Abstract

APE1 is a multifunctional protein possessing DNA repair and redox activation of transcription factors. Blocking these functions leads to apoptosis, antiangiogenesis, cell-growth inhibition, and other effects, depending on which function is blocked. Because a selective inhibitor of the APE redox function has potential as a novel anticancer therapeutic, new analogues of E3330 were synthesized. Mass spectrometry was used to characterize the interactions of the analogues (RN8-51, 10-52, and 7-60) with APE1. RN10-52 and RN7-60 were found to react rapidly with APE1, forming covalent adducts, whereas RN8-51 reacted reversibly. Median inhibitory concentration (IC50 values of all three compounds were significantly lower than that of E3330. EMSA, transactivation assays, and endothelial tube growth-inhibition analysis demonstrated the specificity of E3330 and its analogues in blocking the APE1 redox function and demonstrated that the analogues had up to a sixfold greater effect than did E3330. Studies using cancer cell lines demonstrated that E3330 and one analogue, RN8-51, decreased the cell line growth with little apoptosis, whereas the third, RN7-60, caused a dramatic effect. RN8-51 shows particular promise for further anticancer therapeutic development. This progress in synthesizing and isolating biologically active novel E3330 analogues that effectively inhibit the APE1 redox function validates the utility of further translational anticancer therapeutic development. Antioxid. Redox Signal. 14, 1387–1401.

Accumulating evidence supports the importance of redox signaling in the pathogenesis and progression of hypertension. Redox signaling is implicated in many different physiological and pathological processes in the vasculature. High blood pressure is in part determined by elevated total peripheral vascular resistance, which is ascribed to dysregulation of vasomotor function and structural remodeling of blood vessels. Aberrant redox signaling, usually induced by excessive production of reactive oxygen species (ROS) and/or by decreases in antioxidant activity, can induce alteration of vascular function. ROS increase vascular tone by influencing the regulatory role of endothelium and by direct effects on the contractility of vascular smooth muscle. ROS contribute to vascular remodeling by influencing phenotype modulation of vascular smooth muscle cells, aberrant growth and death of vascular cells, cell migration, and extracellular matrix (ECM) reorganization. Thus, there are diverse roles of the vascular redox system in hypertension, suggesting that the complexity of redox signaling in distinct spatial spectrums should be considered for a better understanding of hypertension.

Abstract

Lipid rafts, the sphingolipid and cholesterol-enriched membrane microdomains, are able to form different membrane macrodomains or platforms upon stimulations, including redox signaling platforms, which serve as a critical signaling mechanism to mediate or regulate cellular activities or functions. In particular, this raft platform formation provides an important driving force for the assembling of NADPH oxidase subunits and the recruitment of other related receptors, effectors, and regulatory components, resulting, in turn, in the activation of NADPH oxidase and downstream redox regulation of cell functions. This comprehensive review attempts to summarize all basic and advanced information about the formation, regulation, and functions of lipid raft redox signaling platforms as well as their physiological and pathophysiological relevance. Several molecular mechanisms involving the formation of lipid raft redox signaling platforms and the related therapeutic strategies targeting them are discussed. It is hoped that all information and thoughts included in this review could provide more comprehensive insights into the understanding of lipid raft redox signaling, in particular, of their molecular mechanisms, spatial-temporal regulations, and physiological, pathophysiological relevances to human health and diseases. Antioxid. Redox Signal. 15, 1043–1083.

I. Introduction

II. Redox Signaling and Redox Injury

A. Redox signaling

B. Redox signaling versus injury

C. Common ROS as messengers

III. Concepts of LRs and Their Clustering

A. Concepts of LRs and existing debates

B. Molecular models of LRs

C. LRs on cell membranes

1. Caveolar LRs

2. Noncaveolar LRs

3. Ceramide-enriched micro- and macrodomains

D. Intracellular LRs

E. LR clusters or signaling platforms

IV. Redox Molecules Associated with LRs

A. The NADPH oxidase family

1. Structure of the NADHP oxidase family and their tissue distribution

2. Assembly and activation of NOX

3. Regulation of NOX activity

B. Superoxide dismutase

C. Catalase

D. Thioredoxin

E. Transient receptor protein C3 and C4: redox sensors

F. Effects of redox molecules on LRs

V. Frequently Used Methods for Identifying LR Redox Signaling Platforms

A. Fluorescent confocal microscopic imaging

B. Fluorescence resonance energy transfer

C. Membrane fraction flotation

D. Superoxide production in LR platforms

E. Others

VI. Downstream Targets of LR Redox Signaling

A. Signaling in phagocytic process

B. Transmembrane signaling via receptors in nonphagocytic cells

C. LR redox signaling not via receptors

D. Interactions of intracellular vesicles or organelles through LR redox signaling

E. Hypothetic models of LR redox signaling platforms

VII. Mechanisms Mediating the Formation of LR Redox Signaling Platforms

A. Ceramide metabolizing pathways

B. Association of ceramide metabolism and its signaling pathway

C. Role of ceramide-enriched microdomains in LRs clustering

D. Lysosome fusion and targeting of ASMase in LRs clustering

E. Cytoskeletal components and LR clustering

F. Feedforward amplifying mechanism

VIII. Physiology and Pathophysiology of LR Redox Signaling Platforms

A. Host defense and infection

B. Vascular inflammation and atherosclerosis

C. AD and neurological disease

D. Kidney diseases

E. Obesity

F. Tumors

IX. Possible Therapeutic Strategies Targeting LR Redox Signaling Platforms

A. Targeting cholesterol

B. Targeting ASMase activity

C. Targeting protein palmitoylation

X. Conclusions and Perspectives

Abstract

Accumulating evidence supports the importance of redox signaling in the pathogenesis and progression of hypertension. Redox signaling is implicated in many different physiological and pathological processes in the vasculature. High blood pressure is in part determined by elevated total peripheral vascular resistance, which is ascribed to dysregulation of vasomotor function and structural remodeling of blood vessels. Aberrant redox signaling, usually induced by excessive production of reactive oxygen species (ROS) and/or by decreases in antioxidant activity, can induce alteration of vascular function. ROS increase vascular tone by influencing the regulatory role of endothelium and by direct effects on the contractility of vascular smooth muscle. ROS contribute to vascular remodeling by influencing phenotype modulation of vascular smooth muscle cells, aberrant growth and death of vascular cells, cell migration, and extracellular matrix (ECM) reorganization. Thus, there are diverse roles of the vascular redox system in hypertension, suggesting that the complexity of redox signaling in distinct spatial spectrums should be considered for a better understanding of hypertension. Antioxid. Redox Signal. 10, 1045–1059.

Abstract

This is a non-peer-reviewed author-reported erratum addressing that Zyflamend sensitizes tumor cells to TRAIL-induced apoptosis through upregulation of death receptors and downregulation of survival proteins: role of reactive oxygen species-dependent CCAAT/enhancer-binding protein–homologous protein pathway. Kim JH, Park B, Gupta SC, Kannappan R, Sung B, and Aggarwal BB. Antioxid Redox Signal 16:413–427, 2012. The authors claim that Figure 7 reporting Western blot data was erroneous. Specifically, the β-actin panel of Fig. 7B was found to be switched with that of Fig. 7D. The corrected version is reported here. The authors claim that this correction does not influence the conclusion of the study.

Membrane (lipid) rafts and caveolae, a subset of rafts, are cellular domains that concentrate plasma membrane proteins and lipids involved in the regulation of cell function. In addition to providing signaling platforms for G-protein-coupled receptors and certain tyrosine kinase receptors, rafts/caveolae can influence redox signaling. This review discusses molecular characteristics of and methods to study rafts/caveolae, determinants that contribute to the localization of molecules in these entities, an overview of signaling molecules that show such localization, and the contribution of rafts/caveolae to redox signaling. Of particular note is the evidence that endothelial nitric oxide synthase (eNOS), NADPH oxygenase and heme oxygenase, along with other less well-studied redox systems, localize in rafts and caveolae. The precise basis for this localization and the contribution of raft/caveolae-localized redox components to physiology and disease are important issues for future studies.

Abstract

Membrane (lipid) rafts and caveolae, a subset of rafts, are cellular domains that concentrate plasma membrane proteins and lipids involved in the regulation of cell function. In addition to providing signaling platforms for G-protein-coupled receptors and certain tyrosine kinase receptors, rafts/caveolae can influence redox signaling. This review discusses molecular characteristics of and methods to study rafts/caveolae, determinants that contribute to the localization of molecules in these entities, an overview of signaling molecules that show such localization, and the contribution of rafts/caveolae to redox signaling. Of particular note is the evidence that endothelial nitric oxide synthase (eNOS), NADPH oxygenase, and heme oxygenase, along with other less well-studied redox systems, localize in rafts and caveolae. The precise basis for this localization and the contribution of raft/caveolae-localized redox components to physiology and disease are important issues for future studies. Antioxid. Redox Signal. 11, 1357–1372.

Abstract

Reactive oxygen species (ROS) are generated in response to growth factors, cytokines, G protein–coupled receptor agonists, or shear stress, and function as signaling molecules in nonphagocytes. However, it is poorly understood how freely diffusible ROS can activate specific signaling, so-called “redox signaling.” NADPH oxidases are a major source of ROS and now recognized to have specific subcellular localizations, and this targeting to specific compartments is required for localized ROS production. One important mechanism may involve the interaction of oxidase subunits with various targeting proteins localized in lamellipodial leading edge and focal adhesions/complexes. ROS are believed to inactivate protein tyrosine phosphatases, thereby establishing a positive-feedback system that promotes activation of specific redox signaling pathways involved in various functions. Additionally, ROS production may be localized through interactions of NADPH oxidase with signaling platforms associated with caveolae/lipid rafts, endosomes, and nucleus. These indicate that the specificity of ROS-mediated signal transduction may be modulated by the localization of Nox isoforms and their regulatory subunits within specific subcellular compartments. This review summarizes the recent progress on compartmentalization of redox signaling via activation of NADPH oxidase, which is implicated in cell biology and pathophysiologies. Antioxid. Redox Signal. 11, 1289–1299.

Abstract

Alcoholic and nonalcoholic fatty liver diseases are potentially pathological conditions that can progress to steatohepatitis, fibrosis, and cirrhosis. These conditions affect millions of people throughout the world in part through poor lifestyle choices of excess alcohol consumption, overnutrition, and lack of regular physical activity. Abnormal mitochondrial and cellular redox homeostasis has been documented in steatohepatitis and results in alterations of multiple redox-sensitive signaling cascades. Ultimately, these changes in signaling lead to altered enzyme function and transcriptional activities of proteins critical to mitochondrial and cellular function. In this article, we review the current hypotheses linking mitochondrial redox state to the overall pathophysiology of alcoholic and nonalcoholic steatohepatitis and briefly discuss the current therapeutic options under investigation. Antioxid. Redox Signal. 15, 485–504.

Abstract

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) have become recognized as second messengers for initiating and/or regulating vital cellular signaling pathways, and they are known also as deleterious mediators of cellular stress and cell death. ROS and RNS, and their cross products like peroxynitrite, react primarily with cysteine residues whose oxidative modification leads to functional alterations in the proteins. In this Forum, the collection of six review articles presents a perspective on the broad biological impact of cysteine modifications in health and disease from the molecular to the cellular and organismal levels, focusing in particular on reversible protein-S-glutathionylation and its central role in transducing redox signals as well as protecting proteins from irreversible cysteine oxidation. The Forum review articles consider the role of S-glutationylation in regulation of the peroxiredoxin enzymes, the special redox environment of the mitochondria, redox regulation pertinent to the function of the cardiovascular system, mechanisms of redox-activated apoptosis in the pulmonary system, and the role of glutathionylation in the initiation, propagation, and treatment of neurodegenerative diseases. Several common themes emerge from these reviews; notably, the probability of crosstalk between signaling/regulation mechanisms involving protein-S-nitrosylation and protein-S-glutathionylation, and the need for quantitative analysis of the relationship between specific cysteine modifications and corresponding functional changes in various cellular contexts. Antioxid. Redox Signal. 16, 471–475.

Abstract

Schizophrenia (SZ) is a brain disorder that has been intensively studied for over a century; yet, its etiology and multifactorial pathophysiology remain a puzzle. However, significant advances have been made in identifying numerous abnormalities in key biochemical systems. One among these is the antioxidant defense system (AODS) and redox signaling. This review summarizes the findings to date in human studies. The evidence can be broadly clustered into three major themes: perturbations in AODS, relationships between AODS alterations and other systems (i.e., membrane structure, immune function, and neurotransmission), and clinical implications. These domains of AODS have been examined in samples from both the central nervous system and peripheral tissues. Findings in patients with SZ include decreased nonenzymatic antioxidants, increased lipid peroxides and nitric oxides, and homeostatic imbalance of purine catabolism. Reductions of plasma antioxidant capacity are seen in patients with chronic illness as well as early in the course of SZ. Notably, these data indicate that many AODS alterations are independent of treatment effects. Moreover, there is burgeoning evidence indicating a link among oxidative stress, membrane defects, immune dysfunction, and multineurotransmitter pathologies in SZ. Finally, the body of evidence reviewed herein provides a theoretical rationale for the development of novel treatment approaches. Antioxid. Redox Signal. 15, 2011–2035.

Abstract

The development of alcoholic liver disease (ALD) is a complex process involving both parenchymal and nonparenchymal cells resident in the liver. Although the mechanisms for ALD are not completely understood, it is clear that increased oxidative stress, and activation of the innate immune system are essential elements in the pathophysiology of ALD. Oxidative stress from ethanol exposure results from increased generation of reactive oxygen species and decreased hepatocellular antioxidant activity, including changes in the thioredoxin/peroxiredoxin family of proteins. Both cellular and circulating components of the innate immune system are activated by exposure to ethanol. For example, ethanol exposure enhances toll-like receptor-4 (TLR-4)-dependent cytokine expression by Kupffer cells, likely due, at least in part, to dysregulation of redox signaling. Similarly, complement activation in response to ethanol leads to increased production of the anaphylatoxins, C3a and C5a, and activation C3a receptor and C5a receptor. Complement activation thus contributes to increased inflammatory cytokine production and can influence redox signaling. Here we will review recent progress in understanding the interactions between oxidative stress and innate immunity in ALD. These data illustrate that ethanol-induced oxidative stress and activation of the innate immune system interact dynamically during ethanol exposure, exacerbating ethanol-induced liver injury. Antioxid. Redox Signal. 15, 523–534.

The DNA base excision repair pathway is responsible for the repair of DNA damage caused by oxidation/alkylation and protects cells against the effects of endogenous and exogenous agents. Removal of the damaged base by creates a baseless (AP) site. AP endonuclease1 (Ape1) acts upon this site to continue the BER pathway repair. Failure to repair baseless sites leads to DNA strand breaks and cytotoxicity. In addition to Ape1's repair role, it also functions as a major redox signaling factor to reduce and activate transcription factors such as AP1, p53, HIF-1α and others which control the expression of genes important for cell survival and cancer promotion and progression. Thus the Ape1 protein interacts with proteins involved in DNA repair, growth signaling pathways and pathways involved in tumor promotion and progression. While knockdown studies using siRNA have been informative in studying the role of Ape1 in both normal and cancer cells, knocking down Ape1 does not reveal the individual role of Ape1's redox or repair functions. The identification of small molecule inhibitors of specific Ape1 functions is critical for mechanistic studies and translational applications. Here we discuss small molecule inhibition of Ape1 redox and its effect on both cancer and endothelial cells.

Abstract

The DNA base excision-repair pathway is responsible for the repair of DNA damage caused by oxidation/alkylation and protects cells against the effects of endogenous and exogenous agents. Removal of the damaged base creates a baseless (AP) site. AP endonuclease1 (Ape1) acts on this site to continue the BER-pathway repair. Failure to repair baseless sites leads to DNA strand breaks and cytotoxicity. In addition to the repair role of Ape1, it also functions as a major redox-signaling factor to reduce and activate transcription factors such as AP1, p53, HIF-1α, and others that control the expression of genes important for cell survival and cancer promotion and progression. Thus, the Ape1 protein interacts with proteins involved in DNA repair, growth-signaling pathways, and pathways involved in tumor promotion and progression. Although knockdown studies with siRNA have been informative in studying the role of Ape1 in both normal and cancer cells, knocking down Ape1 does not reveal the individual role of the redox or repair functions of Ape1. The identification of small-molecule inhibitors of specific Ape1 functions is critical for mechanistic studies and translational applications. Here we discuss small-molecule inhibition of Ape1 redox and its effect on both cancer and endothelial cells. Antioxid. Redox Signal. 10, 1853–1867.

It is well known for over hundred years that systemic blood vessels dilate to decreases in oxygen tension (hypoxia; low Po2) and this response appears to be critical to supply blood to the stressed organ. Conversely, pulmonary vessels constrict to a fall in alveolar Po2 in order to maintain a balance in ventilation-to-perfusion ratio. Currently, although there is little question that Po2 affects vascular reactivity and vascular smooth muscle cells (VSMC) act as oxygen sensors, the molecular mechanisms involved in modulating the vascular reactivity are still not clearly understood. Many laboratories including ours have suggested intracellular calcium concentration ([Ca2+]i), which regulates vasomotor function, is controlled by free radicals and redox signaling, including NAD(P)H and glutathione (GSH) redox. In this review article, therefore, we will discuss the implications of redox and oxidants alterations seen in pulmonary and systemic hypertension and how key targets that control [Ca2+]i such as ion channels, Ca2+ release from internal stores and uptake by the sarcoplasmic reticulum, and the Ca2+ sensitivity to the myofilaments, are regulated by changes in intracellular redox and oxidants associated with vascular Po2 sensing in physiological or pathophysiological conditions.

Abstract

It has been well known for >100 years that systemic blood vessels dilate in response to decreases in oxygen tension (hypoxia; low Po2), and this response appears to be critical to supply blood to the stressed organ. Conversely, pulmonary vessels constrict to a decrease in alveolar Po2 to maintain a balance in the ventilation-to-perfusion ratio. Currently, although little question exists that the Po2 affects vascular reactivity and vascular smooth muscle cells (VSMCs) act as oxygen sensors, the molecular mechanisms involved in modulating the vascular reactivity are still not clearly understood. Many laboratories, including ours, have suggested that the intracellular calcium concentration ([Ca2+ ]i), which regulates vasomotor function, is controlled by free radicals and redox signaling, including NAD(P)H and glutathione (GSH) redox. In this review article, therefore, we discuss the implications of redox and oxidant alterations seen in pulmonary and systemic hypertension, and how key targets that control [Ca2+ ]i, such as ion channels, Ca2+ release from internal stores and uptake by the sarcoplasmic reticulum, and the Ca2+ sensitivity to the myofilaments, are regulated by changes in intracellular redox and oxidants associated with vascular Po2 sensing in physiologic or pathophysiologic conditions. Antioxid. Redox Signal. 10, 1137–1152.

Abstract

Excessive reactive oxygen species Revised abstract, especially superoxide anion (O2•−), play important roles in the pathogenesis of many cardiovascular diseases, including hypertension and atherosclerosis. Superoxide dismutases (SODs) are the major antioxidant defense systems against O2•−, which consist of three isoforms of SOD in mammals: the cytoplasmic Cu/ZnSOD (SOD1), the mitochondrial MnSOD (SOD2), and the extracellular Cu/ZnSOD (SOD3), all of which require catalytic metal (Cu or Mn) for their activation. Recent evidence suggests that in each subcellular location, SODs catalyze the conversion of O2•− H2O2, which may participate in cell signaling. In addition, SODs play a critical role in inhibiting oxidative inactivation of nitric oxide, thereby preventing peroxynitrite formation and endothelial and mitochondrial dysfunction. The importance of each SOD isoform is further illustrated by studies from the use of genetically altered mice and viral-mediated gene transfer. Given the essential role of SODs in cardiovascular disease, the concept of antioxidant therapies, that is, reinforcement of endogenous antioxidant defenses to more effectively protect against oxidative stress, is of substantial interest. However, the clinical evidence remains controversial. In this review, we will update the role of each SOD in vascular biologies, physiologies, and pathophysiologies such as atherosclerosis, hypertension, and angiogenesis. Because of the importance of metal cofactors in the activity of SODs, we will also discuss how each SOD obtains catalytic metal in the active sites. Finally, we will discuss the development of future SOD-dependent therapeutic strategies. Antioxid. Redox Signal. 15, 1583–1606.

Abstract

Wall Shear Stress (WSS) has been identified as an important factor in the pathogenesis of atherosclerosis. We utilized a novel murine aortic coarctation model to acutely create a region of low magnitude oscillatory WSS in vivo. We employed this model to test the hypothesis that acute changes in WSS in vivo induce upregulation of inflammatory proteins, mediated by reactive oxygen species (ROS). Superoxide generation and VCAM-1 expression both increased in regions of low magnitude oscillatory WSS. WSS-dependent superoxide formation was attenuated by tempol treatment, but was unchanged in p47 phox knockout (ko) mice. However, in both the p47 phox ko mice and the tempol-treated mice, low magnitude oscillatory WSS produced an increase in VCAM-1 expression comparable to control mice. Additionally, this same VCAM-1 expression was observed in ebselen-treated mice and catalase overexpressing mice. These results suggest that although the redox state is important to the overall pathogenesis of atherosclerosis, the initial WSS-dependent inflammatory response leading to lesion localization is not dependent on ROS. Antioxid. Redox Signal. 15, 1369–1378.

Abstract

Epidemiological studies have shown that advancing age is associated with an increased prevalence of cardiovascular disease (CVD). Vascular smooth muscle cells (VSMC) comprise the major arterial cell population, and changes in VSMC behavior, function, and redox status with age contribute to alterations in vascular remodeling and cell signaling. Over two decades of work on aged animal models provide support for age-related changes in VSMC and/or arterial tissues. Enhanced production of reactive oxygen species (ROS) and insufficient removal by scavenging systems are hallmarks of vascular aging. VSMC proliferation and migration are core processes in vascular remodeling and influenced by growth factors and signaling networks. The intrinsic link between gene regulation and aging often relates directly to transcription factors and their regulatory actions. Modulation of growth factor signaling leads to up- or downregulation of transcription factors that control expression of genes associated with VSMC proliferation, inflammation, and ROS production. Four major signaling pathways related to the transcription factors, AP-1, NF-κB, FoxO, and Nrf2, will be reviewed. Knowledge of age-related changes in signaling pathways in VSMC that lead to alterations in cell behavior and function consistent with disease progression may help in efforts to attenuate age-related CVD, such as atherosclerosis. Antioxid. Redox Signal. 12, 641–655.

Abstract

Autophagy is a catabolic process through which damaged or long-lived proteins, macromolecules, or organelles are recycled by using lysosomal degradation machinery. Although the occurrence of autophagy in several cardiac diseases including ischemic or dilated cardiomyopathy, heart failure, hypertrophy, and during ischemia/reperfusion injury have been reported, the exact role of autophagy in these diseases is not known. Emerging studies indicate that oxidative stress in cellular system could induce autophagy, and oxidatively modified macromolecules and organelles can be selectively removed by autophagy. Mild oxidative stress–induced autophagy could provide the first line of protection against major damage like apoptosis and necrosis. Cardiac-specific loss of Atg5, an autophagic gene involved in the formation of autophagosome, causes cardiac hypertrophy, left ventricular dilation, and contractile dysfunction. Recently, it was revealed that Atg4, another autophagic gene involved in the formation of autophagosomes, is controlled through redox regulation under the condition of starvation-induced autophagy. In this review, we discuss the function of autophagy in association with oxidative stress and redox signaling in the remodeling of cardiac myocardium. Further research is needed to explore the possibilities of redox regulation of other autophagic genes and the role of redox signaling–mediated autophagy in the heart. Antioxid. Redox Signal. 11, 1975–1988.

Abstract

Generation of reactive oxygen species (ROS) by plasma membrane–localized NADPH oxidase (Nox 2) is a major mechanism of cell signaling associated with activation of the enzyme by a variety of agonists. With activation, the integral membrane flavocytochrome of Nox 2 transfers an electron from intracellular NADPH to extracellular O2, generating superoxide anion (O2•−). The latter dismutes to H2O2 which can diffuse through aquaporin channels in the plasma membrane to elicit an intracellular signaling response. O2•− also can initiate intracellular signaling by penetration of the cell membrane through anion channels (Cl- channel-3, ClC-3). Endosomes containing Nox2 and ClC-3 (called signaling endosomes) are composed of internalized plasma membrane and generate O2•− in the endosomal lumen to initiate signaling at intracellular sites. Thus, cellular signaling by Nox2 is dependent on the transmembrane flux of ROS. The role of this pathway has only recently been described and will require additional investigation to appreciate its physiological significance fully. Antioxid. Redox Signal. 11, 1349–1356.

The oxidation chemistry of thiols and disulfides of biologic relevance is described. The review focuses on the interaction and kinetics of hydrogen peroxide with low-molecular-weight thiols and protein thiols and, in particular, on sulfenic acid groups, which are recognized as key intermediates in several thiol oxidation processes. In particular, sulfenic and selenenic acids are formed during the catalytic cycle of peroxiredoxins and glutathione peroxidases, respectively. In turn, these enzymes are in close redox communication with the thioredoxin and glutathione systems, which are the major controllers of the thiol redox state. Oxidants formed in the cell originate from several different sources, but the major producers are NADPH oxidases and mitochondria. However, a different role of the oxygen species produced by these sources is apparent as oxidants derived from NADPH oxidase are involved mainly in signaling processes, whereas those produced by mitochondria induce cell death in pathways including also the thioredoxin system, presently considered an important target for cancer chemotherapy.

Abstract

The oxidation chemistry of thiols and disulfides of biologic relevance is described. The review focuses on the interaction and kinetics of hydrogen peroxide with low-molecular-weight thiols and protein thiols and, in particular, on sulfenic acid groups, which are recognized as key intermediates in several thiol oxidation processes. In particular, sulfenic and selenenic acids are formed during the catalytic cycle of peroxiredoxins and glutathione peroxidases, respectively. In turn, these enzymes are in close redox communication with the thioredoxin and glutathione systems, which are the major controllers of the thiol redox state. Oxidants formed in the cell originate from several different sources, but the major producers are NADPH oxidases and mitochondria. However, a different role of the oxygen species produced by these sources is apparent as oxidants derived from NADPH oxidase are involved mainly in signaling processes, whereas those produced by mitochondria induce cell death in pathways including also the thioredoxin system, presently considered an important target for cancer chemotherapy. Antioxid. Redox Signal. 10, 1549–1564.

Nitric oxide (NO) plays an important role in the regulation of cardiovascular function. S-nitrosylation, the covalent attachment of an NO moiety to sulfhydryl residues of proteins, resulting in the formation of S-nitrosothiols (SNOs), is a prevalent posttranslational protein modification involved in redox-based cellular signaling. Under physiologic conditions, protein S>-nitrosylation and SNOs provide protection preventing further cellular oxidative and nitrosative stress. However, oxidative stress and the resultant dysfunction of NO signaling have been implicated in the pathogenesis of cardiovascular diseases.

Previous reports have shown that the HIV regulatory protein Tat has both pro-oxidant and pro-inflammatory properties, suggesting that Tat might contribute to the neurological complications of HIV. However, the intracellular mechanisms whereby Tat triggers free radical production and inflammation, and the relationship between Tat-induced free radicals and inflammatory reactions, are still subject to debate. The present study was undertaken to evaluate the specific effects of Tat on NADPH oxidase in microglia and macrophages, and to determine the specific role of NADPH oxidase in Tat-induced cytokine/chemokine release and neurotoxicity. Application of Tat to microglia or macrophages caused dose-and time-dependent increases in superoxide formation that were prevented by both pharmacologic NADPH oxidase inhibitors and by specific decoy peptides (gp91ds). Furthermore, inhibition of NADPH oxidase attenuated Tat-induced release of IL-6 and TNFα, and MCP-1, and decreased microglial-mediated neurotoxicity. Finally, macrophages derived from NADPH oxidase deficient mice displayed reduced superoxide production, released lower levels of cytokines/chemokines, and induced less neurotoxicity in response to Tat compared to wild-type macrophages. Together, these data describe a specific and biologically significant signaling component of the macrophage/microglial response to Tat, and suggest the neuropathology associated with HIV infection might originate in part with Tat-induced activation of NADPH oxidase.