Mediators of inflammation

Effect of cryotherapy duration on experimentally induced connective tissue inflammation in vivo

Objectives

This study tested the hypothesis that cryotherapy duration influences lipopolysaccharide (LPS)-induced inflammation in a rat model.

Materials and Methods

Six Wistar rats (Rattus norvegicus albinus) were used. Five sites were selected per animal and divided into 5 groups: a negative control group (NC), 2 positive control groups (PC1 and PC2), and 2 experimental groups (E1 and E2). Cryotherapy was applied for 1 minute (E1) or 5 minutes (E2). An acute inflammatory response was induced in the PC and E groups via subcutaneous administration of 0.5 mL/kg. In the PC2 group, a catheter was inserted without additional treatment. For the E1 and E2 groups, 2.5°C saline solution was administered through the implanted catheters for 1 and 5 minutes, respectively. The rats were sacrificed, and samples were obtained and processed for histological analysis, specifically examining the presence of polymorphonuclear neutrophils and hemorrhage. The χ2 test was used to compare the presence of acute inflammation across groups. Dependent variables were compared using the linear-by-linear association test.

Results

Inflammation and hemorrhage varied significantly among the groups (p = 0.001). A significantly higher degree of acute inflammation was detected (p = 0.0002) in the PC and E1 samples than in the E2 group, in which cryotherapy was administered for 5 minutes. The PC and E1 groups also exhibited significantly greater numbers of neutrophils (p = 0.007), which were essentially absent in both the NC and E2 groups.

Conclusions

Cryotherapy administration for 5 minutes reduced the acute inflammation associated with LPS and catheter implantation.

A low molecular weight proinflammatory factor from rat spleen lymphocytes. Isolation and partial characterization

A dialyzable low molecular weight proinflammatory factor (X (2)) from rat spleen lymphocytes was isolated through a combination of gel filtration and high voltage paper electrophoresis (HVE) and then partially characterized. It was able to potentiate the formation of carrageenin induced edema on the rat paw. Its amino acid analysis revealed Glu, Cys and Gly (1:1:1), but gammaGlu as N-terminal residue, initially suggesting oxidized glutathione (GSSG), since it showed exactly the same HV electrophoretic mobility as GSSG at pH 6.5. However, neither GSSG nor a synthetic homologue showed any proinflammatory activity. On basis of its infrared spectrum, HVE mobility and presence of a gamma-Glu-Cys-Gly (GSH) moiety, the hypothesis of identity of X (2) with leukotriene C(4) (LTC(4)) was raised. Once again it was not confirmed, since LTC(4) did not show any proinflammatory activity too, leading us to infer that, even excluding LTC(4), our data are consistent with a structure bearing a GSH moiety conjugated with a hydroxylated insaturated fatty acid chain which contributes a -COO(-) group, thus providing a final net charge of -2 at pH 6.5 and an Mr = 600-650.

A factor in serum lowers resistance and opens tight junctions of MDCK cells

During an inflammatory reaction, factors in blood affect the permeability of endothelium and possibly organ epithelium. In this study we partially characterized a factor in human and canine blood that lowered the transepithelial electrical resistance (TER) of canine kidney epithelial cells (MDCK) and examined whether vascular permeability factors [complement component C3a and C5a and platelet-activating factor (PAF)] were responsible for this reaction. C3a and C5a caused a small (10-13%) dose-related decrease in the TER (alpha = 0.05), whereas PAF had no effect. In contrast, the factor found in both serum and plasma caused a large (60-83%) dose-dependent decrease (saturated at 30%) in the TER that was reversible within 60 min. The blood factor, which does not appear to be albumin, was heat stable and has an apparent molecular mass of 67 kDa. It preferentially decreased the TER of the epithelium when it came in contact with its basolateral surface and significantly lowered the resistance within 60 min by opening the zonula occludentes. These findings suggest that C3a, C5a, and a factor in blood can directly modulate the permeability of renal epithelium.