Changes in plasma hormone levels following lipopolysaccharide injection in rabbits

The half-lives of intact and elastase cleaved human corticosteroid-binding globulin (CBG) are identical in the rabbit

Corticosteroid-binding globulin (CBG) is a non-inhibitory member of the serpin superfamily of serine protease inhibitors and carries the majority of cortisol in circulation. It can be cleaved by neutrophil elastase at its exposed reactive centre loop which decreases its affinity for cortisol allowing the release of most of the cortisol at sites of inflammation. Intact and elastase cleaved CBG can be distinguished from each other and can coexist in circulation but with unknown half-lives. Here we treated a portion of purified human CBG with elastase, terminated the digestion and then combined this portion with intact human CBG and measured their respective half-lives in rabbits by ELISA. This investigation shows for the first time that the half-lives of intact and elastase cleaved CBG are identical (∼10h). This is an important finding as it implies that in conditions such as sepsis and septic shock where levels of intact CBG are low and the proportion of cleaved CBG is high that this is likely sustained which may affect the CBG mediated targeted delivery of cortisol to sites of inflammation. Furthermore the residual binding of cortisol to cleaved CBG may alter the overall buffering capacity of CBG for cortisol resetting the baseline concentration of free cortisol.

Comparison of immune response to lipopolysaccharide of rabbit does selected for litter size at weaning or founded for reproductive longevity

To evaluate differences in maternal lines to the immune response of reproductive rabbit does, a total of 64 animals of two different lines: (1) founded for hyper-longevity and litter size criteria (LP) and (2) selected for litter size at weaning (V) were used. Females were subjected to three different reproductive efforts: post-partum (PP) mating at first lactation and 9 kits during the second; post-weaning (PW) mating at first lactation and 9 kits during the second; and PW mating at first lactation and 5 kits during the second. At second weaning (30 days PP), an acute response was induced by intravenous infusion of lipopolysaccharide (LPS). LP females seemed to be lower affected during the hyper-acute phase than V females, showing lower plasma glucose content at 1.5 h post infusion (pi) and rectal temperature at 6 h pi; and showed higher ulterior immune response, with higher levels of C-reactive protein at 48 h pi and haptoglobin in plasma from 24 h pi. Survival test conferred a higher risk of culling for V than for LP females during the first hours after challenge. These results may suggest that, regarding immune response to LPS challenge, foundation by hyper-longevity productive criteria lead to obtain a more robust population of rabbit does, characterized by improved response ability.

Anti-inflammatory and analgesic effects displayed by peptides derived from PKI55 protein, an endogenous protein kinase C inhibitor

We recently characterized the PKI55 protein as an endogenous protein kinase C (PKC) inhibitor and investigated, in vitro, the potential anti-inflammatory actions of its N-terminal peptides 1-16 (peptide 5), 1-8 (peptide 8) and 1-5 (peptide 9). We showed their ability to inhibit chemotaxis in human polymorphonuclear leukocytes activated by the N-formyl tripeptide for-Met-Leu-Phe-OMe. In this work, we evaluated the anti-inflammatory and the analgesic effects of the selected peptides by in vivo experiments carried out in the mouse. The peptides 5, 8 and 9 (0.1 and 10 nmol i.c.v.) were effective in both the parameters chosen to test the anti-inflammatory activity, i.e., the xylene-induced ear edema and the acetic acid-induced infiltration of neutrophils in the peritoneal cavity. In addition, they displayed analgesic effect, evaluated by the acetic acid-induced writhing test. All the peptides' effects were shared by the reference compounds, dexamethasone and indomethacin (10 mg kg(-1) i.p.), but not by the 9-scramble peptide (10 nmol i.c.v.). The peptide 9, which represents the shortest active sequence of the PKI55 protein, was tested in the ear edema model even following intraperitoneal (i.p.) administration and proved to be effective in the range doses 3-30 mg kg(-1). Moreover, an increase in plasma corticosterone levels was detected in mice treated with the peptide 9, but not with the 9-scramble peptide (both at 10 nmol i.c.v.). The anti-inflammatory and analgesic effects of the PKI55-derived synthetic peptides, possibly related both to PKC inhibition and hypothalamic-pituitary-adrenal axis activation, deserve further investigation in view of potential therapeutic exploitation.

Short- and long-term effects of lipopolysaccharide-induced inflammation on rabbit sperm quality

Infections and resulting inflammation are widely known to cause transient or permanent male infertility. The objectives of this study were (1) to provide a suitable animal model of a sub-acute inflammatory state by intraperitoneally inoculating bacterial lipopolysaccharides (LPS) and (2) to define the short- and long-term effects of this state on the sperm quality of rabbit bucks. Two series of experiments were performed to accomplish these objectives. In experiment 1, 15 healthy New Zealand White rabbit bucks were divided into five homogeneous groups, receiving 25, 50, 100 and 150 microg/kg body weight (b.w.) of E. coli LPS dissolved in 2ml of sterile saline or only saline (control), respectively. White blood cells (WBC), rectal temperature, feed intake and mating ability were observed for 3 consecutive days following inoculation. Inoculation of 50 microg/kg b.w. produces a reversible inflammation-like state that lasts for about 3 days, with minimal distress to the animals, and therefore it was used in our experiment. The major symptoms were fever and anorexia. Changes in WBC count and a moderate reduction in reproductive activity also occurred. In experiment 2, two groups of five rabbit bucks each were treated with 50 microg/kg b.w. E. coli LPS diluted in 2ml of saline or only saline (controls), respectively. Semen samples were collected weekly up to 56 days after inoculation and the changes in semen characteristics were examined. During the first 3 days, semen volume and concentration decreased in both experimental groups, probably due to the high collection frequency. Sperm membrane integrity and the number of necrotic sperm were seriously affected 30 days after the LPS challenge, reaching a maximum at the end of the spermatogenic cycle (56 days). These results suggest that a sub-acute inflammation may cause infertility by compromising sperm membrane integrity which decreases a month after LPS-treatment. In addition, the rabbit could be a useful LPS animal model for further study of the effects of inflammation and the underlying mechanisms on sperm characteristics.