Distinct Species-Specific and Toxigenic Metabolic Profiles for 6PPD and 6PPD Quinone by P450 Enzymes: Insights from In Vitro and In Silico Studies.

The tire rubber antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its quinone product (6PPDQ) are prevalent emerging contaminants, yet their biotransformation profiles remain poorly understood, hampering the assessment of environmental and health risks. This study investigated the phase-I metabolism of 6PPD and 6PPDQ across aquatic and mammalian species through in vitro liver microsome (LM) incubations and in silico simulations. A total of 40 metabolites from seven pathways were identified using the highly sensitive nano-electrospray ionization mass spectrometry. Notably, 6PPDQ was consistently detected as a 6PPD metabolite with an approximate 2% yield, highlighting biotransformation as a neglected indirect exposure pathway for 6PPDQ in organisms. 6PPDQ was calculated to form through a facile two-step phenyl hydroxylation of 6PPD, catalyzed by cytochrome P450 enzymes. Distinct species-specific metabolic kinetics were observed, with fish LM demonstrating retarded biotransformation rates for 6PPD and 6PPDQ compared to mammalian LM, suggesting the vulnerability of aquatic vertebrates to these contaminants. Intriguingly, two novel coupled metabolites were identified for 6PPD, which were predicted to exhibit elevated toxicity compared to 6PPDQ and result from C-N oxidative coupling by P450s. These unveiled metabolic profiles offer valuable insights for the risk assessment of 6PPD and 6PPDQ, which may inform future studies and regulatory actions.

Tissue Accumulation and Biotransformation of 6PPD-Quinone in Adult Zebrafish and Its Effects on the Intestinal Microbial Community.

The pronounced lethality of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-quinone or 6PPDQ) toward specific salmonids, while sparing other fish species, has received considerable attention. However, the underlying cause of this species-specific toxicity remains unresolved. This study explored 6PPDQ toxicokinetics and intestinal microbiota composition in adult zebrafish during a 14-day exposure to environmentally realistic concentrations, followed by a 7-day recovery phase. Predominant accumulation occurred in the brain, intestine, and eyes, with the lowest levels in the liver. Six metabolites were found to undergo hydroxylation, with two additionally undergoing O-sulfonation. Semiquantitative analyses revealed that the predominant metabolite featured a hydroxy group situated on the phenyl ring adjacent to the quinone. This was further validated by assessing enzyme activity and determining in silico binding interactions. Notably, the binding affinity between 6PPDQ and zebrafish phase I and II enzymes exceeded that with the corresponding coho salmon enzymes by 1.04-1.53 times, suggesting a higher potential for 6PPDQ detoxification in tolerant species. Whole-genome sequencing revealed significant increases in the genera Nocardioides and Rhodococcus after exposure to 6PPDQ. Functional annotation and pathway enrichment analyses predicted that these two genera would be responsible for the biodegradation and metabolism of xenobiotics. These findings offer crucial data for comprehending 6PPDQ-induced species-specific toxicity.

A Dual-Signal Sensing for the Visual and Luminescent Detection of p-Phenylenediamine Based on Cerium-Nitrogen-Co-Doped Carbon Dots.

Herein, a visual and luminescent dual-mode (colorimetric and fluorometric) method for the detection of P-phenylenediamine (PPD) in hair dye was successfully established based on cerium-nitrogen co-doped carbon dots (Ce, N-CDs) that displayed remarkable luminescence and peroxidase activity. Ce, N-CDs catalyzed H2O2 to produce superoxide anion, which then oxidized the colorless 3,3,5,5-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB), capable of quenching the fluorescence through fluorescence resonance energy transfer (FRET) between Ce, N-CDs and oxTMB. The reducing properties of PPD could reduce oxTMB back to TMB, leading to a decrease in the absorption intensity of oxTMB and a fluorescence recovery of Ce, N-CDs. As a result, the quantitative detection of PPD could be achieved by measuring the absorption values of oxTMB and the fluorescence signal of Ce, N-CDs. The detection limits for PPD were calculated as 0.36 µM and 0.10 µM for colorimetry and fluorimetry, respectively. Furthermore, smartphone application (ColorPicker) capable of measuring the RGB value of the color was utilized in the detection system, facilitating on-site quantitative detection. This approach effectively shortens the detection time and simplifies the operation, offering a powerful and convenient tool for real-time monitoring of PPD.

Need for new strategies to improve the recall and avoidance rates of contact allergens: A retrospective cohort study from Turkey.

BACKGROUND: Previous studies reported a low-to-moderate benefit from patch testing regarding allergen recall and avoidance. OBJECTIVES: To determine the allergen recall and avoidance rates of patients with allergic contact dermatitis (ACD) in Turkey. METHODS: This was a retrospective cohort study based on a phone questionnaire of 465 patients diagnosed with ACD from major allergen groups, that is, metals, preservatives, rubber, fragrances (ubiquitous allergens) and hair dye/black henna, topical drug and resins (nonubiquitous allergens), at our tertiary referral centre between 1996 and 2018. RESULTS: Among 176 responders, allergen groups were remembered better (53.4%) than the individual allergens (36.9%). Age <40 years and keeping the allergy pass had a significantly positive impact on the recall rate of methylchloroisothiazolinone/methylisothiazolinone and nickel, particularly non-occupational nickel allergy from metal jewellery in females, respectively. Exacerbations of ACD (56.3%) were mainly due to reexposures to ubiquitous allergens. 42.9% of patients with occupational ACD changed or quit their job, most of them being construction workers and hairdressers, showing a high share (83.3%) of benefit. CONCLUSIONS: The overall rates of allergen recall and avoidance were moderate. New strategies are needed to improve the recall and avoidance rates of contact allergens, such as increased use of allergy pass, smartphone applications and legal precautions.

Construction of a Colorimetric and Fluorescence Dual-Mode Immunoassay Detection of Alpha-Hemolysin in Milk.

Alpha-hemolysin (Hla) is a major virulence factor secreted by Staphylococcus aureus (S. aureus), which can lyse a variety of mammalian cells and help bacteria evade the host immune system or antibiotics, posing a safety hazard to human health. Therefore, it is critical to establish a quick-responsive and sensitive method for Hla detection to ensure food safety. In this work, a dual-mode immunoassay was developed with both colorimetric and fluorescent readouts for discriminative detection of Hla. The proposed sensing system consists of p-phenylenediamine (PPD) and fluorescein, where fluorescein functions as a fluorescent reporter, and PPD serves a dual function as a colorimetric reporter and fluorescence quencher. Subsequently, the reaction system of this method was optimized, and the detection limit, sensitivity, and specificity were evaluated. Under optimal conditions, the proposed method possesses excellent analytical performance in the range from 0.5 to 500 ng/mL with a limit of detection as low as 0.5 ng/mL. Noteworthy, this method was successfully employed for the detection of Hla in milk with good selectivity and high accuracy. Overall, the dual-mode immunoassay provides a superior platform for the on-site, quantitative, and accurate detection of Hla in food samples.

Fluorescent and colorimetric dual-mode detection of Cu2+ based on carbon dots.

A fluorescent and colorimetric dual-mode strategy based on carbon dots (CDs) was rationally designed for sensitive determination of Cu2+. Green fluorescent CDs with high absolute quantum yield of 72.9% were synthesized by facile one-step hydrothermal treatment of triethylenetetramine and Rose Bengal. Cu2+ could trigger the oxidative and chromogenic reaction of p-phenylenediamine (PPD) to generate chromogenic PPDox, accompanied by the fluorescence quenching of the CDs. The quenching mechanism was identified as the inner filter effect between PPDox and CDs. Therefore, a colorimetric/fluorescent dual-mode detection method for Cu2+ recognition was constructed. The limits of detection for Cu2+ were 4.14 µM and 1.28 µM for colorimetric and fluorescent mode, respectively. In addition, this method had achieved satisfactory results in the detection of Cu2+ in real serum samples.

Ratiometric fluorescence probe based on carbon dots and p-phenylenediamine-derived nanoparticles for the sensitive detection of manganese ions.

A ratiometric fluorescence probe based on carbon quantum dots with 420 nm emission (bCQDs) and a p-phenylenediamine-derived fluorescence probe with 550 nm emission (yprobe) is constructed for the detection of Mn2+. The presence of Mn2+ results in the enhanced absorption band at 400 nm of yprobe, and the fluorescence of yprobe is significantly enhanced based on the chelation-enhanced fluorescence mechanism. The fluorescence of bCQDs is then quenched based on the inner filtration effect. The ratio (I550/I420) linearly increases with the increase of Mn2+ concentration within 2.00 × 10-7-1.50 × 10-6 M, and the limit of detection is 1.76 × 10-9 M. Given the fluorescence color changing from blue to yellow, the visual sensing of Mn2+ is feasible based on bCQDs/yprobe coupled with RGB value analysis. The practicability of the proposed method has been verified in tap water, lake water, and sparkling water beverage, indicating that bCQDs/yprobe has promising application in Mn2+ monitoring.

Presentations to emergency departments in Melbourne, Australia diagnosed as allergic contact dermatitis.

BACKGROUND: This study investigated cases diagnosed as allergic contact dermatitis (ACD) in emergency departments (EDs) and management. METHODS: A multisite retrospective study of patients attending EDs in metropolitan Melbourne between July 2017 and June 2018 was performed. Using International Statistical Classification of Disease-10 (ICD-10) codes, the Victorian Agency for Health Information generated a list of cases of contact dermatitis (CD). Demographic and clinical data were analysed. RESULTS: Two hundred twenty-eighty patients from 14 different sites were diagnosed with ACD. Hair dyes caused the most cases, and one such case was admitted to hospital. It was apparent from the specified causes that cases of irritant CD were misdiagnosed as ACD. There were significant differences in management with dermatology input, with dermatologists more often advising oral corticosteroids (33.3% vs. 14.5%, P = 0.004) topical corticosteroids (92.9% vs. 38.7%, P < 0.01), emollients (38.1% vs. 20.4%, P = 0.01) and less often advising antihistamines (16.7% vs. 44.6%, P < 0.001). With dermatology input, potent or very potent steroids were more likely to be prescribed (69.3% vs. 11.1%, P < 0.001); without, a mild potency steroid was more likely to be prescribed (63.9% vs. 4%, P = 0.01). CONCLUSION: Improved understanding, diagnosis and management of CD are needed in EDs.

Participation of Lattice Oxygen in Perovskite Oxide as a Highly Sensitive Sensor for p-Phenylenediamine Detection.

The harmful effects on the human body from p-phenylenediamine (PPD) in hair dyes can cause allergies and even cancer. Therefore, it is particularly important to accurately control and detect the content of PPD in our daily products and environment. Here, a small amount of non-metallic elemental P doped in perovskite oxide of SrCoO3-δ (SC) forms a good catalytic material, SrCo0.95P0.05O3-δ (SCP), for PPD detection. The improved performance compared with that of the parent SC can be attributed to three contributing factors, including a larger amount of highly oxidative oxygen species O22-/O-, better electrical conductivity, and more active sites on the P5+-oxygen bonds of SCP. Moreover, the lattice oxygen mechanism (LOM) with highly active species of lattice O vacancies and adsorbed -OO for electrocatalytic oxidation of PPD by the SCP/GCE (glass carbon electrode) sensor is proposed in our work. More importantly, the SCP/GCE sensor exhibits good stability, a low limit of detection, and high reliability (error < 5.78%) towards PPD determination in real samples of hair dyes, suggesting the substantial research potential for practical applications.

A Novel Spectrophotometric Method for Determination of Percarbonate by Using N, N-Diethyl-P-Phenylenediamine as an Indicator and Its Application in Activated Percarbonate Degradation of Ibuprofen.

Sodium percarbonate (SPC) concentration can be determined spectrophotometrically by using N, N-diethyl-p-phenylenediamine (DPD) as an indicator for the first time. The ultraviolet-visible spectrophotometry absorbance of DPD•+ measured at 551 nm was used to indicate SPC concentration. The method had good linearity (R2 = 0.9995) under the optimized experimental conditions (pH value = 3.50, DPD = 4 mM, Fe2+ = 0.5 mM, and t = 4 min) when the concentration of SPC was in the range of 0-50 µM. The blank spiked recovery of SPC was 95-105%. The detection limit and quantitative limit were 0.7-1.0 µM and 2.5-3.3 µM, respectively. The absorbance values of DPD•+ remained stable within 4-20 min. The method was tolerant to natural water matrix and low concentration of hydroxylamine (<0.8 mM). The reaction stoichiometric efficiency of SPC-based advanced oxidation processes in the degradation of ibuprofen was assessed by the utilization rate of SPC. The DPD and the wastewater from the reaction were non-toxic to Escherichia coli. Therefore, the novel Fe2+/SPC-DPD spectrophotometry proposed in this work can be used for accurate and safe measurement of SPC in water.

Computational mechanistic studies on persulfate assisted p-phenylenediamine polymerization.

p-Phenylenediamine (p-PDA) is a monomer of many important polymers such as kevlar, twaron, poly-p-PDA. Most of the noticed polymers formation is initiated by a free-radical, but their polymerization mechanism is not elucidated computationally. The proposed study helps to fully understand the frequently utilized initiator/oxidant, potassium persulfate (K2 S2 O8 ) role in the aromatic diamines polymerization, which support experimental protocols, and a polymer scope. The formation of the poly-p-PDA is studied with the density functional theory (DFT) B3LYP-D3 functional using experimental polymerization parameters (0°C and aqueous media). K2 S2 O8 initiated free-radical polymerization of p-PDA is studied in detail, taking into account sulfate free-radical (SO4 - )· , SFR, persulfate anion (S2 O8 )2- , PA and K2 S2 O8 cluster, PP. The reaction mechanism is calculated as the conversion of p-PDA to free-radical, the p-PDA free-radical attack to the next p-PDA (dimerization), ammonia extrusion from the dimer adduct, the dimer adduct conversion to the free-radical (completion of p-PDA polymerization cycle) for the polymer chain elongation. Calculations show that the dimerization step is the rate-limiting step with a 29.2 kcal/mol energy barrier when SFR initiates polymerization. In contrast, the PA-assisted dimerization energy barrier is only 12.7 kcal/mol. PP supported polymerization is calculated to have very shallow energy barriers completing the polymerization cycle, i.e., dimerization (TS2K, ∆G‡  = 11.6 kcal/mol) and ammonia extrusion (TS3K, ∆G‡  = 6.7 kcal/mol).

Fabrication of graphene oxide-p-phenylenediamine nanocomposites as fluorescent chemosensors for detection of metal ions.

In this work, graphene oxide-p-Phenylenediamine nanocomposites of two different ratios of Graphene oxide: p-Phenylenediamine (1:1 and 1:5) were prepared and characterized by using analytical, spectroscopic and microscopic studies (GO-pPD 11 and GO-pPD 15). These nanocomposites were employed as fluorescent chemosensors for sensing potential cations. Remarkably, graphene oxide-p-Phenylenediamine nanocomposites of ratio 1:1 (GO-pPD 15) was selective and sensitive to Ag+ ions, whereas the graphene oxide-p-Phenylenediamine nanocomposites of ratio 1:5 (GO-pPD 15) was selective to Ce3+ions. A possible mechanism as switch "off-on" is proposed built on the inhibition of the photo induced electron transfer process in both the fluorescent probes in detecting the metal ions. In addition, interference studies were performed with the help of competitive complexation analysis and no significant interference were found by other potentially competing cations. The pH studies revealed that both the chemosensors can be used at the physiological pH for the ion detection and also the detection time was within 2-3 min. Both the chemosensors show good reversibility and hence the sensors can be used for multiple times. The newer nanocomposites were then utilized in the real water sample analysis as to check its real level application purpose.

Ratiometric electrochemical sensing platform based on N-doped MOF-derived CoNi/C for the determination of p-phenylenediamine in hair dyes.

A stable ratiometric electrochemical sensing platform is introduced for the determination of p-phenylenediamine (PPD). Specifically, the proposed sensing platform employs nitrogen-doped MOF pyrolysis-derived CoNi/C (N-CoNi/C) which was deployed as the sensing agent and methylene blue (MB) as the internal reference, and the MB combined with N-CoNi/C nanomaterials by a simple immersion adsorption process. Full characterization of N-CoNi/C was carried out with respect to morphology, composition, and electrochemical behavior, and the sensing performance of the ratiometric electrochemical sensing platform was evaluated. Complete separation of the oxidation peaks of PPD and MB was achieved using the MB/N-CoNi/C composite modified glassy carbon electrode (MB/N-CoNi/C/GCE) and their ratio signals were used for quantitative determination of PPD. The electrical signal was linearly related to the concentration of PPD in the concentration range 0.3-100 µM, with a fitted correlation coefficient of 0.9987 and a detection limit of 0.091 µM (S/N = 3). Additionally, the sensor has been successfully used for the determination of PPD in commercial hair dyes with a recovery rate of over 95%.

Fabrication of Orange Fluorescent Boron-Doped Graphene Quantum Dots for Al3+ Ion Detection.

Aluminum is a kind of metal that we often encounter. It can also be absorbed by the human body invisibly and will affect our bodies to a certain extent, e.g., by causing symptoms associated with Alzheimer's disease. Therefore, the detection of aluminum is particularly important. The methods to detect metal ions include precipitation methods and electrochemical methods, which are cumbersome and costly. Fluorescence detection is a fast and sensitive method with a low cost and non-toxicity. Traditional fluorescent nanomaterials have a high cost, high toxicity, and cause harm to the human body. Graphene quantum dots are a new type of fluorescent nanomaterials with a low cost and non-toxicity that can compensate for the defects of traditional fluorescent nanomaterials. In this paper, c-GQDs and o-GQDs with good performance were prepared by a bottom-up hydrothermal method using o-phenylenediamine as a precursor and citric acid or boric acid as modulators. They have very good optical properties: o-GQDs exhibit orange fluorescence under UV irradiation, while c-GQDs exhibits cyan fluorescence. Then, different metal ions were used for ion detection, and it was found that Al3+ had a good quenching effect on the fluorescence of the o-GQDs. The reason for this phenomenon may be related to the strong binding of Al3+ ions to the N and O functional groups of the o-GQDs and the rapid chelation kinetics. During the chelation process, the separation of o-GQDs' photoexcited electron hole pairs leads to their rapid electron transfer to Al3+, in turn leading to the occurrence of a fluorescence-quenching phenomenon. In addition, there was a good linear relationship between the concentration of the Al3+ ions and the fluorescence intensity, and the correlation coefficient of the linear regression equation was 0.9937. This illustrates the potential for the wide application of GQDs in sensing systems, while also demonstrating that Al3+ sensors can be used to detect Al3+ ions.

A novel synergistic effect of TiO2 and ZnO incorporation in PES-based thin-film nanocomposite nanofiltration membrane for treatment of textile wastewater.

A novel synergistic effect of TiO2 and ZnO incorporation in the PES-based thin-film nanocomposite nanofiltration membranes was developed for the treatment of common effluent treatment plant (CETP) textile wastewater. PES@TiO2 membranes were developed by phase inversion via the immersion precipitation method followed by the addition of zinc oxide nanoparticles prepared by the rapid microwave-assisted hydrothermal process via interfacial polymerization. p-Phenylenediamine was used as a monomer for the IP process that was coated on the PES@TiO2 support layer. Various techniques have been applied to characterize the developed thin-film nanocomposite membranes such as Fourier transform infrared (FTIR) microscopy, field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), and contact angle measurement to examine the presence of vibrational modes, surface morphology, the crystal structure of nanoparticles, and hydrophilicity of the membrane, respectively. Membrane properties include porosity, salt rejection, mean pore radius, pure water flux, and industrial effluent rejection efficiency that were studied. The thin-film nanocomposite membrane T5-PES@TiO2(2%)-ZnO(0.3%) was prepared with a combination of 17 wt% PES, 78 wt% DMF, 3 wt% PVP K30, 2% TiO2, 2.5 wt% PPD, 0.3 wt% ZnO, and 1.0 wt% TMC that exhibited high water permeability, porosity, higher industrial effluent rejection, and salt rejection efficiency compared to the neat PES membrane.

Scalp involvement in patients referred for patch testing: Retrospective cross-sectional analysis of North American Contact Dermatitis Group data, 1996 to 2016.

BACKGROUND: Scalp conditions are often multifactorial. OBJECTIVE: To characterize patients with scalp involvement and patch-testing outcomes. METHODS: Retrospective cross-sectional analysis of North American Contact Dermatitis Group data (1996-2016). Study groups included patients with scalp involvement (≤3 anatomic sites coded) with or without additional sites. RESULTS: A total of 4.8% of patients (2331/48,753) had scalp identified as 1 of up to 3 affected anatomic sites. Approximately one-third of "scalp-only" individuals had a specific primary diagnosis of allergic contact dermatitis (38.6%), followed by seborrheic dermatitis (17.2%) and irritant contact dermatitis (9.3%). When adjacent anatomic sites were affected, allergic contact dermatitis was more frequently identified as the primary diagnosis (>50%). The top 5 currently clinically relevant allergens in scalp-only patients were p-phenylenediamine, fragrance mix I, nickel sulfate, balsam of Peru, and cinnamic aldehyde. Methylisothiazolinone sensitivity was notable when adjacent anatomic sites were involved. The top 3 specifically identified sources for scalp-only allergens were hair dyes, shampoo/conditioners, and consumer items (eg, hair appliances, glasses). LIMITATIONS: Tertiary referral population. CONCLUSION: Isolated scalp involvement was less likely to be associated with allergic contact dermatitis than when adjacent anatomic sites were involved. Overlap with multiple diagnoses was frequent, including seborrheic dermatitis, irritant dermatitis, other dermatoses, or all 3. p-Phenylenediamine was the most common allergen.

Exposure to N-monoacetyl-p-phenylenediamine impaired ovarian function in mice.

p-Phenylenediamine (PPD) is the main constituent of permanent hair dye and is also widely used in the photographic and rubber industries. PPD and its metabolites have been shown to increase the risk of cancer (especially ovarian cancer); however, their effect on female reproduction is unclear. We investigated the effects of the PPD metabolite N-monoacetyl-PPD (MAPPD) on mouse blastocyst development and ovarian function. Sixty 8-week-old female Kunming mice were administered at 0-, 100-, and 300-mg/kg/day MPPD by gavage for 28 days. KGN (human ovarian granulosa cells) were treated with MAPPD at concentrations of 0, 50, 100, and 300 µg/ml for 48 h. The number of abnormal blastocysts increased on gestation day 3.5 in all treatment groups. Compared with the control group, in MAPPD exposed group, the number of antral follicles decreased, the levels of E2 and P4 decreased in ovarian tissue, the serum levels of E2 , P4 , luteinizing hormone (LH), and T decreased, and follicle-stimulating hormone (FSH) increased. The expression of FSH receptor (FSHR) and LH receptor (LHR) was significantly downregulated, and the level of oxidative stress was significantly increased. In KGN cells, the level of reactive oxygen species increased in a dose-dependent manner, and the mRNA levels of FSHR, LHR, and aromatase increased. These results suggest that MAPPD inhibits FSH- and LH-induced aromatase activity by causing oxidative stress, which decrease hormone levels, leading to abnormal follicle development. Meanwhile, MAPPD exposure could affect early embryonic development abnormalities by affecting the quality of ovum.

The expression pattern of N-acetyltransferase 1 in healthy human skin.

BACKGROUND: N-acetyltransferase 1 (NAT1) is an enzyme expressed among others in keratinocytes in human skin. NAT1 is important in the biotransformation of aromatic amines, an important example being p-phenylenediamine (PPD), a hair dye molecule. Unoxidized PPD penetrates the skin and is N-acetylated by NAT1. OBJECTIVES: To investigate in detail the expression pattern of NAT1 in human skin. MATERIALS AND METHODS: Cryosections obtained from healthy human skin were stained for NAT1 and expression patterns were observed. NAT1 double stainings were performed with antibodies against different cellular organelles to determine expression patterns. RESULT: A speckled, granular expression of NAT1 was seen predominantly in the stratum basale. NAT1 was expressed in a cytoplasmic pattern, perinuclear, and in the nucleus. No co-localisation was seen with the selected cellular organelles. Local differences in NAT1 expression patterns were observed between donors and between different biopsies obtained from the same donor. CONCLUSIONS: NAT1 is expressed predominantly in the stratum basale and can be found in the cytoplasm, nucleus, and perinuclear in human skin. Further studies should be performed to investigate expression of NAT1 in a larger sample size.

Patch-test results in terms of the recently recommended allergens in children and adolescents: A retrospective cohort study over 22 years from Turkey.

BACKGROUND: A European pediatric patch-test series was suggested recently. OBJECTIVES: To evaluate the patch-test results in children (<10-years-old) and adolescents (10- to 18-years-old) in Turkey, focusing on the clinical/occupational relevance and the diagnostic value of the recently suggested series. PATIENTS AND METHODS: A retrospective cohort study on 317 consecutively patch-tested patients ≤18 years of age, between 1996 and 2017. RESULTS: The contact sensitization rate was 46.1%. Allergic contact dermatitis (ACD) was diagnosed in 30.9%, comprising non-occupational (84.7%) and occupational (15.3%) ACD. Nickel was the leading allergen in almost every age group. Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) was the clinically most relevant allergen, followed by p-phenylenediamine (PPD), ammonium persulfate, fragrance mix I, nickel sulfate, and mercury/mercury(II)amidochloride. Occupational ACD was most frequently seen in hairdresser apprentices (adolescents only) who were sensitized with PPD ± ammonium persulfate. ACD from MCI/MI increased to 5-fold, ammonium persulfate and mercurial compounds to 2-fold, and PPD to 1.7-fold after 2007. Almost one third of patients would be missed by testing only with the recommended allergens. CONCLUSIONS: For patch testing in Turkish children and adolescents, we suggest additionally testing with ammonium persulfate, mercury/mercury(II)amidochloride, toluenesulfonamide formaldehyde resin, and polyethylene glycol, the latter as a marker for nitrofurazone allergy, in appropriate patients.

Skin barrier damage after exposure to paraphenylenediamine.

BACKGROUND: p-Phenylenediamine (PPD) is a strong contact allergen used in hair dye that is known to cause allergic contact dermatitis (ACD). Both private and occupational exposure to PPD is frequent, but the effect of PPD exposure in nonallergic occupationally exposed subjects is unknown. OBJECTIVE: We sought to investigate the effects of PPD exposure on the skin of occupationally exposed subjects with and without clinical symptoms. METHODS: Skin biopsy specimens were collected from 4 patients with mild and 5 patients with severe PPD-related ACD and 7 hairdressers without contact dermatitis on day 4 after patch testing with 1% PPD in petrolatum. RNA sequencing and transcriptomics analyses were performed and confirmed by using quantitative RT-PCR. Protein expression was analyzed in skin from 4 hairdressers and 1 patient with ACD by using immunofluorescence staining. Reconstructed human epidermis was used to test the effects of PPD in vitro. RESULTS: RNA sequencing demonstrated downregulation of tight junction and stratum corneum proteins in the skin of patients with severe ACD after PPD exposure. Claudin-1 (CLDN-1), CLDN8, CLDN11, CXADR-like membrane protein (CLMP), occludin (OCLN), membrane-associated guanylate kinase inverted 1 (MAGI1), and MAGI2 mRNA expression was downregulated in patients with severe ACD. CLDN1 and CLMP expression were downregulated in nonresponding hairdressers and patients with mild ACD. Filaggrin 1 (FLG1), FLG2, and loricrin (LOR) expression were downregulated in patients with ACD. Confocal microscopic images showed downregulation of CLDN-1, FLG-1, and FLG-2 expression. In contrast, 3-dimensional skin cultures showed upregulation of FLG-1 in response to PPD but downregulation of FLG-2. CONCLUSION: PPD-exposed skin is associated with extensive transcriptomic changes, including downregulation of tight junction and stratum corneum proteins, even in the absence of clinical symptoms.