No abstract

Monocyte chemoattractant protein-1 (MCP-1) is a potential mediator of the recruitment of monocytes/macrophages into the regressing corpus luteum (CL). We investigated whether the luteolytic effect of prolactin in the rat is associated with the expression of MCP-1 and an invasion of monocytes/macrophages. Ovulation was induced in immature female rats by injection of eCG (5 IU, s.c.) at 30 days of age. All rats were hypophysectomized 3 days later. Rats received injections of ovine prolactin (250 micrograms, s.c.) at 12-h intervals on Day 9, 10, and 11 posthypophysectomy; controls received injection of vehicle. Rats were killed by decapitation 24, 48, or 72 h after the first injection of prolactin or vehicle. In rats treated with prolactin, immunoreactive MCP-1 was detected in the CL at 24 h after the first injection, and a consistent level of staining was reached by 72 h with immunodetectable MCP-1 diffused throughout individual CL. The number of monocytes/macrophages in the CL (mean +/- SEM) increased significantly after prolactin treatment, from 3.1 +/- 1.8 at 24 h to 49.3 +/- 8.2 at 72 h (p < 0.05), and the number of monocytes/macrophages was different from that in control, vehicle-treated rats at 72 h (10.3 +/- 4.1; p < 24 and 72 h in prolactin-treated rats (p < 0.05). It is concluded that a potentially important component of the luteolytic effect of prolactin in the rat is the expression of MCP-1 and invasion of monocytes/macrophages into the CL.

The purpose of this study was to determine the effect of cryotherapy on the inflammatory response to muscle-damaging exercise using a randomized trial. Twenty recreationally active males completed a 40-min run at a -10 % grade to induce muscle damage. Ten of the subjects were immersed in a 5 °C ice bath for 20 min and the other ten served as controls. Knee extensor peak torque, soreness rating, and thigh circumference were obtained pre- and post-run, and 1, 6, 24, 48, and 72 h post-run. Blood samples were obtained pre- and post-run, and 1, 6 and 24 h post-run for assay of plasma chemokine ligand 2 (CCL2). Peak torque decreased from 270 ± 57 Nm at baseline to 253 ± 65 Nm post-run and increased to 295 ± 68 Nm by 72 h post-run with no differences between groups (p = 0.491). Soreness rating increased from 3.6 ± 6.0 mm out of 100 mm at baseline to 47.4 ± 28.2 mm post-run and remained elevated at all time points with no differences between groups (p = 0.696). CCL2 concentrations increased from 116 ± 31 pg mL(-1) at baseline to 293 ± 109 pg mL(-1) at 6 h post-run (control) and from 100 ± 27 pg mL(-1) at baseline to 208 ± 71 pg mL(-1) at 6 h post-run (cryotherapy). The difference between groups was not significant (p = 0.116), but there was a trend for lower CCL2 in the cryotherapy group at 6 h (p = 0.102), though this measure was highly variable. In conclusion, 20 min of cryotherapy was ineffective in attenuating the strength decrement and soreness seen after muscle-damaging exercise, but may have mitigated the rise in plasma CCL2 concentration. These results do not support the use of cryotherapy during recovery.

This study characterizes the expression of monocyte chemoattractant protein-1 (MCP-1) and the relative distribution of immune cell populations in the bovine corpus luteum throughout the estrous cycle. Immunodetectable MCP-1 was evident in corpora lutea of cows at Days 6, 12, and 18 postovulation (Day 0 = ovulation, n = 4 cows/stage). Day 6 corpora lutea contained minimal MCP-1 that was confined primarily to blood vessels. In contrast, relatively intense staining for MCP-1 was observed in corpora lutea from Days 12 and 18 postovulation. MCP-1 was again most evident in the cells of the vasculature, but it was also observed surrounding individual luteal cells, particularly by Day 18. An increase in immunohistochemical expression of MCP-1 on Days 12 and 18 postovulation corresponded with increases in MCP-1 mRNA and protein in corpora lutea as determined by Northern blot analysis and ELISA. Monocytes and macrophages were the most abundant immune cells detected in the bovine corpus luteum, followed by CD8+ and CD4+ T lymphocytes. In all instances, Day 6 corpora lutea contained fewer immune cells than corpora lutea from Days 12 and 18. In conclusion, increased expression of MCP-1 was accompanied by the accumulation of immune cells in the corpora lutea of cows during the latter half of the estrous cycle (Days 12-18 postovulation). These results support the hypothesis that MCP-1 promotes immune cell recruitment into the corpus luteum to facilitate luteal regression. These results also raise a provocative issue, however, concerning the recruitment of immune cells several days in advance of the onset of luteal regression.

Information regarding the regulation of monocyte chemoattractant protein-1 (MCP-1) in regression of the corpus luteum (CL) is limited. This study tested the hypothesis that endothelial cells derived from bovine CL are a source of MCP-1, and that proinflammatory cytokines, prostaglandin F2alpha (PGF2alpha), and progesterone regulate MCP-1 expression. Endothelial cells were treated without (Control) or with PGF2alpha (1 micro M), TNFalpha (100 ng/ml), interferon-gamma (IFNgamma, 200 IU/ml), and TNFalpha + IFNgamma for 24 and 48 h in the absence or presence of progesterone (P4, 250 ng/ml). Increases in MCP-1 mRNA and protein were observed in response to TNFalpha within 24 and 48 h of culture, respectively (P < 0.05). Interferon-gamma stimulated (P < 0.05) both MCP-1 mRNA and protein after 24 h of culture, and this effect was also sustained through 48 h of culture (P < 0.05). Cotreatment of cultures with TNFalpha + IFNgamma lead to further increases (P < 0.05) in MCP-1 in both 24- and 48-h cultures. Surprisingly, neither PGF2alpha nor P4 affected MCP-1 production. Subsequent experiments revealed that the endothelial cells lacked prostaglandin F2alpha receptor mRNA, and the MAPK pathway, although present and responsive to growth factor stimulation, was unresponsive to PGF2alpha stimulation. In summary, endothelial cells derived from bovine CL respond to TNFalpha and IFNgamma stimulation with an increase in MCP-1 secretion. In contrast, neither PGF2alpha nor P4 directly influenced endothelial expression of MCP-1. These results suggest that cytokines stimulate the synthesis of MCP-1 observed during PGF2alpha-induced luteal regression.

The known accumulation of macrophages in corpora lutea (CL) at the time of luteal regression prompted us to investigate whether the chemoattractant protein monocyte chemoattractant protein-1 (MCP-1) is expressed in the rat CL. On the day of confirmed mating (Day 0 of pregnancy), regressing CL from the previous (nonfertile) estrous cycle contained immunodetectable MCP-1 and numerous monocytes/macrophages, whereas the newly formed CL of pregnancy, within the same ovary, contained little MCP-1 and few monocytes/macrophages. MCP-1 diminished in the regressing CL on Days 3 and 9 of pregnancy, although numerous monocytes/macrophages remained. The CL of pregnancy on Days 3 and 9 of pregnancy contained minimal MCP-1 and relatively few monocytes/macrophages. By Days 17 and 21 of pregnancy, however, prior to parturition and prior to an accumulation of monocytes/macrophages, expression of MCP-1 increased in the CL of pregnancy. Northern blots revealed a resurgence of luteal MCP-1 mRNA on Day 21 of pregnancy: 3805 +/- 1077 on Day 21 vs. 1059 +/- 177 on Day 9 (p < 0.05; expressed as densitometric units relative to beta-actin). In conclusion, the expression of MCP-1 in the rat CL in association with, or preceding, the appearance of monocytes/macrophages at the time of luteal regression is consistent with the known role of MCP-1 as a potent chemoattractant for monocytes/macrophages. This suggests that MCP-1 might have a prominent role in the immunological process of luteal regression.

The recent characterization of the mitochondrial protein, Steroidogenic Acute Regulatory (StAR) protein, as a rate-limiting protein in steroidogenesis prompted us to investigate whether StAR is expressed in the rabbit corpus luteum and whether the expression of StAR is responsive to estradiol-17 beta, the luteotropic hormone in the rabbit. In rabbits treated continuously with exogenous estradiol through Day 13 of pseudopregnancy (n = 9), immunoblot analysis revealed that luteal expression of StAR was stable, ranging from 8.5 to 9.7 U of corrected integrated optical density. Plasma progesterone concentration (mean +/- SEM) remained elevated in these rabbits (14.3 +/- 2.1 ng/ml). In contrast, expression of StAR decreased in corpora lutea of rabbits deprived of estradiol for the last 48 and 72 h of the experiment (4.9 +/- 2.2 and 0.3 +/- 0.2 U, respectively, n = 3 per group), and was associated with a decline in plasma progesterone (0.8 +/- 0.1 and 0.5 +/- 0.3 ng/ml, respectively). Replacement of estradiol after 48 h of estradiol deprivation (n = 3) stimulated the reappearance of StAR (10.3 +/- 2.6 U) and the restoration of plasma progesterone (10.4 +/- 4.9 ng/ml). [35S]Methionine labeling of proteins in rabbit corpora lutea revealed that several isoforms of StAR protein were specifically synthesized in response to estradiol treatment. Collectively, these observations are consistent with a proposed role for StAR in the mediation of the luteotropic effect of estrogen to promote the synthesis of progesterone in the rabbit.

Prostaglandins produced within the CL may serve as local modulators of CL function. The present study was designed to characterize the cellular mechanisms by which the cytokine interleukin-1 beta (IL-1 beta) stimulates prostaglandin production in cultured luteal cells. Cycloheximide (CHX) and actinomycin D (Act D) did not affect basal, but completely inhibited IL-1 beta-stimulated prostaglandin F2 alpha (PGF2 alpha) production (p < 0.05). The phospholipase A2 (PLA2) inhibitor, aristolochic acid (PLA2X), and the phospholipase C (PLC) inhibitor, compound 48/80 (PLCX), suppressed IL-1 beta-stimulated (p < 0.05), but not basal, PGF2 alpha production. The addition of exogenous arachidonic acid (AA) restored the stimulatory effect of IL-1 beta in PLCX-treated, but not in PLA2X-treated, cells, suggesting that PLA2 is a key regulatory point of IL-1 beta action. Chronic exposure of the luteal cells to IL-1 beta resulted in stimulatory effects beyond that of increasing AA availability, presumably by up-regulation of prostaglandin endoperoxide (PGH) synthase. Chronic exposure of luteal cells to IL-1 beta also inhibited progesterone production, but this effect appeared to be independent of endogenous PGF2 alpha production. The ability of IL-1 beta to comprehensively stimulate luteal PGF2 alpha production while inhibiting luteal progesterone production is suggestive that IL-1 beta may facilitate regression of the CL.