Vascular ATGL-dependent lipolysis and the activation of cPLA2-PGI2 pathway protect against postprandial endothelial dysfunction.

Adipose triglyceride lipase (ATGL) is involved in lipolysis and displays a detrimental pathophysiological role in cardio-metabolic diseases. However, the organo-protective effects of ATGL-induced lipolysis were also suggested. The aim of this work was to characterize the function of lipid droplets (LDs) and ATGL-induced lipolysis in the regulation of endothelial function. ATGL-dependent LDs hydrolysis and cytosolic phospholipase A2 (cPLA2)-derived eicosanoids production were studied in the aorta, endothelial and smooth muscle cells exposed to exogenous oleic acid (OA) or arachidonic acid (AA). Functional effects of ATGL-dependent lipolysis and subsequent activation of cPLA2/PGI2 pathway were also studied in vivo in relation to postprandial endothelial dysfunction.The formation of LDs was invariably associated with elevated production of endogenous AA-derived prostacyclin (PGI2). In the presence of the inhibitor of ATGL or the inhibitor of cytosolic phospholipase A2, the production of eicosanoids was reduced, with a concomitant increase in the number of LDs. OA administration impaired endothelial barrier integrity in vitro that was further impaired if OA was given together with ATGL inhibitor. Importantly, in vivo, olive oil induced postprandial endothelial dysfunction that was significantly deteriorated by ATGL inhibition, cPLA2 inhibition or by prostacyclin (IP) receptor blockade.In summary, vascular LDs formation induced by exogenous AA or OA was associated with ATGL- and cPLA2-dependent PGI2 production from endogenous AA. The inhibition of ATGL resulted in an impairment of endothelial barrier function in vitro. The inhibition of ATGL-cPLA2-PGI2 dependent pathway resulted in the deterioration of endothelial function upon exposure to olive oil in vivo. In conclusion, vascular ATGL-cPLA2-PGI2 dependent pathway activated by lipid overload and linked to LDs formation in endothelium and smooth muscle cells has a vasoprotective role by counterbalancing detrimental effects of lipid overload on endothelial function.

Eicosanoid profiling in effluent of isolated perfused heart of Tgαq*44 mice with advanced heart failure.

A plethora of studies have suggested the involvement of various eicosanoids in heart failure. The aim of this study was to profile eicosanoid release from isolated murine heart at transition and end-stage phases of heart failure (HF) in Tgαq*44 mice as compared with age-matched wild-type FVB mice. Using an UPLC-MS/MS-based method, the concentration of selected eicosanoids was measured in cardiac effluents collected from isolated perfused mice hearts according to the Langendorff technique in Tgαq*44 and FVB mice (8- and 12-month-old) in basal conditions and in response to bolus injection of arachidonic acid (AA), a major substrate for eicosanoids. In basal conditions, only some eicosanoids were detected in the coronary effluents, with 6-keto-PGF1α, PGD2, 12-HETE detected at the highest concentration. In response to AA, a wide range of its metabolites was detected, including not only prostanoids and HETEs, but also EETs and DHETs. Cardiac production of 6-keto-PGF1α, PGD2, PGE2, PGF2α, TXB2 in basal conditions was unchanged at the transition phase of HF, whereas it was increased at the end-stage of disease in Tgαq*44 mice as compared with age-matched FVB mice. In response to AA, the synthesis of PGE2, 12-, 15-HETEs, 8,9-, 11,12-DHETs were also elevated at the end-stage phase of HF in Tgαq*44 mice as compared to healthy animals. AA-induced vasodilation effect was greater at the end-stage phase of HF in Tgαq*44 mice as compared with age-matched FVB mice, but it was not changed at the transition phase of the disease. In conclusion, eicosanoid profiling in isolated perfused heart pointed to PGI2, PGD2 and 12-HETE as the most abundant AA metabolites of the isolated murine heart. In Tgαq*44 mice, the end-stage phase of heart failure was accompanied by major activation of cyclooxygenase pathways (PGI2, TXA2, PGD2, PGE2, PGF2α), 8,9-, 11,12-EET/DHETs pathways and 12-, 15-HETEs pathways in the heart.

Differential effects of nitric oxide deficiency on primary tumour growth, pulmonary metastasis and prostacyclin/thromboxane A2 balance in orthotopic and intravenous murine models of 4T1 breast cancer.

The role of nitric oxide (NO) in tumour progression and metastasis is not clear, therefore the present work aimed to better characterise the effects of nitric oxide synthase (NOS) inhibition by L-Nω-nitroarginine methyl ester (L-NAME) on primary tumour growth, pulmonary metastasis, inflammatory state and prostacyclin (PGI2)/thromboxane A2 (TXA2) balance in a 4T1 murine model of breast cancer. To distinguish effects of NO deficiency on disease development, 4T1 cancer cells were administered orthotopically or intravenously to Balb/c mice. The systemic NO bioavailability, pulmonary inflammation and plasma levels of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1α (6-keto-PGF1α) were assessed. The study shows that, in the orthotopic model of 4T1 breast cancer, L-NAME hampered primary tumour growth, reduced pulmonary metastases, delayed inflammatory response but did not alter biosynthesis of TXB2 and 6-keto-PGF1α as well as PGI2/TXA2 ratio in cancer-bearing mice. Interestingly, in the intravenous model of 4T1 breast cancer, NOS inhibition did not influence metastasis nor inflammation, but it increased both TXB2 and 6-keto-PGF1α biosynthesis without affecting PGI2/TXA2 ratio. In conclusion, in a 4T1 murine model of metastatic breast cancer, NO plays a major role in primary tumour development, while NO is not the key mediator of cancer cell extravasation to the lungs. Furthermore, NO-deficiency activates a PGI2-dependent compensatory mechanism only in the intravenous model of 4T1 breast cancer.