Rho-kinase as a novel gene therapeutic target in treatment of cold ischemia/reperfusion-induced acute lethal liver injury: effect on hepatocellular NADPH oxidase system

Disengaging the COVID-19 Clutch as a Discerning Eye Over the Inflammatory Circuit During SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the cytokine release syndrome (CRS) and leads to multiorgan dysfunction. Mitochondrial dynamics are fundamental to protect against environmental insults, but they are highly susceptible to viral infections. Defective mitochondria are potential sources of reactive oxygen species (ROS). Infection with SARS-CoV-2 damages mitochondria, alters autophagy, reduces nitric oxide (NO), and increases both nicotinamide adenine dinucleotide phosphate oxidases (NOX) and ROS. Patients with coronavirus disease 2019 (COVID-19) exhibited activated toll-like receptors (TLRs) and the Nucleotide-binding and oligomerization domain (NOD-), leucine-rich repeat (LRR-), pyrin domain-containing protein 3 (NLRP3) inflammasome. The activation of TLRs and NLRP3 by SARS-CoV-2 induces interleukin 6 (IL-6), IL-1β, IL-18, and lactate dehydrogenase (LDH). Herein, we outline the inflammatory circuit of COVID-19 and what occurs behind the scene, the interplay of NOX/ROS and their role in hypoxia and thrombosis, and the important role of ROS scavengers to reduce COVID-19-related inflammation.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

ROCK1 deficiency enhances protective effects of antioxidants against apoptosis and cell detachment

We have recently reported that the homologous Rho kinases, ROCK1 and ROCK2, play different roles in regulating stress-induced stress fiber disassembly and cell detachment, and the ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has remarkable anti-apoptotic, anti-detachment and pro-survival effects against doxorubicin, a chemotherapeutic drug. This study investigated the roles of ROCK isoforms in doxorubicin-induced reactive oxygen species (ROS) generation which is believed to be the major mechanism underlying its cytotoxicity to normal cells, and especially to cardiomyocytes. Different antioxidants have been shown to provide a protective role reported in numerous experimental studies, but clinical trials of antioxidant therapy showed insufficient benefit against the cardiac side effect. We found that both ROCK1-/- and ROCK2-/- MEFs exhibited reduced ROS production in response to doxorubicin treatment. Interestingly, only ROCK1 deficiency, but not ROCK2 deficiency, significantly enhanced the protective effects of antioxidants against doxorubicin-induced cytotoxicity. First, ROCK1 deficiency and N-acetylcysteine (an anti-oxidant) treatment synergistically reduced ROS levels, caspase activation and cell detachment. In addition, the reduction of ROS generation in ROCK1-/- MEFs in response to doxorubicin treatment was in part through inhibiting NADPH oxidase activity. Furthermore, ROCK1 deficiency enhanced the inhibitory effects of diphenyleneiodonium (an inhibitor of NADPH oxidase) on ROS generation and caspase 3 activation induced by doxorubicin. Finally, ROCK1 deficiency had greater protective effects than antioxidant treatment, especially on reducing actin cytoskeleton remodeling. ROCK1 deficiency not only reduced actomyosin contraction but also preserved central stress fiber stability, whereas antioxidant treatment only reduced actomyosin contraction without preserving central stress fibers. These results reveal a novel strategy to enhance the protective effect of antioxidant therapy by targeting the ROCK1 pathway to stabilize the actin cytoskeleton and boost the inhibitory effects on ROS production, apoptosis and cell detachment.

Current knowledge on oxidative stress in hepatic ischemia/reperfusion

Ischemia/reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, despite several attempts to solve the problem. The redox balance, which is pivotal for normal function and integrity of tissues, is dysregulated during I/R, leading to an accumulation of reactive oxygen species (ROS). Formation of ROS and oxidant stress are the disease mechanisms most commonly invoked in hepatic I/R injury. The present review examines published results regarding possible sources of ROS and their effects in the context of I/R injury. We also review the effect of oxidative stress on marginal livers, which are more vulnerable to I/R-induced oxidative stress. Strategies to improve the viability of marginal livers could reduce the risk of dysfunction after surgery and increase the number of organs suitable for transplantation. The review also considers the therapeutic strategies developed in recent years to reduce the oxidative stress induced by hepatic I/R, and we seek to explain why some of them have not been applied clinically. New antioxidant strategies that have yielded promising results for hepatic I/R injury are discussed.

Which NADPH oxidase isoform is relevant for ischemic stroke? The case for nox 2

Significance and Recent Advances: Ischemic stroke is the leading cause of disability and third in mortality in industrialized nations. Immediate restoration of cerebral blood flow is crucial to salvage brain tissue, but only few patients are eligible for recanalization therapy. Thus, the need for alternative neuroprotective strategies is huge, and antioxidant interventions have long been studied in this context. Reactive oxygen species (ROS) physiologically serve as signaling molecules, but excessive amounts of ROS, as generated during ischemia/reperfusion (I/R), contribute to tissue injury.

CRITICAL ISSUES

Nevertheless and despite a strong rational of ROS being a pharmacological target, all antioxidant interventions failed to improve functional outcome in human clinical trials. Antioxidants may interfere with physiological functions of ROS or do not reach the crucial target structures of ROS-induced injury effectively.

FUTURE DIRECTIONS

Thus, a potentially more promising approach is the inhibition of the source of disease-promoting ROS. Within recent years, NADPH oxidases (Nox) of the Nox family have been identified as mediators of neuronal pathology. As, however, several Nox homologs are expressed in neuronal tissue, and as many of the pharmacological inhibitors employed are rather unspecific, the concept of Nox as mediators of brain damage is far from being settled. In this review, we will discuss the contribution of Nox homologs to I/R injury at large as well as to neuronal damage in particular. We will illustrate that the current data provide evidence for Nox2 as the most important NADPH oxidase mediating cerebral injury.

Lack of association between the Thr431Asn and Arg83Lys polymorphisms of the ROCK2 gene and diabetic retinopathy

PURPOSE

To analyze the genotype distributions and allele frequencies for ROCK2 Thr431Asn and Arg83Lys polymorphisms among the diabetic retinopathy patients in a Turkish population.

METHODS

In this case-control study, 335 patients with diabetes mellitus were recruited and divided into three groups according to non-proliferative (n = 127), proliferative (n = 85) diabetic retinopathy, and no retinopathy (n = 123, served as a diabetic control group). Genomic DNA from the patients, and the nondiabetic healthy control cases (n = 132) was analyzed by real-time PCR using a Light-Cycler.

RESULTS

Neither genotype distributions nor the allele frequencies for the Thr431Asn or Arg83Lys polymorphisms showed a significant difference between the groups. The haplotypes were also not significantly associated with diabetic retinopathy.

CONCLUSION

These results suggest that there were no evidence for an association of ROCK2 gene Thr431Asn and Arg83Lys polymorphisms with diabetes or diabetic retinopathy in the Turkish population.

Toll-like receptors 2 and 4: initiators of non-septic inflammation in critical care medicine?

PURPOSE

Although the role of Toll-like receptors (TLRs) in bacterial infection and sepsis is well characterized, recent studies have also shown that TLR4 and TLR2 can play an important role in contributing to acute inflammatory processes and organ dysfunction in settings in which LPS or other bacterial products are not present. This review presents not only insights into pathophysiologic mechanisms that contribute to organ dysfunction and outcome in critical illness, but also direct therapeutic approaches to ameliorating such TLR-mediated responses that may potentially be of clinical benefit in critically ill patients.

METHOD

Literature review of the role of TLR4 and TLR2 in sterile inflammation relevant to critical care medicine using PubMed search, including original papers in English from 1990 to 2010.

CONCLUSION

There is increasing evidence that TLR4 and TLR2 are not only receptors for bacterial products, but also can be activated through other mechanisms relevant to the pathophysiology of critical illnesses. There is evidence that TLR4 and TLR2 are involved in ischemia-reperfusion injury and trauma where Gram-negative or Gram-positive bacteria are not detectible in the circulation or local organ sites, such as the lungs. In these settings TLRs can transduce other proinflammatory signals and thereby contribute to cellular activation leading to acute lung injury and other organ system dysfunction. The consequences of TLR4 and TLR2 activation through reactive oxygen species (ROS), heat shock proteins, and other non-LPS dependent mechanisms may be different from those associated with binding of the membrane component of bacteria to TLR4 or TLR2 and may produce different signatures of gene activation and release of proinflammatory mediators.

Effects of bone marrow stem cell transplantation on acute hepatic injury induced by carbon tetrachloride in rats

AIM: To observe the effects of bone marrow mesenchymal stem cells (BMSCs) on restoration of acute liver injury induced by carbon tetrachloride (CCl₄) in rats via RhoA-ROCK signaling pathway.

METHODS: BMSCs were isolated from male Sprague-Dawley (SD) rats, cultured and purified in a BMSCs culture system in vitro using their adherent characteristics. Rats were divided into 3 groups: normal control (N, n = 10), CCl₄ (C group for short hereafter, n = 10) and CCl₄ plus BMSCs (T group for short hereafter, n = 10). All the rats were sampled at the appointed time and various target markers were determined as follows: hematoxylin and eosin (HE) staining, as well as the index changes of liver's enzymology, were applied for evaluating the improvement of hepatic histological damage. The expression of RhoA mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR), and the expression of RhoA protein was assayed by Western blot.

RESULTS: In the T group, liver function of CCl₄-induced acute hepatic injury after BMSCs transplantation was improved markedly as compared with the C group (1 d, ALT: 89.70 ± 3.09 vs 147.59 ± 6.83; AST: 263.67 ± 17.05 vs 472.68 ± 19.04, P < 0.01 or 0.05; 7 d, ALT: 42.38 ± 14.31 vs 92.75 ± 6.70; AST: 173.85 ± 16.80 vs 260.41 ± 25.35, all P < 0.05), consistent with the improvement of hepatic histology. Little expression of RhoA was detected in the normal control group. In the C group, both mRNA and protein of RhoA were increased significantly as compared with normal control (1.39 ± 0.046 vs 0.57 ± 0.010, 1.23 ± 0.020 vs 0.35 ± 0.036, both P < 0.01), then was decreased slowly. In the T groups, the expression mRNA and protein of RhoA were obviously decreased, in concomitant with the restoration of liver histology and function, as compared with C group.

CONCLUSION: Rho-ROCK signaling pathways are involved in the process of acute hepatic injury in rats induced by CCl₄. BMSCs transplantation may accelerate the restoration of acute liver injury by inhibition of RhoA-ROCK signaling pathway.

Antioxidant enzyme gene transfer for ischemic diseases

The balance of redox is pivotal for normal function and integrity of tissues. Ischemic insults occur as results of a variety of conditions, leading to an accumulation of reactive oxygen species (ROS) and an imbalanced redox status in the tissues. The oxidant stress may activate signaling mechanisms provoking more toxic events, and eventually cause tissue damage. Therefore, treatments with antioxidants, free radical scavengers and their mimetics, as well as gene transfer approaches to overexpress antioxidant genes represent potential therapeutic options to correct the redox imbalance. Among them, antioxidant gene transfer may enhance the production of antioxidant scavengers, and has been employed to experimentally prevent or treat ischemic injury in cardiovascular, pulmonary, hepatic, intestinal, central nervous or other systems in animal models. With improvements in vector systems and delivery approaches, innovative antioxidant gene therapy has conferred better outcomes for myocardial infarction, reduced restenosis after coronary angioplasty, improved the quality and function of liver grafts, as well as outcome of intestinal and cerebral ischemic attacks. However, it is crucial to be mindful that like other therapeutic armentarium, the efficacy of antioxidant gene transfer requires extensive preclinical investigation before it can be used in patients, and that it may have unanticipated short- or long-term adverse effects. Thus, it is critical to balance between the therapeutic benefits and potential risks, to develop disease-specific antioxidant gene transfer strategies, to deliver the therapy with an optimal time window and in a safe manner. This review attempts to provide the rationale, the most effective approaches and the potential hurdles of available antioxidant gene transfer approaches for ischemic injury in various organs, as well as the possible directions of future preclinical and clinical investigations of this highly promising therapeutic modality.