SARS-CoV-2 infection, discovered and isolated in Wuhan City, Hubei Province, China, causes acute atypical respiratory symptoms and has led to profound changes in our lives. COVID-19 is characterized by a wide range of complications, which include pulmonary embolism, thromboembolism and arterial clot formation, arrhythmias, cardiomyopathy, multiorgan failure, and more. The disease has caused a worldwide pandemic, and despite various measures such as social distancing, various preventive strategies, and therapeutic approaches, and the creation of vaccines, the novel coronavirus infection (COVID-19) still hides many mysteries for the scientific community. Oxidative stress has been suggested to play an essential role in the pathogenesis of COVID-19, and determining free radical levels in patients with coronavirus infection may provide an insight into disease severity. The generation of abnormal levels of oxidants under a COVID-19-induced cytokine storm causes the irreversible oxidation of a wide range of macromolecules and subsequent damage to cells, tissues, and organs. Clinical studies have shown that oxidative stress initiates endothelial damage, which increases the risk of complications in COVID-19 and post-COVID-19 or long-COVID-19 cases. This review describes the role of oxidative stress and free radicals in the mediation of COVID-19-induced mitochondrial and endothelial dysfunction.

The present study aimed to investigate and compare biomarkers of oxidative stress and the activity of antioxidant enzymes in the plasma of patients with different stages of diabetic nephropathy. For this purpose, we studied (1) the levels of reactive oxygen species and reactive nitrogen species as oxidative stress parameters, (2) lipid and protein oxidation, (3) the activity of antioxidant enzymes, and (4) cytokine production. Patients with type 2 diabetes mellitus were divided into three groups according to the loss of renal function: patients with compensated diabetes mellitus with normal renal function DMT2N0 measured as an estimated glomerular filtration rate (eGFR) ≥ 90 mL/min/1.73 m², a group with decompensated diabetes mellitus with complication diabetic nephropathy and mild-to-moderate loss of renal function DMT2N1 (eGFR < 60 mL/min/1.73 m²: 59–45 mL/min/1.73 m²), and a decompensated diabetes mellitus with diabetic nephropathy group with moderate-to-severe loss of renal function DMT2N2 (eGFR > 30 mL/min/1.73 m²: 30–44 mL/min/1.73 m²). All results were compared with healthy volunteers. The results showed that patients with diabetic nephropathy had significantly higher levels of ROS, cytokine production, and end products of lipid and protein oxidation compared to healthy volunteers. Furthermore, patients with diabetic nephropathy had depleted levels of nitric oxide (NO), an impaired NO synthase (NOS) system, and reduced antioxidant enzyme activity (p < 0.05). These findings suggest that patients with impaired renal function are unable to compensate for oxidative stress. The decreased levels of NO radicals in patients with advanced renal complications may be attributed to damage NO availability in plasma. The study highlights the compromised oxidative status as a contributing factor to impaired renal function in patients with decompensated type 2 diabetes mellitus. The findings of this study have implications for understanding the pathogenesis of diabetic nephropathy and the role of oxidative stress and chronic inflammation in its development. The assessment of oxidative stress levels and inflammatory biomarkers may aid in the early detection and prediction of diabetic complications.

Oxidative stress is a critical factor in the onset of gestational diabetes and its associated complication, pre-eclampsia. This study aimed to evaluate (1) reactive oxygen species, reactive nitrogen species, and superoxide radical levels as indicators of oxidative stress, (2) lipid and protein oxidation, (3) antioxidant enzyme activity, and (4) cytokine production in pregnant women with gestational diabetes, as well as those with both gestational diabetes and pre-eclampsia, comparing these with biomarkers of gestational diabetes mellitus. The study categorized pregnant patients with gestational diabetes mellitus into two groups based on the presence of new-onset hypertension, measured twice every four hours, and a 24 h urine protein test showing 300 mg/day or ≥1+ proteinuria detected via a visual dipstick at ≥20 weeks of gestation. These groups were compared with normotensive pregnant patients. The findings revealed that patients with both gestational diabetes and pre-eclampsia exhibited significantly elevated levels of reactive oxygen species, cytokine production, and lipid and protein oxidation end products compared to normotensive pregnant women. Additionally, these patients showed reduced nitric oxide (•NO) levels, impaired NO synthase systems (eNOS and iNOS), and decreased antioxidant enzyme activities (p < 0.05). These results indicate that patients with gestational diabetes and pre-eclampsia are unable to counteract oxidative stress effectively. The study underscores the compromised oxidative status as a contributing factor to these complications. The findings provide insights into the pathogenesis of gestational diabetes and the subsequent pre-eclampsia, the role of oxidative stress, and the resulting complications. Measuring oxidative stress levels and inflammatory biomarkers could help in the early detection and prediction of gestational-diabetes-related complications in pregnant women.

Liver damage severity depends on both the dose and the exposure duration. Oxidative stress may increase the Ochratoxine-A (OTA) hepatotoxicity and many antioxidants may counteract toxic liver function. The present study aims to investigate the hepatoprotective potential of Azadirachta indicaA (A. indica; neem oil) seed oil to reduce acute oxidative disorders and residual OTA toxicity in a 28-day experimental model. The activity of antioxidant and hepatic enzymes, cytokines and the levels of oxidative stress biomarkers –MDA, GSPx, Hydroxiproline, GST, PCC, AGEs, PGC-1, and STIR-1 were analyzed by ELISA. The free radicals ROS and RNS levels were measured by EPR. The protective effects were studied in BALB/C mice treated with A. indica seed oil (170 mg/kg), alone and in combination with OTA (1.25 mg/kg), by gavage daily for 28 days. At the end of the experiment, mice treated with OTA showed changes in liver and antioxidant enzymes, and oxidative stress parameters in the liver and blood. A. indica oil significantly reduced oxidative stress and lipid peroxidation compared to the OTA group. In addition, the hepatic histological evaluation showed significant adipose tissue accumulation in OTA-treated tissues, while treatment with 170 mg/kg A. indica oil showed moderate adipose tissue accumulation.

This study investigates the association between diabetic retinopathy (DR) and its complication, diabetic macular edema (DME), and compared it with biomarkers of oxidative stress. This study aimed to compare the main indicators of the development of diabetic retinopathy measured as parameters of oxidative stress and compared to lipid oxidation, DNA damage, and cytokine levels and to monitor their quantitative manifestation in DME. This study evaluated 134 patients (62 males and 72 females; aged 62.10 ± 11.22 years) and divided them into two groups: type 2 diabetes mellitus with DR and type 2 diabetes mellitus with DME. All results were compared with healthy volunteers (n = 94) and showed that patients with DME had significantly higher levels of ROS, cytokine production, lipid oxidation, and DNA damage. In addition, patients with DME had decreased levels of nitric oxide (NO) and an impaired NO synthase (NOS) system (p < 0.05). These findings suggest that patients with DR and DME are unable to compensate for high levels of oxidative stress. Reduced NO levels in patients with DME may be due to impaired NO availability. This study highlights compromised oxidative status as a contributing factor to DME in patients with decompensated type 2 diabetes mellitus. An assessment of oxidative stress levels and inflammatory biomarkers may aid in the early detection and prediction of diabetic complications.

The present study aimed to investigate and compare oxidative stress biomarkers and antioxidant enzyme activity in the serum of women at risk of developing preeclampsia (PE) to prevent adverse pregnancy outcomes through early intervention. Changes in soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) levels were measured between 11 and 13 gestational weeks (gw.) before the onset of preeclampsia and its associated complications. This study evaluated the feasibility of the sFlt-1/PlGF biomarker ratio in predicting preeclampsia and adverse pregnancy outcomes, with the goal of preventive therapy with acetylsalicylic acid (150 mg daily), with acetylsalicylic acid (75 mg daily) and Clampsilin. For this purpose, the following were evaluated: (1) the levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) as parameters of oxidative stress; (2) lipid oxidation; (3) antioxidant enzyme activity; and (4) cytokine production. Analysis of the results showed that pregnant women at risk of preeclampsia had significantly higher levels of ROS, lipid oxidation, and superoxide anion radical (•O₂⁻) levels compared to normal pregnancies. In PE, depleted levels of nitric oxide (NO), impaired NO synthase system (NOS), and reduced antioxidant enzyme activity (p < 0.03) suggest that PE patients cannot compensate for oxidative stress (OS). In conclusion, oxidative stress in PE plays a key role, which arises from placental problems and affects both mother and baby. The groups with acetylsalicylic acid therapy (150 mg and 75 mg) were better affected compared to those on Clampsillin.