Influence of omega-3 fatty acids on bovine luteal cell plasma membrane dynamics

N-3 Polyunsaturated Fatty Acids as a Nutritional Support of the Reproductive and Immune System of Cattle-A Review

This paper focuses on the role of n-3 fatty acids as a nutrient crucial to the proper functioning of reproductive and immune systems in cattle. Emphasis was placed on the connection between maternal and offspring immunity. The summarized results confirm the importance and beneficial effect of n-3 family fatty acids on ruminant organisms. Meanwhile, dietary n-3 fatty acids supplementation, especially during the critical first week for dairy cows experiencing their peripartum period, in general, is expected to enhance reproductive performance, and the impact of its supplementation appears to be dependent on body condition scores of cows during the drying period, the severity of the negative energy balance, and the amount of fat in the basic feed ration. An unbalanced, insufficient, or excessive fatty acid supplementation of cows' diets in the early stages of pregnancy (during fetus development) may affect both the metabolic and nutritional programming of the offspring. The presence of the polyunsaturated fatty acids of the n-3 family in the calves' ration affects not only the performance of calves but also the immune response, antioxidant status, and overall metabolism of the future adult cow.

Trafficking of cholesterol from lipid droplets to mitochondria in bovine luteal cells: Acute control of progesterone synthesis

The corpus luteum is a transient endocrine gland that synthesizes and secretes the steroid hormone, progesterone, which is vital for establishment and maintenance of pregnancy. Luteinizing hormone (LH) via activation of protein kinase A (PKA) acutely stimulates luteal progesterone synthesis via a complex process, converting cholesterol via a series of enzymatic reactions, into progesterone. Lipid droplets in steroidogenic luteal cells store cholesterol in the form of cholesterol esters, which are postulated to provide substrate for steroidogenesis. Early enzymatic studies showed that hormone sensitive lipase (HSL) hydrolyzes luteal cholesterol esters. In this study, we tested whether HSL is a critical mediator of the acute actions of LH on luteal progesterone production. Using LH-responsive bovine small luteal cells our results reveal that LH, forskolin, and 8-Br cAMP-induced PKA-dependent phosphorylation of HSL at Ser563 and Ser660, events known to promote HSL activity. Small molecule inhibition of HSL activity and siRNA-mediated knock down of HSL abrogated LH-induced progesterone production. Moreover, western blotting and confocal microscopy revealed that LH stimulates phosphorylation and translocation of HSL to lipid droplets. Furthermore, LH increased trafficking of cholesterol from the lipid droplets to the mitochondria, which was dependent on both PKA and HSL activation. Taken together, these findings identify a PKA/HSL signaling pathway in luteal cells in response to LH and demonstrate the dynamic relationship between PKA, HSL, and lipid droplets in luteal progesterone synthesis.

Inflammation and angiogenesis in the corpus luteum

Angiogenesis is a very important process that helps establish and maintain the normal structure and function of the corpus luteum (CL). Early luteal development can be considered a kind of physiological injury with an inflammatory response; therefore, the inflammatory response may play an important role in the luteal angiogenesis. The inflammatory response is companied by activated leukocytes and their mediators. For luteal tissue, numerous activated leukocytes such as macrophages, neutrophils and eosinophils are present in the early luteal phase and are widely involved in neovascularization. The objective of this review is to describe the role of the inflammatory factors in the angiogenesis and to discuss their mechanism. Knowledge of action and mechanism of these inflammatory factors on angiogenic activity will be beneficial for the understanding of luteal function.

Docosahexaenoic acid and TUG-891 activate free fatty acid-4 receptor in bovine neutrophils

Fatty acids are well known metabolic intermediaries but also have a role in the immune response. Long-chain fatty acids such as omega-6 and -9 activate neutrophil function through free fatty acid (FFA)-1 receptor in bovines. Although omega-3 has also been suggested to influence neutrophil function, the details remain unclear. The goal of this study was to determine the presence of the bovine FFA4 receptor and its effect on neutrophil responses. We treated bovine neutrophils with the natural and synthetic agonists of FFA4 receptor docosahexaenoic acid (DHA) and TUG-891, respectively, and assessed oxidative and no oxidative response. We detected protein and mRNA FFA4 receptor expression through immunofluorescence, immunoblot, and RT-PCR analysis. DHA and TUG-891 both increased intracellular calcium mobilisation in bovine neutrophils, with 50% effective concentrations of 99 μM and 73 μM, respectively, which was partially reduced after treatment with the FFA4 antagonist AH7614. Furthermore, DHA and TUG-891 increased matrix metalloproteinase (MMP)-9 granules release and superoxide production. AH7614 and the intracellular calcium chelator BAPTA-AM decreased the superoxide production induced by TUG-891 and by both DHA and TUG-891, respectively, suggesting a key role of intracellular calcium in FFA4 agonists-induced superoxide production. These results highlight an important mechanism of bovine neutrophil responses mediated via FFA4 receptor, which can further inform the development of new formulations for DHA-enriched feed supplements to enhance innate immunity in dairy cattle.

Soluble transforming growth factor beta-1 enhances murine mast cell release of Interleukin 6 in IgE-independent and Interleukin 13 in IgE-dependent settings in vitro

INTRODUCTION

For immune cells transforming growth factor beta-1 (TGF-β1) can enhance or repress effector functions. Here, we characterize the effects of TGF-β1 on IgE-mediated and IL-33-mediated activation of primary murine mast cells derived from hematopoietic stem cells (bone marrow derived mast cells; BMMC). We also investigated potential interactions between TGF-β1 and stem cell factor (SCF). We conclude TGF-β1 plays a selectively stimulatory role for mast cell cultures in vitro.

METHODS

BMMCs from C57BL/6 mice were differentiated with IL-3 and then treated with TGF-β1. BMMCs were exposed to TGF-β1, primed with IgE, activated with antigen, and then IL-6 and IL-13 cytokine release was quantified using ELISA. Additionally, the effects of TGF-β1 on both IgE and IL-33-mediated short term activation were observed via flow cytometric analysis of both surface LAMP-1 expression and intracellular IL-6. Receptor colocalization was visualized using fluorescence confocal microscopy and individual receptor expression levels were also quantified.

RESULTS

Resting IL-6 production increased with TGF-β1 but significance was lost following BMMC activation via IgE receptor (FcεRI) crosslinking. This was similar to a comparison effect due to SCF treatment alone, which also enhanced resting levels of IL-6. TGF-β1 treatment enhanced release of IL-13 only with FcεRI-IgE-mediated activation. TGF-β1 suppressed mobilization of IL-6 with short-term BMMC activation when stimulated with IL-33. Lastly, colocalization patterns of the SCF receptor (CD117) and FcεRI with IgE crosslinking were unaffected by TGF-β1 treatment, but individual expression levels for FcεRI, CD117, and TGFβRII were all reduced following either IgE activation or TGF-β1 treatment; this reduction was partially recovered in BMMCs that were both activated by IgE and treated with TGF-β1.

DISCUSSION

These data reveal a novel positive effect of soluble TGF-β1 on mast cell activation in vitro, suggesting mast cells may be activated through a non-canonical pathway by TGF-β1. Understanding this interaction will provide insight into the potential role of mast cells in settings where TGF-β1 is produced in an aberrant manner, such as in and around high grade tumors.

Effect of fish oil on agonist-induced receptor internalization of the PG F2α receptor and cell signaling in bovine luteal cells in vitro

Many receptors span the plasma membrane allowing for signal transduction, converting extracellular signals into intracellular signals. Following ligand-induced activation, membrane-bound receptors are taken into endocytic vesicles, where they are targeted for degradation or recycled back to the plasma membrane. The objectives of the present study were to determine the influence of fish oil on (1) PGF_2α-induced receptor internalization and trafficking of the PGF_2α (FP) receptor, (2) cytoskeletal structural integrity, and (3) PGF_2α-induced mitogen-activated protein kinase (MAPK) signaling in bovine luteal cells. Bovine ovaries were obtained from a local abattoir and corpora lutea (CL; n = 4-6) were digested using collagenase. For all experiments, cells were incubated in either BSA or fish oil-supplemented media for 72 h to allow incorporation of omega-3 fatty acids into biological membranes. Confocal microscopy was used to determine the influence of fish oil on PGF_2α-induced receptor internalization and trafficking of the FP receptor and cytoskeletal structural integrity. In addition, Western blotting was used to determine the effects of fish oil on PGF_2α-induced MAPK signaling in bovine luteal cells. Results from the present study demonstrate that fish oil disrupts the colocalization of G_αq with both caveola microdomains and FP receptor as well as PGF_2α-induced MAPK signaling. This disruption of the FP receptor with the G-protein alpha subunit may be one mechanism by which a MAPK signaling is diminished following the addition of PGF_2α. Furthermore, fish oil disrupts FP receptor internalization and endosomal protein trafficking without detectable changes in the cytoskeleton.