Para-Phenylenediamine (PPD) in commercially available Henna preparations in Bangladesh

In Bangladesh Henna is one of the most popular cosmetic products. The leaves of Henna are dried to make powder on which oil or water is mixed to get a paste to stain the body or hair. Although the occurance of contact allergic dermatitis in natural Henna is not so common, but this risk is increased by adding para-Phenylenediamine (PPD), which is used to make the Henna color dark to deep black. According to Scientific Committee on Consumer Products (SCCP), para-Phenylenediamine (PPD) is treated as an allergen and is considered as a very strong potential skin sensitizer. The presence of PPD in the commercially used tube Henna increases the risk of allergic contact dermatitis and several cases have already been reported worldwide. For this study, about 10 Henna samples were randomly collected from 10 selected areas of Dhaka city. The presence of PPD in Henna samples was determined by using High Performance Liquid Chromatography (HPLC). The result showed the presence of PPD in all of the Henna samples at substantial concentrations, ranging between 79.12-204.77 mg/kg where the average range is 142.36 mg/kg, which is much higher than the permissible levels (<2% or 0.1 mg/m3). The finding suggests that there should be a regulation and monitoring condition for the production and distribution of these adulterated Henna products in Bangladesh. Bioresearch Commu. 8(1): 1088-1092, 2022 (January)

Evaluation of the Skin-Sensitizing Potential of Brazilian Green Propolis

Propolis is a resinous mixture produced by bees from their secretions and plant material, so its composition varies depending on its botanical origin. Propolis has several beneficial bioactivities, but its skin sensitization properties have long been suspected. Nevertheless, the skin sensitization potency of Brazilian green propolis (BGP) has not been scientifically evaluated. Here, we used scientifically reliable tests to evaluate it. In vitro antigenicity test based on the human cell line activation test (OECD TG 442E) was performed by measuring the expression of CD54 and CD86, which are indicators of the antigenicity of test substances, on THP-1 and DC2.4 cells. BGP did not affect the expression of either marker on THP-1 cells, but upregulated the expression of CD86 on DC2.4 cells, suggesting that BGP may be a skin sensitizer. Then, we performed local lymph node assay (LLNA, OECD TG 429) as a definitive in vivo test. LLNA showed that 1.70% BGP primed skin sensitization and is a “moderate sensitizer”. Our results indicate scientific proof of the validity of arbitrary concentrations (1–2%), which have been used empirically, and provide the first scientific information on the safe use of BGP.

1,1,1,2,3,4,4,5,5,5-Decafluoropentane (HFC-4310mee)

HFC-43-10mee is a volatile liquid at room temperature and used as a cleaning agent, aerosol, etc. HFC-43-10mee has low acute inhalation toxicity; 4-hour LC50 in rats of approximately 11,000 ppm. The compound was not a skin or eye irritant and was not a skin sensitizer. A cardiac sensitization response was not observed at 5000 ppm. Inhalation exposure resulted in neurotoxicity consisting of tremors, convulsions, jerking, ataxia, abnormal gait, etc. at exposure concentrations of 2000 ppm and above. Within approximately 30 min of exposure the clinical signs appeared and resolved within 1–2 h during exposure; the rats appeared to adapt such that these clinical signs were no longer observed. The neurotoxicity observed was considered an acute response to HFC-43-10mee. In a 90-day study, rats exposed to 2000 ppm resulted in sporadic clinical signs of neurotoxicity. At 3500 ppm, the clinical signs were evident on most exposure days although as the study progressed the apparent incidence declined likely reflecting adaptation. The NOAEL was 500 ppm. Based on the occurrence of the clinical signs in this and other studies, an acute threshold for neurotoxicity was evident at approximately 2000 ppm and above. No developmental or reproductive toxicity were evident at 2000 ppm, although clinical signs of neurotoxicity occurred in maternal or parental rats at 2000 ppm. No effects on offspring were observed. HFC-43-10mee was not genotoxic in vitro or in vivo. Based on the data, the 8-h TWA WEEL value is 225 ppm (2320 mg/m3). The 15-min STEL is 700 ppm (7217 mg/m3).

Selective activation of TRPA1 ion channel by skin sensitizer nitrobenzene DNFB

BACKGROUND AND PURPOSE: Chemical 2, 4-dinitrofluorobenzene (DNFB), commonly called as Sanger’s reagent, is well known as skin sensitizer to cause dermatitis. However, how the DNFB causes skin inflammation remains unknown. In this study we aimed at identifying the molecular target that DNFB acts on. EXPERIMENTAL APPROACH: We used a fluorescent calcium imaging plate reader as an initial screening assay and patch-clamp recordings for validation. Molecular docking in combination with site-directed mutagenesis was carried out to investigate DNFB binding sites in TRPA1 ion channel. KEY RESULTS: We found the chemical DNFB that selectively activates TRPA1 channel with EC50 of 2.36 ± 0.26 µM. Single-channel recording reveals that DNFB increases the channel open probability and acts on three residues C621, Y658 and E625 critical for DNFB-mediated TRPA1 activation. CONCLUSION AND IMPLICATIONS: Our findings not only explain a molecular mechanism underlying the dermatitis and pruritus caused by chemical DNFB, but also provides a molecular tool that is 7.5-time more potent than current AITC molecule and can be used for elucidating TRPA1 channel pharmacology and pathology.

Identification of Potential Skin Sensitizers in Myrrh

The exudate of Commiphora myrrha (myrrh) has been known for centuries as one of the most popular natural skin remedies. The characterization and safety assessment of myrrh ingredients are challenging due to the chemical variability of commercially available sources, as well as potential adulteration. Human and animal data have reported potential concerns about myrrh as a skin sensitizer, although no specific chemical entity has been identified as a potential culprit yet. In the present work, the in chemico high-throughput method using dansylated cysteamine (HTS-DCYA) was applied to extract and fractions of myrrh samples in an attempt to identify potential skin sensitizers. Nine oxo-furanogermacranes and the sesquiterpenoid alismol were isolated as major constituents. Five of the compounds were identified as weakly to moderately reactive in HTS-DCYA and could therefore trigger the molecular initiating event leading to skin sensitization. The reactive compounds were identified as 6-oxofuranodienones (2 and 5) and methoxyfuranogermacrenones (7 and 9). The reaction adducts of 2 with DCYA was confirmed by HPLC-DAD-MS and by HPLC-MS/MS experiments. A comparison of the chemical profile of myrrh samples available in-house confirmed a certain degree of chemical variability, with compounds 1, 7, and 9 occurring in four of the six samples.