The Multiple Roles of Urocanic Acid in Health and Disease.

Trans-urocanic acid (trans-UCA) is synthesized in the skin, liver, and brain. It is a major natural moisturizing factor in skin and maintains its acid pH. In skin, it isomerizes to cis-UCA following exposure to UVR. Both isomers fulfill multiple roles in health and disease. Cis-UCA has immunomodulatory properties linked with several cutaneous diseases such as skin cancer, atopic dermatitis, and urticaria and associates with systemic diseases including multiple sclerosis. The levels of UCA in the skin, brain, urine, and feces reflect some physiological processes and may be disease biomarkers. Both isomers of UCA have therapeutic potential for a range of disorders.

Trans-urocanic acid enhances tenofovir alafenamide stability for long-acting HIV applications.

Long-acting (LA) pre-exposure prophylaxis (PrEP) for HIV prevention is poised to address non-adherence and implementation challenges by alleviating the burden of user-dependent dosing. Due to its potency, tenofovir alafenamide (TAF) is a viable candidate for LA PrEP. However, the inherent hydrolytic instability of TAF presents a challenge for application in LA systems. In this work, we examined the mechanism of TAF hydrolysis in a reservoir-based implant system and characterized TAF degradation kinetics as a function of the solution pH. We determined a pH "stability window" between pH 4.8 - 5.8 in which TAF degradation is substantially mitigated, with minimal degradation at pH 5.3. In a pursuit of a TAF formulation suitable for LA PrEP, we studied trans-urocanic acid (UA) as a buffer excipient. Here we show that UA can maintain the pH of TAF free base (TAFfb) solution inside a surrogate implant model at approximately pH 5.4. Through in vitro analysis, we demonstrated preservation of released TAF purity above 90% for over 9 months. Further, we performed an in vivo assessment of TAFfb-UA formulation in a reservoir-based nanofluidic implant inserted subcutaneously in non-human primates. Preventive levels of tenofovir diphosphate above 100 fmol/106 peripheral blood mononuclear cells were achieved in 2 days and sustained over 35 days. Fluid retrieved from implants after 60 days of implantation showed that UA preserved the aqueous phase in the implant at ~ pH 5.5, effectively counteracting the neutralizing action of interstitial fluids. Moreover, residual TAF in the implants maintained > 98% purity. Overall, TAF-UA represents a viable formulation applicable for LA HIV PrEP.

Intravesical treatment with cis-urocanic acid improves bladder function in rat model of acute bladder inflammation.

AIMS: The aim was to study the effect of intravesically instilled cis-urocanic acid (cis-UCA) on bladder function in an experimental rat model of acute bladder inflammation. Hyaluronic acid (HA) was used as a comparator compound. METHODS: Bladder irritation was induced in female rats by intravesical hydrochloric acid (HCl) infusion. Vehicle, 0.5% HA, or 2% cis-UCA solutions were infused intravesically twice a day for three consequent days. On the fourth day, urodynamical measurements were performed, the animals were sacrificed, and the bladders were removed for histopathological assessment. RESULTS: HCl treatment caused significant impairment of bladder function indicated by decreased micturition intervals and voided urine volumes and induced severe voiding dysfunction observed as occurrence of overflow incontinence. These functional changes were accompanied by increased bladder weight, hemorrhage, and infiltration of inflammatory cells into the urothelium. Intravesical cis-UCA treatment recovered bladder function by significantly prolonging the micturition interval, increasing the voided volume, and reducing the occurrence of overflow incontinence. All these changes were comparable to the effects of HA. CONCLUSIONS: Intravesical administration of cis-UCA was able to partially recover bladder function impaired by chemical irritation. Cis-UCA may offer a novel intravesical treatment option in some inflammatory conditions of the bladder. Neurourol. Urodynam. 35:786-791, 2016. © 2015 Wiley Periodicals, Inc.

What's new in the topical treatment of allergic skin diseases.

PURPOSE OF REVIEW: To review recent literature on the topical treatment of allergic skin diseases to help clinicians make informed evidence-based decisions. RECENT FINDINGS: Twenty-four publications were identified from a PubMed search of randomized controlled trials and systematic reviews of topical treatment of atopic dermatitis and allergic contact dermatitis published from 1 January 2013 to 31 January 2014. Studies on the topical treatment of atopic dermatitis largely supported the recommended use of topical corticosteroids and topical calcineurin inhibitors. Barrier therapy continues to play an important role without evidence supporting use of one emollient over another. Lipoxin A4, an eicosanoid with anti-inflammatory properties, and a 5% cis-urocanic acid emulsion cream were effective in the treatment of atopic dermatitis, although studies were small. Adjunct therapy with bleach baths, natural oils, and textiles all showed some benefit; however, studies are limited. Literature on topical treatment of allergic contact dermatitis was limited to one publication, providing evidence for a natural multicomponent cream as maintenance therapy after control of disease with a topical corticosteroid. SUMMARY: There is strong evidence for the use of topical anti-inflammatory therapies in the treatment of atopic dermatitis. There is little evidence to suggest that one emollient is better than others.

Antitumor effects of cis-urocanic acid on experimental urothelial cell carcinoma of the bladder.

PURPOSE: We determined the effect of protodynamic therapy against bladder cancer cells in vitro and in vivo. We investigated cis-urocanic acid in rat bladder cancer cell cultures and in an orthotopic rat urothelial carcinoma model to assess its safety and antiproliferative activity. MATERIALS AND METHODS: The rat bladder cancer cell line AY-27 was exposed to cis-urocanic acid (BioCis Pharma, Turku, Finland) at pH 6.5 or 7.4 for 2 hours. Cell viability was measured by colorimetric assay at 24 and 48 hours. For in vivo experiments AY-27 cells were instilled into the acid treated bladder of 17 rats. After 4, 7 and 10 days 14 rats were treated intravesically with cis-urocanic acid 6% (weight per volume) or vehicle. Rats were sacrificed on day 12 and the bladders were dissected. Immunohistochemical staining was done to assess apoptosis (caspase-3) and cell proliferation (Ki-67) in vivo. RESULTS: Cis-urocanic acid caused dose dependent, pH dependent inhibition of AY-27 cell proliferation, showing the protodynamic action at concentrations of 0.5% and 1%. At higher cis-urocanic acid doses complete cell death was observed. All tumors detected in animals treated with vehicle were muscle invasive (stage T2 or greater) but only 43% of tumors were muscle invasive in the cis-urocanic acid treated group (p=0.049). There was no difference in the percent of apoptotic or proliferating tumor cells between treatment groups. No signs of toxicity were observed. CONCLUSIONS: Cis-urocanic acid showed direct antiproliferative activity against rat bladder cancer cells in vitro and antitumor effects in vivo. It may have therapeutic potential as an intravesical agent for nonmuscle invasive bladder cancer.

Cis-urocanic acid inhibits SAPK/JNK signaling pathway in UV-B exposed human corneal epithelial cells in vitro.

PURPOSE: The cornea is sensitive to ultraviolet B (UV-B) radiation-induced oxidative stress and inflammation. Its clinical manifestations are photokeratitis and climatic droplet keratopathy. Urocanic acid (UCA) is a major endogenous UV-absorbing chromophore in the epidermis and it is also an efficacious immunosuppressant. We have previously shown that cis-UCA can suppress UV-B-induced interleukin-6 and -8 secretion and cytotoxicity in human corneal epithelium (HCE) cells. In the current study, we further wanted to investigate the effects of cis-UCA on UV-B-induced inflammatory and apoptotic responses in HCE-2 cells, focusing on the nuclear factor kappa B (NF-κB) and AP-1 (subunits c-Fos and c-Jun) signaling pathways. METHODS: After exposing HCE-2 cells to UV-B and cis-UCA, DNA binding of c-Fos, c-Jun and NF-κB was measured with ELISA. In addition, the endogenous levels of phosphorylated stress-activated protein kinase/c-Jun N-terminal kinase (phospho-SAPK/JNK) and phospho-c-Jun were determined. The proliferative capacity of HCE-2 cells was also quantified, and the cytotoxicity of the cis-UCA and UV-B treatments was monitored by measuring the release of lactate dehydrogenase enzyme in the culture medium. RESULTS: UV-B irradiation induced the binding of transcription factors c-Jun, c-Fos, and NF-κB to DNA. Cis-UCA inhibited the binding of c-Jun and c-Fos but not that of NF-κB. Moreover, UV-B increased the levels of phospho-c-Jun and phospho-JNK, and the expression of both was attenuated by cis-UCA. Cis-UCA also alleviated the UV-B-induced apoptosis and proliferative decline in human corneal cells. CONCLUSIONS: The results from this study suggest that cis-UCA suppresses JNK signaling pathway, which provides potential for treating UV-B-induced inflammatory defects in human corneal cells.

Treatment of contact hypersensitivity with urocanic acid.

In order to investigate the effect of cis-urocanic acid (UCA) on a delayed-type hypersensitivity response in humans, a contact hypersensitivity reaction was induced on four test sites on the back of 33 volunteer subjects. The first test site was pretreated with cis-UCA immediately before application of the allergen. The second and third test sites were posttreated on the second and third days of the hypersensitivity response with cis-UCA and a class III corticosteroid, respectively. The fourth test site was used as a positive control. The cutaneous blood flow of the test sites was measured using laser Doppler flowmetry. Pretreatment with cis-UCA reduced the hypersensitivity response significantly. It is possible that cis-UCA could be used in the preventive treatment of contact hypersensitivity responses.

A garlic extract protects from ultraviolet B (280-320 nm) radiation-induced suppression of contact hypersensitivity.

Lyophilized aged garlic extract has been incorporated at concentrations of 0.1%, 1% and 4% by weight into semipurified powdered diets and fed to hairless mice. Under moderate UVB exposure conditions resulting in 58% suppression of the systemic contact hypersensitivity response in control-fed mice, a dose-responsive protection was observed in the garlic-fed mice; contact hypersensitivity in the UVB-exposed mice fed 4% garlic extract was suppressed by only 19%. If the UVB exposure was replaced by topical application of one of a series of lotions containing increasing concentrations of cis-urocanic acid, a dose-responsive suppression of contact hypersensitivity was demonstrated in control-fed mice (urocanic acid at 25, 50, 100 and 200 micrograms per mouse resulting in 22-46% suppression). Mice fed a diet containing 1% aged garlic extract were partially protected from cis-urocanic acid-induced suppression of contact hypersensitivity, with greater protection from the lower concentrations of urocanic acid. Mice fed a diet containing 4% aged garlic extract were protected from all concentrations of urocanic acid. The results indicate that aged garlic extract contains ingredient(s) that protect from UVB-induced suppression of contact hypersensitivity and suggest that the mechanism of protection is by antagonism of the cis-urocanic acid mediation of this form of immunosuppression.

Urocanic acid analogues and the suppression of the delayed type hypersensitivity response to Herpes simplex virus.

Ultraviolet irradiated urocanic acid (4-imidazoleacrylic acid) containing a mixture of cis- and trans-isomers has been shown previously to induce suppression of the delayed type hypersensitivity (DTH) response to Herpes simplex virus type 1 (HSV-1) in a murine model of infection. The cis-isomer of urocanic acid was prepared and the cis- and trans-isomers of 2-methylurocanic acid. 2-pyrroleacrylic acid, 2-furanacrylic acid, 2-thiopheneacrylic acid, 3-thiopheneacrylic acid as well as dihydrourocanic acid and histamine. Each was applied at concentrations of 1 and 50 micrograms per mouse to the shaved dorsal skin and the mice were infected subcutaneously with HSV 5 h later. After 8-10 days the DTH response to the virus was measured by an ear swelling test. It was found that cis-urocanic acid was effective in suppressing the DTH response at levels of 1 microgram per mouse or less. The cis- and trans-isomers of 2-furanacrylic acid, 2-pyrroleacrylic acid and 2-thiopheneacrylic acid were also effective, with the cis- form generally being more active than trans, and 2-pyrroleacrylic acid being particularly potent. Cis- and trans-3-thiopheneacrylic acid, on the other hand, were only marginally immunosuppressive while neither isomer of 2-methylurocanic acid had any suppressive ability. Dihydrourocanic acid and histamine were also shown to suppress the DTH response. Thus the structural features necessary for urocanic acid and its analogues to act as mediators of UV-induced immunosuppression could be deduced and implications for their mechanism of action discussed.

Two phenotypically distinct T cells are involved in ultraviolet-irradiated urocanic acid-induced suppression of the efferent delayed-type hypersensitivity response to herpes simplex virus, type 1 in vivo.

When UVB-irradiated urocanic acid, the putative photoreceptor/mediator for UVB suppression, is administered to mice it induces a dose-dependent suppression of the delayed-type hypersensitivity response to herpes simplex virus, type 1 (HSV-1), of similar magnitude to that induced by UV irradiation of mice. In this study, the efferent suppression of delayed-type hypersensitivity by UV-irradiated urocanic acid is demonstrated to be due to 2 phenotypically distinct T cells, (Thy1+, L3T4-, Ly2+) and (Thy1+, L3T4+, Ly2-). The suppression is specific for HSV-1. This situation parallels the generation of 2 distinct T-suppressor cells for HSV-1 by UV irradiation of mice and provides further evidence for the involvement of urocanic acid in the generation of UVB suppression.

[Biological activity of urocanic acid]. / Izuchenie biologicheskoi aktivnosti urokaninovoi kisloty.

Biological activity of urocanic acid was studied in a culture of CaOV cell in vitro and in mice with transferred tumors in vivo. Efficiency of urocanic acid in vitro was estimated by the rate of 3H-thymidine and 3H-uridine as well as 3H-lysine incorporation into cells, and in vivo by its influence on the tumor mass and on life duration of the tumor-bearing mice. Urocanic acid inhibited the protein synthesis in tumoral cells at the step of translation, retarding growth of various strains of transferring tumors in mice. The use of urocanic acid as an antitumoral drug is promising because the palliative effect obtained may be reinforced.