Hydrogen peroxide (HO) increases paracellular permeability of Madin-Darby canine kidney (MDCK) cells, but the mechanism mediating this effect remains unclear. Treatment of MDCK cells with HO activated ERK 1/2. Inhibition of ERK 1/2 activation blocked the ability of HO to increase paracellular permeability. Knockdown of zonula occludens-1 (ZO-1) protein but not occludin eliminated the ability of HO to increase paracellular permeability. HO treatment did not, however, affect the total cell content or contents of the Triton X-100-soluble and -insoluble fractions for occludin, ZO-1, or ZO-2. HO treatment decreased the number of F-actin stress fibers in the basal portion of the cells. Similar to wild-type MDCK cells, HO increased ERK 1/2 activation in ZO-1 knockdown and occludin knockdown cells. Inhibition of ERK 1/2 activation blocked the increase in paracellular permeability in occludin knockdown cells. ZO-1 knockdown cell paracellular permeability was regulated by PP1, an src inhibitor, indicating that the loss of response to HO was not a general loss of the ability to regulate the paracellular barrier. Inhibition of myosin ATPase activity with blebbistatin increased paracellular permeability in ZO-1 knockdown cells but not in wild-type MDCK cells. HO treatment sensitized wild-type MDCK cells to inhibition of myosin ATPase. Knockdown of TOCA-1 protein, which promotes formation of local branched actin networks, reproduced the effects of ZO-1 protein knockdown. These results demonstrate that HO increases MDCK cell paracellular permeability through activation of ERK 1/2. This HO action requires ZO-1 protein and TOCA-1 protein, suggesting involvement of the actin cytoskeleton.
Since the emergence of mRNA COVID-19 vaccines, various secondary cutaneous reactions have been reported. 1,2 Commonly observed cutaneous reactions include local injection-site erythema or discomfort, as well as urticarial and morbilliform eruptions. [1][2][3] Less frequent sequalae include perniosis, herpes simplex virus reactivation, flares of psoriasis, and pityriasis rosea-like reactions. 1,4 We report a 66-year-old female with hypertension, hypothyroidism, and hypercholesterolemia, who developed firm, tender, 4-5 cm deep-seated nodules on the right superior medial popliteal fossa and bilateral anterior tibia, 10 days after receiving the first dose of the COVID-19 Moderna mRNA-1273 vaccine (Figure 1). The patient provided informed consent to publish this case. By the time of medical evaluation, some nodules had begun to fade, and the patient was otherwise well, without symptoms of COVID-19 infection. The clinical impression was erythema nodosum (EN), and incisional biopsy of the nodule at the right superior medial popliteal fossa was performed 3 days later. One day prior to biopsy, COVID-19 PCR nasopharyngeal testing was negative. Histologic sections demonstrated widened subcutaneous septae containing an inflammatory infiltrate of lymphocytes, neutrophils, eosinophils, and histiocytes, compatible with EN. Routine hematologic and chemistry studies were unremarkable.Erythrocyte sedimentation rate, C-reactive protein, and circulating rheumatoid factor were normal. Anti-nuclear antibodies, anti-doublestranded DNA antibodies, anti-streptolysin antibodies, and hepatitis B
Melasma is often a difficult disease to treat, and can be psychologically distressing to patients. Currently, the gold standard for the treatment of melasma is hydroquinone. While this treatment has been used for many years, it does not come without risks with overuse. Chemical peels have also become an option for the treatment of melasma, but their efficacy and safety in comparison to hydroquinone has not yet been established. This review aims to investigate the various types, efficacy, and safety of chemical peels used to treat melasma.
Acne vulgaris is a chronic inflammatory skin condition caused by the blockage of sebaceous glands and colonization of Propionibacterium acnes. 1 While acne affects hundreds of thousands of individuals physically, it has been shown to increase one's risk of psychological disturbances including depression, anxiety, and low self-esteem. 2 One longitudinal study reported that even after 15 years, the probability of developing major depressive disorder among acne patients was 18.5%. 2 While several treatment options are available including
Psoriasis is a chronic inflammatory papulosquamous disorder which affects around 2% of the world’s population. A peak exacerbation in psoriatic symptoms was noted during COVID-19 due to lack of access to dermatological care mixed with heightened emotional stress during the pandemic. This case report describes a 52-year-old admitted male patient who sustained a diffuse rash on multiple areas of his body a week prior to testing positive for COVID-19. We explore plausible causes for the occurrence of the rash, discuss our treatment plan, include relevant clinical pictures, and review published literature to examine conditions that present similarly to the rash seen in our patient. It is crucial for dermatologists to be able to discern various systemic manifestations associated with cutaneous lesions, such as the one seen in this patient, in order to make an accurate and prompt diagnosis. A better understanding of the association between COVID-19 infection and psoriasiform lesions is needed for improving the prognostic and therapeutic outcomes in patients.
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