Effect of boar semen supplementation with recombinant heat shock proteins during summer.

Artificial insemination (AI) in pigs is mainly performed with refrigerated boar semen. There is a marked negative seasonal effect on the quality of boar sperm, mainly due to relatively greater ambient temperatures; to counteract this thermal stress, sperm cells possess natural defensive mechanisms such as Heat Shock Proteins (HSPs) that prevent protein denaturation. Thus, the objective of this research was to improve the quality of commercial boar semen collected during the summer when ambient temperatures are greater using recombinant HSPs. For this purpose, different concentrations (0.1, 0.5 and 1 µg/ml) of recombinant heat shock proteins (HSPD1, HSPA8 or HSP86) were added to commercial boar semen and there was cooling for 48 h at 17 °C. After this storage period, sperm quality was assessed by analyzing sperm viability, mitochondrial membrane potential and plasma membrane lipid organization using flow cytometry; additionally, sperm motility was examined using a CASA system. Also, in vitro fertilization (IVF) using HSP-supplemented boar semen was performed and the quality of the embryos produced was evaluated using quantitative real-time polymerase chain reaction (qPCR) analyzing the relative abundance of mRNA transcripts for genes encoding for embryo quality-related proteins (BAX, TFAM, POLG and POG2). Sperm quality variables, blastocyst rates and the abundance of mRNA transcripts for the selected genes were not affected by the presence of recombinant HSPs at any concentration. These results indicate that the supplementation of commercial seminal doses with recombinant HSPs does not improve boar sperm quality or fertility during the summer months when ambient temperatures are greater.

Arginase I induction by modified lipoproteins in macrophages: a peroxisome proliferator-activated receptor-gamma/delta-mediated effect that links lipid metabolism and immunity.

Macrophages are phagocytic cells that play essential roles in innate immunity and lipid homeostasis. The uptake of modified lipoproteins is an important early event in the development of atherosclerosis. We analyzed the ability of modified low-density lipoprotein (LDL) (oxidized and acetylated) to alter the expression and activity of arginases (ArgI and ArgII) in macrophages. We show that ArgI expression is potently induced by both oxidized and acetylated LDL in macrophages. We further show that this effect is mediated by peroxisome proliferator-activated receptors (PPAR). ArgI expression is highly responsive to agonists for PPARgamma and PPARdelta but not PPARalpha. Moreover, the induction of ArgI by both PPAR agonists and IL-4 is blocked in macrophages from PPARgamma- and PPARdelta-deficient mice. Functionally, PPAR activity induces macrophage activation toward a more Th2 immune phenotype in a model of Leishmania major infection. We show that PPARgamma and -delta ligands promote intracellular amastigote growth in infected macrophages, and this effect is dependent on both PPAR expression and Arg activity. Collectively, our results strongly suggest that ArgI is a key marker of the alternative program triggered by PPAR in macrophages.