The Effect of Capsaicin Derivatives on Tight-Junction Integrity and Permeability of Madin-Darby Canine Kidney Cells

Comparative effectiveness of nitro dihydrocapsaicin, new synthetic derivative capsaicinoid, and capsaicin in alleviating oxidative stress and inflammation on lipopolysaccharide-stimulated corneal epithelial cells

Loss of tear homeostasis, characterized by hyperosmolarity of the ocular surface, induces cell damage through inflammation and oxidation. Transient receptor potential vanilloid 1 (TRPV1), a sensor for osmotic changes, plays a crucial role as a calcium ion channel in the pathogenesis of hypertonic-related eye diseases. Capsaicin (CAP), a potent phytochemical, alleviates inflammation during oxidative stress events by activating TRPV1. However, the pharmacological use of CAP for eye treatment is limited by its pungency. Nitro dihydrocapsaicin (NDHC) was synthesized with aromatic ring modification of CAP structure to overcome the pungent effect. We compared the molecular features of NDHC and CAP, along with their biological activities in human corneal epithelial (HCE) cells, focusing on antioxidant and anti-inflammatory activities. The results demonstrated that NDHC maintained cell viability, cell shape, and exhibited lower cytotoxicity compared to CAP-treated cells. Moreover, NDHC prevented oxidative stress and inflammation in HCE cells following lipopolysaccharide (LPS) administration. These findings underscore the beneficial effect of NDHC in alleviating ocular surface inflammation, suggesting that NDHC may serve as an alternative anti-inflammatory agent targeting TRPV1 for improving hyperosmotic stress-induced ocular surface damage.

Spice Up Your Kidney: A Review on the Effects of Capsaicin in Renal Physiology and Disease

Capsaicin, the organic compound which attributes the spicy flavor and taste of red peppers and chili peppers, has been extensively studied for centuries as a potential natural remedy for the treatment of several illnesses. Indeed, this compound exerts well-known systemic pleiotropic effects and may thus bring important benefits against various pathological conditions like neuropathic pain, rhinitis, itching, or chronic inflammation. Yet, little is known about the possible biological activity of capsaicin at the kidney level, as this aspect has only been addressed by sparse experimental investigations. In this paper, we aimed to review the available evidence focusing specifically on the effects of capsaicin on renal physiology, as well as its potential benefits for the treatment of various kidney disorders. Capsaicin may indeed modulate various aspects of renal function and renal nervous activity. On the other hand, the observed experimental benefits in preventing acute kidney injury, slowing down the progression of diabetic and chronic kidney disease, ameliorating hypertension, and even delaying renal cancer growth may set the stage for future human trials of capsaicin administration as an adjuvant or preventive therapy for different, difficult-to-treat renal diseases.

Capsaicin indirectly regulates TRPA1 via the arachidonic acid cascade, resulting in TJ opening

Capsaicin induces the reversible opening of tight junctions (TJs) and enhances the delivery of hydrophilic macromolecules through a paracellular route. We previously revealed that TRPA1 is involved in the capsaicin-induced Ca2+ influx and TJ permeability increase, although there are no reports that capsaicin directly activates TRPA1. In this study, we investigated the upstream factors of TRPA1 using RNA-seq analysis, and found that the cyclooxygenase 2 (COX2) gene was upregulated by capsaicin. Cyclooxygenase 2 converts arachidonic acid (AA), a metabolite by phospholipase A2 (PLA2), to prostaglandins. Prostaglandin E2 (PGE2) production was stimulated by capsaicin, and capsaicin-induced Ca2+ influx was effectively inhibited by PLA2 and COX2 inhibitors. The AA-induced TJ permeability increase was inhibited by a TRPA1 antagonist, but the capsaicin- and AA-induced TJ permeability increases were hardly inhibited by a COX2 inhibitor. These results suggest that capsaicin-induced PLA2 activation and AA production are the important steps for the TJ permeability increase.

Electrophilic amidomethylation of arenes with DMSO/MeCN reagents

An efficient electrophilic amidomethylation of aromatics was described with DMSO as the CH2 source and nitrile as the nitrogen source.

Lactobacillus rhamnosus attenuates Thai chili extracts induced gut inflammation and dysbiosis despite capsaicin bactericidal effect against the probiotics, a possible toxicity of high dose capsaicin

Because of a possible impact of capsaicin in the high concentrations on enterocyte injury (cytotoxicity) and bactericidal activity on probiotics, Lactobacillus rhamnosus L34 (L34) and Lactobacillus rhamnosus GG (LGG), the probiotics derived from Thai and Caucasian population, respectively, were tested in the chili-extract administered C57BL/6 mice and in vitro experiments. In comparison with placebo, 2 weeks administration of the extract from Thai chili in mice caused loose feces and induced intestinal permeability defect as indicated by FITC-dextran assay and the reduction in tight junction molecules (occludin and zona occludens-1) using fluorescent staining and gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the chili extracts also induced the translocation of gut pathogen molecules; lipopolysaccharide (LPS) and (1→3)-β-d-glucan (BG) and fecal dysbiosis (microbiome analysis), including reduced Firmicutes, increased Bacteroides, and enhanced total Gram-negative bacteria in feces. Both L34 and LGG attenuated gut barrier defect (FITC-dextran, the fluorescent staining and gene expression of tight junction molecules) but not improved fecal consistency. Additionally, high concentrations of capsaicin (0.02-2 mM) damage enterocytes (Caco-2 and HT-29) as indicated by cell viability test, supernatant cytokine (IL-8), transepithelial electrical resistance (TEER) and transepithelial FITC-dextran (4.4 kDa) but were attenuated by Lactobacillus condition media (LCM) from both probiotic-strains. The 24 h incubation with 2 mM capsaicin (but not the lower concentrations) reduced the abundance of LGG (but not L34) implying a higher capsaicin tolerance of L34. However, Lactobacillus rhamnosus fecal abundance, using qRT-PCR, of L34 or LGG after 3, 7, and 20 days of the administration in the Thai healthy volunteers demonstrated the similarity between both strains. In conclusion, high dose chili extracts impaired gut permeability and induced gut dysbiosis but were attenuated by probiotics. Despite a better capsaicin tolerance of L34 compared with LGG in vitro, L34 abundance in feces was not different to LGG in the healthy volunteers. More studies on probiotics with a higher intake of chili in human are interesting.

The Influence of Capsaicin on the Integrity of Microvascular Endothelial Cell Monolayers

Microvascular endothelial cells are an essential part of many biological barriers, such as the blood⁻brain barrier (BBB) and the endothelium of the arteries and veins. A reversible opening strategy to increase the permeability of drugs across the BBB could lead to improved therapies due to enhanced drug bioavailability. Vanilloids, such as capsaicin, are known to reversibly open tight junctions of epithelial and endothelial cells. In this study, we used several in vitro assays with the murine endothelial capillary brain cells (line cEND) as a BBB model to characterize the interaction between capsaicin and endothelial tight junctions.

Intestinal absorption of black chokeberry cyanidin 3-glycosides is promoted by capsaicin and capsiate in a rat ligated small intestinal loop model

Recent studies have shown that aronia (black chokeberry) and haskap fruits (contain anthocyanins) have beneficial health effects in animals and humans. However, some reports have shown that anthocyanin is poorly absorbed in the small intestine. In this study, we compared the intestinal absorption of aronia and haskap anthocyanins by using rats with a ligated small intestinal loop and cannulated portal vein. Our results clearly showed that the intestinal absorption of aronia anthocyanins was significantly lower than that of haskap anthocyanins, suggesting that the intestinal absorption of anthocyanins is influenced by the glycoside type (galactoside or glucoside). In addition, we also examined the effects of capsaicin and capsiate on intestinal anthocyanin absorption. The amount of aronia anthocyanins in portal blood was much higher when they were co-administered with capsaicin or capsiate. Our study is the first to show that the intestinal absorption of aronia anthocyanins is promoted by capsaicin and capsiate.

TRPA1-dependent reversible opening of tight junction by natural compounds with an α,β-unsaturated moiety and capsaicin

The delivery of hydrophilic macromolecules runs into difficulties such as penetration of the cell membrane lipid bilayer. Our prior experiment demonstrated that capsaicin induces the reversible opening of tight junctions (TJs) and enhances the delivery of hydrophilic macromolecules through a paracellular route. Herein, we screened paracellular permeability enhancers other than capsaicin. As TJ opening by capsaicin is associated with Ca²⁺ influx, we first screened the compounds that induce Ca²⁺ influx in layered MDCK II cells, and then we determined the compounds' abilities to open TJs. Our results identified several natural compounds with α,β-unsaturated moiety. A structure-activity relationship (SAR) analysis and the results of pretreatment with reducing reagent DTT suggested the importance of α,β-unsaturated moiety. We also examined the underlying mechanisms, and our findings suggest that the actin reorganization seen in capsaicin treatment is important for the reversibility of TJ opening. Furthermore, our analyses revealed that TRPA1 is involved in the Ca²⁺ influx and TJ permeability increase not only by an α,β-unsaturated compound but also by capsaicin. Our results indicate that the α,β-unsaturated moiety can be a potent pharmacophore for TJ opening.