no test substance–related effects on the progress of ossification in any group. Based upon these data, the no observed adverse effect level (NOAEL) of dihydrocapsiate for general toxicity in dams, reproductive functions of dams, and embryofetal development was judged to be 1000 mg/kg/day both in rats and rabbits.

A 90-day toxicity and genotoxicity study with high-purity phenylcapsaicin

To evaluate the safety of the synthetic capsaicin analogue phenylcapsaicin (PheCap; 7-phenylhept-6-yne-acid-hydroxy-3-mathoxylbenzylamide, CAS no 848127-67-3), a 90-day repeated dose oral gavage of 0, 30, 100 or 250 mg/kg body weight (bw)/day toxicity study with a 28-day recovery period was conducted using Wistar rats. Examinations of clinical signs, body and organ weight, haematology, urinalysis, clinical chemistry, food consumption and macroscopic, as well as histopathological tissue examinations were carried out for signs of toxicity. Degenerative, but reversible changes in the liver at 250 mg/kg bw/day, and local irritating effects in the stomach at 100 and 250 mg/kg bw/day were found. These findings were associated with test item-related clinical symptoms, that is, diarrhoea, salivation and moving of bedding material. PheCap did neither cause gene mutations by base pair changes or frame shifts in the genome of the tester stains Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537 or TA 102 nor induce structural and/or numerical chromosomal damage in human lymphocytes. Therefore, it can be concluded that PheCap is not genotoxic. The No Observed Adverse Effect Level (NOAEL) of PheCap for systemic toxicity is considered to be at 100 mg/kg bw/day which is based on degenerative changes in the liver. Due to irritating effects in the stomach, the NOAEL for local effects was established at 30 mg/kg bw/day.

Food Aversions and Cravings during Pregnancy on Yasawa Island, Fiji

Women often experience novel food aversions and cravings during pregnancy. These appetite changes have been hypothesized to work alongside cultural strategies as adaptive responses to the challenges posed by pregnancy (e.g., maternal immune suppression). Here, we report a study that assessed whether data from an indigenous population in Fiji are consistent with the predictions of this hypothesis. We found that aversions focus predominantly on foods expected to exacerbate the challenges of pregnancy. Cravings focus on foods that provide calories and micronutrients while posing few threats to mothers and fetuses. We also found that women who experience aversions to specific foods are more likely to crave foods that meet nutritional needs similar to those provided by the aversive foods. These findings are in line with the predictions of the hypothesis. This adds further weight to the argument that appetite changes may function in parallel with cultural mechanisms to solve pregnancy challenges.

Biological Activities of Red Pepper (Capsicum annuum) and Its Pungent Principle Capsaicin: A Review

Capsaicin, the pungent alkaloid of red pepper (Capsicum annuum) has been extensively studied for its biological effects which are of pharmacological relevance. These include: cardio protective influence, antilithogenic effect, antiinflammatory, and analgesia, thermogenic influence, and beneficial effects on gastrointestinal system. Therefore, capsaicinoids may have the potential clinical value for pain relief, cancer prevention and weight loss. It has been shown that capsaicinoids are potential agonists of capsaicin receptor (TRPV1). They could exert the effects not only through the receptor-dependent pathway but also through the receptor-independent one. The involvement of neuropeptide Substance P, serotonin, and somatostatin in the pharmacological actions of capsaicin has been extensively investigated. Topical application of capsaicin is proved to alleviate pain in arthritis, postoperative neuralgia, diabetic neuropathy, psoriasis, etc. Toxicological studies on capsaicin administered by different routes are documented. Capsaicin inhibits acid secretion, stimulates alkali and mucus secretion and particularly gastric mucosal blood flow which helps in prevention and healing of gastric ulcers. Antioxidant and antiinflammatory properties of capsaicin are established in a number of studies. Chemopreventive potential of capsaicin is evidenced in cell line studies. The health beneficial hypocholesterolemic influence of capsaicin besides being cardio protective has other implications, viz., prevention of cholesterol gallstones and protection of the structural integrity of erythrocytes under conditions of hypercholesterolemia. Beneficial influences of capsaicin on gastrointestinal system include digestive stimulant action and modulation of intestinal ultrastructure so as to enhance permeability to micronutrients.

Environmental challenge, epigenetic plasticity and the induction of altered phenotypes in mammals

The level of transcriptional activity of a gene is regulated by epigenetic processes. There is compelling evidence that environmental challenges throughout the life course can induce phenotypic change. In this review, we summarize the current evidence, focusing specifically on the effects of nutrition and of environmental pollutants, that epigenetic processes underpin the induction by environmental change of altered phenotypic traits, emphasizing the implications for health outcomes. We also discuss whether epigenetic processes may be involved in the passage of induced traits between generations. Overall, current findings indicate that epigenetic processes may play an important role in determining disease risk, but there is a lack of studies that demonstrate causal links between epigenetic change and tissue function.

A framework incorporating the impact of exposure scenarios and application conditions on risk assessment of chemicals applied to skin

PURPOSE

1. To develop a framework for exposure calculation via the dermal route to meet the needs of 21st century toxicity testing and refine current approaches; 2. To demonstrate the impact of exposure scenario and application conditions on the plasma concentration following dermal exposure.

METHOD

A workflow connecting a dynamic skin penetration model with a generic whole-body physiologically-based pharmacokinetic (PBPK) model was developed. The impact of modifying exposure scenarios and application conditions on the simulated steady-state plasma concentration and exposure conversion factor was investigated for 9 chemicals tested previously in dermal animal studies which did not consider kinetics in their experimental designs.

RESULTS

By simulating the animal study scenarios and exposure conditions, we showed that 7 studies were conducted with finite dose exposures, 1 with both finite and infinite dose exposures (in these 8 studies, an increase in the animal dose resulted in an increase in the simulated steady-state plasma concentrations (C p,ss)), while 1 study was conducted with infinite dose exposures only (an increase in the animal dose resulted in identical C p,ss). Steady-state plasma concentrations were up to 30-fold higher following an infinite dose scenario vs. a finite dose scenario, and up to 40-fold higher with occlusion vs. without. Depending on the chemical, the presence of water as a vehicle increased or decreased the steady-state plasma concentration, the largest difference being a factor of 16.

CONCLUSIONS

The workflow linking Kasting's model of skin penetration and whole-body PBPK enables estimation of plasma concentrations for various applied doses, exposure scenarios and application conditions. Consequently, it provides a quantitative, mechanistic tool to refine dermal exposure calculations methodology for further use in risk assessment.

Capsaicin for neuropathic pain: linking traditional medicine and molecular biology

Capsaicin has long been used as a traditional medicine to treat pain and, recently, its mechanism of analgesic action has been discovered. This review article documents the clinical development of capsaicin to demonstrate that pharmacognosy still has a profound influence on modern-day drug development programs. Capsaicin is a highly selective agonist for the transient receptor potential channel vanilloid-receptor type 1 (TRPV1), which is expressed on central and peripheral terminals of nociceptive primary sensory neurons. Knockout studies have revealed the importance of TRPV1 as a molecular pain integrator and target for novel analgesic agents. Topical application of capsaicin at the peripheral terminal of TRPV1-expressing neurons superficially denervates the epidermis in humans in a highly selective manner and results in hypoalgesia. In three recent randomized controlled trials, a patch containing high-concentration capsaicin demonstrated meaningful efficacy and tolerability relative to a low-concentration capsaicin control patch in patients with peripheral neuropathic pain. Data from clinical practice will determine if the high-concentration capsaicin patch is effective in real-world settings.

Treatment of cluster headache in pregnancy and lactation

Cluster headache is a rare disorder in women, but has a serious impact on the affected woman's life, especially on family planning. Women with cluster headache who are pregnant need special support, including the expertise of an experienced headache centre, an experienced gynaecologist and possibly a teratology information centre. The patient should be seen through all stages of the pregnancy. A detailed briefing about the risks and safety of various treatment options is mandatory. In general, both the number of medications and the dosage should be kept as low as possible. Preferred treatments include oxygen, subcutaneous or intranasal sumatriptan for acute pain and verapamil and prednisone/prednisolone as preventatives. If there is a compelling reason to treat the patient with another preventative, gabapentin is the drug of choice. While breastfeeding, oxygen, sumatriptan and lidocaine for acute pain and prednisone/prednisolone, verapamil, and lithium as preventatives are the drugs of choice. As the individual pharmacokinetics differ substantially, adverse drug effects should be considered if unexplained symptoms occur in the newborn.