Avalia??o do estresse oxidativo e defesas antioxidantes na infec??o pelo Zika virus (Flaviviridae).

Programa de P?s-Gradua??o em Ci?ncias Biol?gicas. N?cleo de Pesquisas em Ci?ncias Biol?gicas, Pr?-Reitoria de Pesquisa de P?s Gradua??o, Universidade Federal de Ouro Preto.O Zika virus (ZIKV) ? um arbov?rus da fam?lia Flaviviridae, g?nero Flavivirus. A primeira epidemia do ZIKV no continente Americano foi reportada em 2015. Febre, exantema, artralgia, mialgia, cefaleia e conjutivite s?o alguns sintomas cl?ssicos da doen?a causada por esse v?rus. Entretanto, as epidemias mais atuais do ZIKV revelaram aspectos que at? ent?o n?o haviam sido relatados, como a microcefalia em beb?s e a s?ndrome de Guillian-Barr? em adultos. A emerg?ncia recente do ZIKV e sua associa??o com manifesta??es cl?nicas graves aumentaram a necessidade de mais estudos para elucidar a patog?nese do v?rus. Assim, compreender como o hospedeiro reage frente ?s infec??es virais ? de primordial import?ncia, pois pode auxiliar na maior compreens?o da patog?nese viral, bem como na busca por estrat?gias de controle e/ou preven??o da doen?a. Nesse sentido, na tentativa de conter a infec??o viral, muitas respostas do hospedeiro s?o elicitadas, dentre elas, a produ??o de esp?cies reativas de oxig?nio (ERO) que, dentre outras fun??es, atuam na defesa contra agentes infecciosos. No entanto, quando essas esp?cies est?o em excesso e n?o s?o efetivamente neutralizadas pelo sistema de defesa antioxidante, podem ocasionar danos ?s estruturas celulares, incluindo lip?deos, prote?nas e ?cidos nucl?icos, num evento conhecido como estresse oxidativo. Para muitas infec??es virais, incluindo infec??es por flaviv?rus, estudos t?m demonstrado que o estresse oxidativo ? fator importante na patog?nese viral. Entretanto, o papel do estresse oxidativo na patog?nese do ZIKV ainda precisa ser elucidado. Assim, o objetivo desse trabalho foi avaliar se a infec??o pelo ZIKV est? relacionada com o estresse oxidativo e com modula??o das vias antioxidantes celulares. Para tal, c?lulas neuronais U87-MG e hep?ticas HepG2, suscept?veis e permissivas ao ZIKV, foram infectadas e 15 e 24 horas p?s-infec??o (hpi) foram avaliados a produ??o de ERO, os n?veis dos biomarcadores de estresse oxidativo malondiald?ido (MDA) e prote?na carbonilada, a atividade das enzimas antioxidantes super?xido dismutase (SOD) e catalase (CAT) e a atividade do fator de transcri??o (eritr?ide-2)- fator 2 (Nrf2). A infec??o resultou, em ambas as linhagens celulares, num aumento significativo na produ??o de ERO e nos n?veis dos biomarcadores de estresse oxidativo. Ainda, foi observada uma diminui??o na atividade das enzimas antioxidantes SOD e CAT e uma diminui??o na ativa??o do fator de transcri??o Nrf2. Juntos, esses resultados mostram que a infec??o com o ZIKV in vitro resulta em um aumento na produ??o de ERO, estresse oxidativo e deple??o de enzimas antioxidantes via inibi??o da sinaliza??o de Nrf2. Em seguida, para verificar se a infec??o in vivo com o ZIKV tamb?m seria capaz de causar estresse oxidativo e alterar as defesas antioxidantes, foram avaliados os mesmos par?metros em c?rebro e f?gado de camundongos C57BL/6. Nos animais infectados 8 dias p?s-infec??o (dpi) foi observado no soro um aumento da atividade das transaminases hep?ticas aspartato e alanina aminotransferases (AST/ALT) e no f?gado e c?rebro foram observados aumento dos biomarcadores de estresse oxidativo e deple??o nas enzimas antioxidantes. Assim, nossos resultados mostram que a infec??o in vitro e in vivo pelo ZIKV leva a um aumento na produ??o de ERO, causa uma deple??o do sistema de defesa antioxidante, culminando com estresse oxidativo. Embora mais estudos sejam necess?rios para melhor compreender como e quanto o desbalan?o redox contribui para a patog?nese do ZIKV, os resultados aqui obtidos chamam aten??o para o car?ter consp?cuo do estresse oxidativo e deple??o das enzimas antioxidantes na infec??o pelo ZIKV, al?m de abrir prespectivas para futuras abordagens terap?uticas, especificamente ?quelas baseadas em compostos antioxidantes capazes de reverter o dano oxidativo.Zika virus (ZIKV) is an arbovirus that belongs to family Flaviviridae, genus Flavivirus. The first ZIKV epidemic in the American continent was reported in 2015. Fever, rash, arthralgia, myalgia, headache and conjunctivitis are some classic symptoms of the disease caused by this virus. However, the most current epidemics of ZIKV revealed aspects that had not been previously reported, such as microcephaly in babies and Guillian-Barr? syndrome in adults. The recent emergence of ZIKV and its association with severe clinical manifestations has increased the need for further studies to elucidate the pathogenesis of the virus. Thus, understanding how the host reacts to viral infections is very important since it can assist in a greater understanding of viral pathogenesis as well as in the search for strategies to control and / or prevent the disease. In this sense, to contain viral infection, many responses from the host are elicited, among them, the production of reactive oxygen species (ROS), which, among other functions, acts in defense against infectious agents. However, when these species are in excess and are not effectively neutralized by the antioxidant defense system, they can cause damage to cellular structures, including lipids, proteins and nucleic acids, in an event known as oxidative stress. For many viral infections, including flavivirus infections, studies have shown that oxidative stress is an important factor in viral pathogenesis. However, the role of oxidative stress in the pathogenesis of ZIKV has yet to be elucidated. Thus, the objective of this study was to assess whether ZIKV infection is related to oxidative stress and modulation in cellular antioxidant pathways. For this, neuronal U87-MG and hepatic HepG2 cells, susceptible and permissive to ZIKV, were infected and 15 and 24 hours post-infection (hpi) were evaluated the production of ROS, the levels of the biomarkers of oxidative stress malondialdehyde (MDA) and carbonyl protein, the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and the activity of the transcription factor (erythroid-2) - factor 2 (Nrf2). The infection resulted, in both cell lines, in a significant increase in the production of ROS and in the levels of oxidative stress biomarkers. In addition, a decrease in the activity of the antioxidant enzymes SOD and CAT and a decrease in the activation of the transcription factor Nrf2 was observed. Together, these results show that infection with ZIKV in vitro results in an increase in the production of ROS, oxidative stress and depletion of antioxidant enzymes via inhibition of Nrf2 signaling. Then, to verify whether infection with ZIKV would also be able to cause oxidative stress and alter antioxidant defenses in vivo, the same parameters were evaluated in the brain and liver of C57BL/6 mice. We observed in infected animals, an increase in the activity of liver transaminases in the serum. In the liver and brain an increase in the biomarkers of oxidative stress and depletion in antioxidant enzymes was observed. Thus, our results show that ZIKV infection in vitro and in vivo leads to an increase in ROS production causing a depletion of the antioxidant defense system, culminating in oxidative stress. Although more studies are needed to better understand how and how much the redox imbalance contributes to the pathogenesis of ZIKV, the results obtained here call attention to the conspicuous character of oxidative stress and depletion of antioxidant enzymes in ZIKV infection, in addition opening perspectives for future therapeutic approaches, specifically those based on antioxidant compounds capable of reversing oxidative damage

Implications of oxidative stress on viral pathogenesis.

Reactive species are frequently formed after viral infections. Antioxidant defences, including enzymatic and non-enzymatic components, protect against reactive species, but sometimes these defences are not completely adequate. An imbalance in the production of reactive species and the body?s inability to detoxify these reactive species is referred to as oxidative stress. The aim of this review is to analyse the role of oxidative stress in the pathogenesis of viral infections and highlight some major therapeutic approaches that have gained importance, with regards to controlling virus-induced oxidative injury. Attention will be focused on DNA viruses (papillomaviruses, hepadnaviruses), RNA viruses (flaviviruses, orthomyxoviruses, paramyxoviruses, togaviruses) and retroviruses (human immunodeficiency virus). In general, viruses cause an imbalance in the cellular redox environment, which depending on the virus and the cell can result in different responses, e.g. cell signaling, antioxidant defences, reactive species, and other processes. Therefore, the modulation of reactive species production and oxidative stress potentially represents a novel pharmacological approach for reducing the consequences of viral pathogenesis

Caraparu virus induces damage and alterations in antioxidant defenses in the liver of BALB/c mice after subcutaneous infection.

Oxidative stress is a disturbance in the oxidantantioxidant balance leading to potential cellular damage. Most cells can tolerate a mild degree of oxidative stress because they have a system that counteracts oxidation that includes antioxidant molecules such as glutathione (GSH) and superoxide dismutase (SOD). Disruption of the host antioxidant status has been recognized as an important contributor to the pathogenesis of many viruses. Caraparu virus (CARV) is a member of group C of the Bunyaviridae family of viruses. In South American countries, group C bunyaviruses are among the common agents of human febrile illness and have caused multiple notable outbreaks of human disease in recent decades; nevertheless, little is known about the pathogenic characteristics of these viruses. The purpose of this study was to examine the hepatic pathogenesis of CARV in mice and the involvement of oxidative stress and antioxidant defenses on this pathology. Following subcutaneous infection of BALB/c mice, CARV was detected in the liver, and histopathology revealed acute hepatitis. Increased serum levels of aspartate and alanine aminotransferases (AST/ALT) and greater hepatic expression of the proinflammatory cytokine tumor necrosis factor- a (TNF-a) were found in infected animals. CARV infection did not alter the biomarkers of oxidative stress but caused an increase in GSH content and altered the expression and activity of SOD. This is the first report of an alteration of oxidative homeostasis upon CARV infection, which may, in part, explain the hepatic pathogenesis of this virus, as well as the pathogenesis of other Bunyaviridae members

Oxidative stress in Mayaro virus infection.

Mayaro virus (MAYV) is a neglected tropical arbovirus that causes a febrile syndrome that is sometimes accompanied by incapacitating arthritis/arthralgia. The pathogenesis of MAYV has not been completely defined and oxidative stress mediated by an increase in reactive oxygen species (ROS) and/or depletion of antioxidant defences has been found to contribute to several aspects of viral disease. To investigate whether MAYV induced oxidative stress in host cells, we monitored ROS production, oxidative stress markers and antioxidant defences at different time points after infection. Our results show that MAYV induced significant oxidative stress in infected HepG2 cells, as indicated by the increase of malondialdehyde (MDA) and protein carbonyl levels, and by a significant decrease of the reduced versus oxidized glutathione (GSH/GSSG) ratio. Generally, MAYV-infected HepG2 cells also showed an increase in antioxidant defences. We observed an increase in the superoxide dismutase (SOD) and catalase (CAT) activities and the total glutathione content. To determine whether similar effects occurred in other cell types, we evaluated the ROS, MDA and SOD activity levels in J774 cells after MAYV infection. Similar to our observations in HepG2 cells, the J774 cells showed an increase in ROS, MDA and total SOD activity following MAYV infection. Thus, since the cellular redox environment is influenced by the production and removal of ROS, we hypothesize that the overproduction of ROS was responsible for the oxidative stress in response to the MAYV infection despite the increase in the antioxidant status. This study is the first report on the involvement of oxidative stress during MAYV infection. Collectively, our data shed light on some mechanisms that are operational in host cells following exposure to MAYV

Efects of a?ai on oxidative stress, ER stress, and infammationrelated parameters in mice with high fat diet-fed induced NAFLD.

Non-alcoholic fatty liver disease (NAFLD), the most predominant liver disease worldwide, is a progressive condition that encompasses a spectrum of disorders ranging from steatosis to steatohepatitis, and, ultimately, cirrhosis and hepatocellular carcinoma. Although the underlying mechanism is complex and multifactorial, several intracellular events leading to its progression have been identified, including oxidative stress, inflammation, mitochondrial dysfunction, apoptosis, and altered endoplasmic reticulum (ER) homeostasis. Phenolic compounds, such as those present in a?ai (Euterpe oleracea Mart.), are considered promising therapeutic agents due to their possible beneficial effects on the prevention and treatment of NAFLD. We tested in vitro effects of aqueous a?ai extract (AAE) in HepG2 cells and its influence on oxidative stress, endoplasmic reticulum stress, and inflammation in a murine model of high fat diet-induced NAFLD. In vitro AAE exhibited high antioxidant capacity, high potential to inhibit reactive oxygen species production, and no cytotoxicity. In vivo, AAE administration (3?g/kg) for six weeks attenuated liver damage (alanine aminotransferase levels), inflammatory process (number of inflammatory cells and serum TNF?), and oxidative stress, through the reduction of lipid peroxidation and carbonylation of proteins determined by OxyBlot and modulation of the antioxidant enzymes: glutathione reductase, SOD and catalase. No change was observed in collagen content indicating an absence of fibrosis, stress-related genes in RE, and protein expression of caspase-3, a marker of apoptosis. With these results, we provide evidence that a?ai exhibits hepatoprotective effects and may prevent the progression of liver damage related to NAFLD by targeting pathways involved in its progression

Antiviral activity of silymarin against Mayaro virus and protective effect in virus-induced oxidative stress.

Mayaro virus (MAYV) is a neglected arbovirus belonging to the family Togaviridae. Its infection leads to Mayaro fever, with clinical manifestations such as fever, myalgia, headache, rash, arthralgia, vomiting, and diarrhea. The most prominent complaint from infected person is the long-lasting arthritis/arthralgia. The treatment for Mayaro fever is mainly symptom-based and there are no vaccines or antiviral drugs currently available, thus, natural products with anti-MAYV activity may provide a potential alternative. Recent evidences suggest that oxidative stress plays an important role in MAYV infection and compounds capable of modulating oxidative stress could represent a novel therapeutic approach in modulating MAYV-associated oxidative cellular damage. Silymarin is a complex extracted of Silybum marianum, or milk thistle, and its major active compound is silybin, which has a remarkable biological effect. Its antioxidant and antiviral effects, including its antiviral activity against the Chikungunya virus (CHIKV), prompted us to think whether silymarin could also reduce the replication of the MAYV and restore the pro-oxidant/antioxidant balance in the context of MAYV infection, leading to reduced cellular oxidative stress. We assessed the antiviral activity and protective effect of silymarin against oxidative stress in MAYV-infected HepG2 cells. Cytopathic effect inhibition, viral replication, and plaque reduction assays were used to determine the anti-MAYV activity of silymarin. Additionally, we determined whether silymarin could reduce MAYV-induced oxidative cell damage. Briefly, silymarin exhibited potent antiviral activity against MAYV and reduced MAYV-induced ROS formation and levels of malondialdehyde (MDA) and carbonyl protein, which are biomarkers of oxidative stress. In conclusion, the ability of silymarin to inhibit MAYV replication and attenuate MAYV-induce oxidative stress warrants further investigation of this compound as a novel therapeutic approach to Mayaro fever disease

Mayaro virus induction of oxidative stress is associated with liver pathology in a non-lethal mouse model.

Mayaro virus (MAYV) causes Mayaro fever in humans, a self-limiting acute disease, with persistent arthralgia and arthritis. Although MAYV has a remerging potential, its pathogenic mechanisms remain unclear. Here, we characterized a model of MAYV infection in 3?4-week BALB/c mice. We investigated whether the liver acts as a site of viral replication and if the infection could cause histopathological alterations and an imbalance in redox homeostasis, culminating with oxidative stress. MAYV-infected mice revealed lower weight gain; however, the disease was self-resolving. High virus titre, neutralizing antibodies, and increased levels of aspartate and alanine aminotransferases were detected in the serum. Infectious viral particles were recovered in the liver of infected animals and the histological examination of liver tissues revealed significant increase in the inflammatory infiltrate. MAYV induced significant oxidative stress in the liver of infected animals, as well as a deregulation of enzymatic antioxidant components. Collectively, this is the first study to report that oxidative stress occurs in MAYV infection in vivo, and that it may be crucial in virus pathogenesis. Future studies are warranted to address the alternative therapeutic strategies for Mayaro fever, such as those based on antioxidant compounds