Group V Phospholipase A2 Mediates Endothelial Dysfunction and Acute Lung Injury Caused by Methicillin-Resistant Staphylococcus Aureus

Lung endothelial dysfunction is a key feature of acute lung injury (ALI) and clinical acute respiratory distress syndrome (ARDS). Previous studies have identified the lipid-generating enzyme, group V phospholipase A2 (gVPLA2), as a mediator of lung endothelial barrier disruption and inflammation. The current study aimed to determine the role of gVPLA2 in mediating lung endothelial responses to methicillin-resistant Staphylococcus aureus (MRSA, USA300 strain), a major cause of ALI/ARDS. In vitro studies assessed the effects of gVPLA2 inhibition on lung endothelial cell (EC) permeability after exposure to heat-killed (HK) MRSA. In vivo studies assessed the effects of intratracheal live or HK-MRSA on multiple indices of ALI in wild-type (WT) and gVPLA2-deficient (KO) mice. In vitro, HK-MRSA increased gVPLA2 expression and permeability in human lung EC. Inhibition of gVPLA2 with either the PLA2 inhibitor, LY311727, or with a specific monoclonal antibody, attenuated the barrier disruption caused by HK-MRSA. LY311727 also reduced HK-MRSA-induced permeability in mouse lung EC isolated from WT but not gVPLA2-KO mice. In vivo, live MRSA caused significantly less ALI in gVPLA2 KO mice compared to WT, findings confirmed by intravital microscopy assessment in HK-MRSA-treated mice. After targeted delivery of gVPLA2 plasmid to lung endothelium using ACE antibody-conjugated liposomes, MRSA-induced ALI was significantly increased in gVPLA2-KO mice, indicating that lung endothelial expression of gVPLA2 is critical in vivo. In summary, these results demonstrate an important role for gVPLA2 in mediating MRSA-induced lung EC permeability and ALI. Thus, gVPLA2 may represent a novel therapeutic target in ALI/ARDS caused by bacterial infection.

Secretory Phospholipase A2 Enzymes in Acute Lung Injury

The secretory phospholipase A₂ (sPLA₂) group of secreted enzymes hydrolyze phospholipids and lead to the production of multiple biologically active lipid mediators. sPLA₂s and their products (e.g., eicosanoids) play a significant role in the pathophysiology of various inflammatory diseases, including life-threatening lung disorders such as acute lung injury (ALI) and the Acute Respiratory Distress Syndrome (ARDS). The ALI/ARDS spectrum of severe inflammatory conditions is caused by direct (such as bacterial or viral pneumonia) or indirect insults (sepsis) that are associated with high morbidity and mortality. Several sPLA₂ isoforms are upregulated in patients with ARDS as well as in multiple ALI preclinical models, and individual sPLA₂s exert unique roles in regulating ALI pathophysiology. This brief review will summarize the contributions of specific sPLA₂ isoforms as markers and mediators in ALI, supporting a potential therapeutic role for targeting them in ARDS.

Therapeutic effect of irbesartan combined with atorvastatin calcium in the treatment of rats with coronary heart disease

This study aimed to investigate the therapeutic effect of irbesartan combined with atorvastatin calcium in the treatment of rats with coronary heart disease. One hundred sixty Wistar rats were selected to establish coronary heart disease model. Rats with coronary heart disease were randomly divided into 4 groups: Model, irbesartan, atorvastatin calcium and combination groups (irbesartan combined with atorvastatin calcium group). Rats in irbesartan group were treated with 50 mg/(kg.day) irbesartan; rats in atorvastatin calcium group were given atorvastatin calcium at a dose of 10 mg/(kg.day); rats in combination group were subjected to atorvastatin calcium at a dose of 10 mg/(kg.day) and irbesartan at a dose of 50 mg/(kg.day), while rats in model groups were given intragastric administration of normal saline at a dose of 2 ml/day. Serum lipids, including total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and TC/HDL-C, were measured by automatic biochemical analyzer. Expression of sPLA2-V in myocardium and aortic trunk of rats was detected by reverse transcription-PCR (RT-PCR) and western blot analysis. After treatment, levels of serum TC, TG, LDL-C, HDL-C and TC/HDL-C in rats of each treatment group were better than those in model group (p<0.05). Expression level of sPLA2-V in myocardium and aortic trunk in model group was significantly higher than that in other groups (p<0.05). Expression level of sPLA2-V in combination group was significantly lower than that in irbesartan and atorvastatin calcium groups (p<0.05). Combination of irbesartan and atorvastatin calcium is superior to irbesartan or atorvastatin calcium alone in the treatment of rats with coronary heart disease. The possible explanation is that the two drugs can reduce the expression of sPLA2-V in myocardium and aortic trunk, which in turn relieved atherosclerosis and achieved better therapeutic effect.