Tumor necrosis factor alpha has a crucial role in increased reactive oxygen species production in platelets of mice injected with lipopolysaccharide.

Increased reactive oxygen species (ROS) production leads to tissue damage observed in sepsis and lipopolysaccharide (LPS)-exposed animals. LPS stimulates cytokines releasing, including tumor necrosis factor alpha (TNF-α), that is important to ROS production. Platelets, considered inflammatory cells, generate ROS when exposed to LPS in vivo, but not when they are incubated in vitro with this compound. Therefore, we investigated the role of TNF-α on the increased intraplatelet ROS levels after LPS treatment. Mice were injected with LPS (1 mg/kg) or TNF-α (10 ng/kg), and blood was collected to prepare the washed platelets. Animals were treated with infliximab (anti-TNF-α antibody), R-7050 (non-selective TNF-α receptor antagonist) or apocynin (NADPH oxidase inhibitor). At 48 h after LPS or TNF-α injection, the ROS levels in ADP (25 µM)-activated platelets were evaluated by flow cytometry. Our data showed that injection of mice with LPS increased by 4-fold the ROS production (p < 0.05), which was significantly reduced by the treatments with infliximab, R-7050 or apocynin. Injection of mice with TNF-α markedly elevated the ROS formation in platelets (p < 0.05) that was reduced by infliximab, R-7050 or apocynin treatments. In separate experiments, platelets from saline-injected mice were incubated with TNF-α (30 to 3000 pg/mL) in absence or presence of infliximab, R-7050, apocynin or GKT137831 (NOX1/NOX4 inhibitor) before ROS measurements. TNF-α in vitro markedly increased the ROS levels, an effect significantly reduced by all treatments. Therefore, platelets are involved in the oxidative stress induced by LPS through TNF-α action, and NADPH oxidase takes part in this effect.

Discovery of phenylsulfonylfuroxan derivatives as gamma globin inducers by histone acetylation.

N-oxide derivatives 5(a-b), 8(a-b), and 11(a-c) were designed, synthesized and evaluated in vitro and in vivo as potential drugs that are able to ameliorate sickle cell disease (SCD) symptoms. All of the compounds demonstrated the capacity to releasing nitric oxide at different levels ranging from 0.8 to 30.1%, in vivo analgesic activity and ability to reduce TNF-α levels in the supernatants of monocyte cultures. The most active compound (8b) protected 50.1% against acetic acid-induced abdominal constrictions, while dipyrone, which was used as a control only protected 35%. Compounds 8a and 8b inhibited ADP-induced platelet aggregation by 84% and 76.1%, respectively. Both compounds increased γ-globin in K562 cells at 100 µM. The mechanisms involved in the γ-globin increase are related to the acetylation of histones H3 and H4 that is induced by these compounds. In vitro, the most promising compound (8b) was not cytotoxic, mutagenic and genotoxic.

Sepsis: The Involvement of Platelets and the Current Treatments.

OBJECTIVE: Sepsis, a serious and life threatening complication arising from infection caused by lipopolysaccharide, is a complex inflammatory syndrome, and one of the main causes of death in intensive care units (ICU). It is characterized as an over-response of pro-coagulant agents promotes coagulopathy and thrombus formation, resulting in disseminated intravascular coagulation (DIC). Furthermore, it can cause multiple organ dysfunction and hypotension (septic shock) resulting in death. Thrombocytopenia, which is a hallmark of sepsis, is strongly correlated as a negative marker of the infection. Additionally, platelets contribute with the oxidative stress in septic patients in order to exterminate the microbial pathogen. This review summarises the important role of platelets in the pathology of sepsis, and highlights potential treatment targets to improve the outcome of sceptic patients. METHODS: The search was performed in PubMed, books and retrieved journal articles for a period of three months. The figures were developed through Servier Medical Arts software. CONCLUSION: The exact treatment of sepsis is still the subject of considerable debate. Although here we presented several therapies that have shown promise for improving the outcome of patients, researching platelet function in sepsis has provided us targets to develop new medical approaches focusing specially on thrombocytopenia and DIC.

Antiplatelet and antithrombotic activities of non-steroidal anti-inflammatory drugs containing an N-acyl hydrazone subunit.

Nonsteroidal anti-inflammatory drugs (NSAIDs) 1-5 containing an N-acyl hydrazone subunit were prepared and their antiplatelet and antithrombotic activities assessed in vitro and in vivo. Compounds 1-5 inhibited the platelet aggregation induced by adenosine diphosphate and/or arachidonic acid, with inhibition rates of 18.0%-61.1% and 65.9%-87.3%, respectively. Compounds 1 and 5 were the most active compounds, inhibiting adenosine-diphosphate-induced platelet aggregation by 57.2% and 61.1%, respectively. The inhibitory rates for arachidonic-acid-induced platelet aggregation were similar for compound 2 (80.8%) and acetylsalicylic acid (ASA, 80%). After their oral administration to mice, compounds 1, 3, and 5 showed shorter mean bleeding times than ASA. Compounds 1 and 5 also protected against thromboembolic events, with survival rates of 40% and 33%, respectively, compared with 30% for ASA. In conclusion, these results indicate that these novel NSAIDs containing an NAH subunit may offer better antiplatelet and antithrombotic activities than ASA.

Reactive oxygen and nitrogen species modulate the ex-vivo effects of LPS on platelet adhesion to fibrinogen.

AIMS: Excessive production of nitric oxide (NO) and reactive oxygen species (ROS) in sepsis modulates different cell functions. Since the sepsis severity is associated with the degree of platelet activation, we decided to investigate the role of systemic generation of NO and ROS in modulating the platelet adhesion of lipopolysaccharide (LPS)-treated rats. MAIN METHODS: Platelet adhesion was evaluated using fibrinogen-coated 96-well microtiter plates. Cyclic GMP levels were measured using enzyme immunoassay kit. KEY FINDINGS: Treatment of rats with LPS significantly increased spontaneous platelet adhesion, but reduced the thrombin-activated platelet adhesion when compared with control rats. Chronic treatment of rats with the NO synthase inhibitor L-NAME (20 mg/rat/day, 7 days) prior to LPS injection normalized the increased adhesion in non-activated platelets, but failed to affect the adhesion in thrombin-activated platelets. The cGMP levels were modified neither in non-activated nor in thrombin-activated platelets of LPS-treated rats when compared with control rats. The incubation of non-activated platelets with the O2- scavenger PEG-SOD reversed the stimulatory effect of LPS on spontaneous adhesion, but had no effect in stimulated-platelet adhesion of non-treated or LPS-treated groups. Moreover, pretreatment of rats with the antioxidant N-acetylcysteine (NAC; 150 mg/kg) prevented the increase of non-activated platelet adhesion, and significantly reduced the inhibitory effect of LPS on thrombin-stimulated adhesion. SIGNIFICANCE: Our findings suggest that in LPS-treated rats, NO plays an important modulatory role only in non-stimulated platelet adhesion through cGMP-independent mechanisms, while ROS, directly or by affecting the redox state of the animals, modulates both non-activated and thrombin-activated platelet adhesion.