Citation: Klisic, A.; Bakic, M.; Karanikolic, V. Comparative Analysis of Redox Homeostasis Biomarkers in Patients with Psoriasis and Atopic Dermatitis. Antioxidants 2023, 12, 1875. https://doi.org/10.3390/ antiox12101875 Academic Editors: Kali Makedou and Michalis Aivaliotis Received: 8 September 2023 Revised: 8 October 2023 Accepted: 12 October 2023 Published: 18 October 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). antioxidants Article Comparative Analysis of Redox Homeostasis Biomarkers in Patients with Psoriasis and Atopic Dermatitis Aleksandra Klisic 1,2, * , Mirjana Bakic 3 and Vesna Karanikolic 4 1 Faculty of Medicine, University of Montenegro, 81000 Podgorica, Montenegro 2 Center for Laboratory Diagnostics, Primary Health Care Center, 81000 Podgorica, Montenegro 3 Clinic for Dermatovenerology, Clinical Center of Montenegro, 81000 Podgorica, Montenegro 4 Clinic for Skin Diseases of the Clinical Center Nis, School of Medicine, University of Nis, 18000 Nis, Serbia * Correspondence: aleksandranklisic@gmail.com Abstract: Abstract: AimThere are no studies regarding comparative analysis of serum biomarkers of oxidative stress in patients with psoriasis (PsO) and atopic dermatitis (AD). We aimed to compare the serum redox homeostasis parameters in patients with PsO vs. AD in an attempt to find the sensitive and specific oxidative stress biomarker that could best reflect the existence of one of these disease entities. Methods: Forty patients with PsO and forty patients with AD were consecutively included in this cross-sectional study. Parameters of redox homeostasis, i.e., pro-oxidants [malondialdehyde (MDA) and advanced oxidation protein products (AOPP)] and antioxidants [catalase (CAT) and superoxide dismutase (SOD)] were determined. Results: There was no difference in oxidative stress biomarkers between the PsO and AD group, except for higher CAT activity in the AD group (p < 0.001). Among all examined redox homeostasis biomarkers, ROC analysis showed that only CAT exhibited good diagnostic accuracy (AUC = 0.719) in the discrimination of patients with PsO vs. AD, with 0.436 U/L as the cut-off value of CAT activity. Conclusions: The CAT exhibited good diagnostic accuracy in the discrimination of patients with AD from those with PsO. The obtained results could suggest the importance of the use of antioxidants as a potential therapeutic strategy in the treatment of these two skin inflammatory diseases. Keywords: atopic dermatitis; inflammation; oxidative stress; psoriasis 1. Introduction Psoriasis (PsO) and atopic dermatitis (AD) are chronic diseases closely related to inflammation and oxidative stress [1]. Both diseases affect not only the skin but multiple organs due to their systemic nature [2]. The prevalence of AD varies from 10 to 30% in youngsters to up to 10% in the adult population. The prevalence of PsO in children is nearly 1.4%, whereas it ranges between 0.5 to 11.5% in adults [2,3]. The Th1-/Th17 immune response is assumed to be the key initiator of PsO develop- ment, whereas the Th2 immune response seems to be the major mechanism that triggers AD [2,4]. Despite these differences and despite the fact that the clinical manifestations of AD are being manifested in early childhood [5], these two disease entities have some similarities related to the increase in proinflammatory cytokines and enhanced pro-oxidant milieu [1,6–8], which lead to the destruction of proteins, DNA, and lipids by free radi- cals [7]. Namely, the abnormal epidermis differentiation/hyperproliferation is triggered by increased cytokines production (i.e., interleukin (IL)-12/23, IL-22, IL-17, tumor necrosis factor-alpha (TNF-α), IL-6, IL-4, IL-13, etc.)) that favor free radicals production, leading to diminishing already compromised non-enzymatic and enzymatic antioxidant system defense and creating a vicious circle between inflammation and redox imbalance in PsO and AD pathogenesis [1,9]. Antioxidants 2023, 12, 1875. https://doi.org/10.3390/antiox12101875 https://www.mdpi.com/journal/antioxidants