Differential correlations between changes to glutathione redox state, protein ubiquitination, and stress-inducible HSPA chaperone expression after different types of oxidative stress

Modulating Nitric Oxide: Implications for Cytotoxicity and Cytoprotection

Despite the significant progress in the fields of biology, physiology, molecular medicine, and pharmacology; the designation of the properties of nitrogen monoxide in the regulation of life-supporting functions of the organism; and numerous works devoted to this molecule, there are still many open questions in this field. It is widely accepted that nitric oxide (•NO) is a unique molecule that, despite its extremely simple structure, has a wide range of functions in the body, including the cardiovascular system, the central nervous system (CNS), reproduction, the endocrine system, respiration, digestion, etc. Here, we systematize the properties of •NO, contributing in conditions of physiological norms, as well as in various pathological processes, to the mechanisms of cytoprotection and cytodestruction. Current experimental and clinical studies are contradictory in describing the role of •NO in the pathogenesis of many diseases of the cardiovascular system and CNS. We describe the mechanisms of cytoprotective action of •NO associated with the regulation of the expression of antiapoptotic and chaperone proteins and the regulation of mitochondrial function. The most prominent mechanisms of cytodestruction-the initiation of nitrosative and oxidative stresses, the production of reactive oxygen and nitrogen species, and participation in apoptosis and mitosis. The role of •NO in the formation of endothelial and mitochondrial dysfunction is also considered. Moreover, we focus on the various ways of pharmacological modulation in the nitroxidergic system that allow for a decrease in the cytodestructive mechanisms of •NO and increase cytoprotective ones.

Hsp70 in Redox Homeostasis

Cellular redox homeostasis is precisely balanced by generation and elimination of reactive oxygen species (ROS). ROS are not only capable of causing oxidation of proteins, lipids and DNA to damage cells but can also act as signaling molecules to modulate transcription factors and epigenetic pathways that determine cell survival and death. Hsp70 proteins are central hubs for proteostasis and are important factors to ameliorate damage from different kinds of stress including oxidative stress. Hsp70 members often participate in different cellular signaling pathways via their clients and cochaperones. ROS can directly cause oxidative cysteine modifications of Hsp70 members to alter their structure and chaperone activity, resulting in changes in the interactions between Hsp70 and their clients or cochaperones, which can then transfer redox signals to Hsp70-related signaling pathways. On the other hand, ROS also activate some redox-related signaling pathways to indirectly modulate Hsp70 activity and expression. Post-translational modifications including phosphorylation together with elevated Hsp70 expression can expand the capacity of Hsp70 to deal with ROS-damaged proteins and support antioxidant enzymes. Knowledge about the response and role of Hsp70 in redox homeostasis will facilitate our understanding of the cellular knock-on effects of inhibitors targeting Hsp70 and the mechanisms of redox-related diseases and aging.

Imbalanced GSH/ROS and sequential cell death

Reactive oxygen species (ROS) are produced in cells during metabolic processes. Excessive intracellular ROS may react with large biomolecules, such as DNA, RNA, proteins, and small biomolecules, that is, glutathione (GSH) and unsaturated fatty acids. GSH has physiological functions, including free radical scavenging, anti-oxidation, and electrophile elimination. The disruption of ROS/GSH balance results in the deleterious oxidation and chemical modification of biomacromolecules, which eventually leads to cell-cycle arrest and proliferation inhibition, and even induces cell death. Imbalanced ROS/GSH may result from a direct increase of ROS, consumption of GSH, intracellular oxidoreductase interference, or thioredoxin activity reduction. Some chemicals including arsenic trioxide (ATO), pyrogallol (PG), and carbobenzoxy-Leu-Leu-leucinal (MG132) could also disrupt the balance of GSH and ROS. This article reviews the occurrence and consequences of the imbalance between GSH and ROS and introduces factors responsible for the disruption of cellular ROS and GSH balance, resulting in cell death. "GSH" and "ROS" were used as keywords to search the relevant literaturess.

Early Weaning Affects Liver Antioxidant Function in Piglets

Simple Summary

Early weaning is used to improve efficiency in pig production. However, early weaning may trigger liver oxidative stress in piglets. In this study, we evaluated the effects of early weaning on the development and antioxidant function of the liver in piglets. Our findings show that early weaning significantly decreases piglet body weight and suppresses liver development. We find that early weaning also suppresses the activities of superoxide dismutase (SOD) and catalase (CAT) (p < 0.05). It could be concluded that weaning may reduce the growth performance and liver antioxidant function of piglets.

Abstract

This study examined the impact of early weaning on antioxidant function in piglets. A total of 40 Duroc × Landrace × Large White, 21-day-old piglets (half male and half female) were divided into suckling groups (SG) and weaning groups (WG). Piglets in WG were weaned at the 21st day, while the piglets in SG continued to get breastfed. Eight piglets from each group were randomly selected and slaughtered at 24th-day (SG3, WG3) and 28th-day old (SG7, WG7). The body weight, liver index, hepatocyte morphology, antioxidant enzymes activity, gene expression of antioxidant enzymes, and Nrf2 signaling in the liver of piglets were measured. The results showed that weaning caused decreased body weight (p < 0.01), lower liver weight (p < 0.01), and decreased the liver organ index (p < 0.05) of piglets. The area and size of hepatocytes in the WG group was smaller than that in the SG group (p < 0.05). We also observed that weaning reduced the activity of superoxide dismutase (SOD) and catalase (CAT) (p < 0.05) in the liver of piglets. Relative to the SG3 group, the gene expression of GSH-Px in liver of WG3 was significantly reduced (p < 0.05). The gene expression of Nrf2 in the SG3 group was higher than that in the WG3 group (p < 0.01). The gene expression of NQO1 in the SG7 group was higher than that in the WG7 group (p < 0.05). In conclusion, weaning resulted in lower weight, slowed liver development, and reduced antioxidant enzymes activity, thereby impairing liver antioxidant function and suppressing piglet growth.