The effect of dexamethasone in vivo on blood and peritoneal neutrophils (PMN) in rabbits with peritonitis

Concomitant coiling reduces metalloproteinase levels in flow diverter-treated aneurysms but anti-inflammatory treatment has no effect

Background and purpose

Flow diverters (FD) can cause rare but devastating delayed aneurysm ruptures in which matrix metalloproteinases (MMPs) have been potentially implicated. Concomitant coiling or anti-inflammatory medications have been proposed to prevent the risk of delayed ruptures. The aim of this study was to evaluate concomitant coiling and ciclosporin in regulating the expression of MMPs in FD-treated aneurysms.

Materials and methods

Elastase-induced aneurysms were created in 20 rabbits. Aneurysms were treated with (1) FD alone; (2) FD with concomitant coiling; (3) FD+ ciclosporin; or (4) left untreated as controls. At sacrifice, MMP levels were analyzed by zymography. Kruskal–Wallis one-way non-parametric ANOVA was performed for each enzyme. If significant results were observed for the Kruskal–Wallis test, pairwise group comparisons were performed using Dunn's test with Bonferroni multiple-testing correction.

Results

Significant differences were observed among groups for pro-MMP9 (p=0.0337). Pairwise comparison demonstrated higher levels of pro-MMP9 with concomitant coiling compared with untreated aneurysms (p=0.012), with higher though not significantly different levels of pro-MMP9 in FD with concomitant coiling versus FD alone. While not statistically significant, trends were noted regarding differences in active-MMP9 across groups, with a lower level of active-MMP9 with concomitant coiling compared with the other FD groups. No significant differences were observed for pro- or active-MMP2 across groups, or for FD + ciclosporin compared with FD alone.

Conclusions

FD implantation increases the level of pro-MMP9 expression in aneurysms. Provocative trends regarding modulation of active-MMP9 expression with concomitant coiling suggest the need for larger confirmatory preclinical studies. Anti-inflammatory treatment with ciclosporin appears to have a minimal biological effect.

Trial registration number

R01NS076491

Inhibitory capacity of different steroids on neutrophil migration across a bilayer of endothelial and bronchial epithelial cells

Neutrophil infiltration to the airway lumen is a common feature of respiratory inflammatory processes. The aim of this study was to evaluate whether different corticosteroids exert any selective effect on the migration of isolated neutrophils. A bilayer of cultured human endothelial and bronchial epithelial cells was used as a model for neutrophil migration through the blood-air barrier. Low spontaneous migration of neutrophils (2.8+/-0.9%, n=8; mean+/-S.E.M.) occurred, while in the absence of any steroid, a migration of 28.5+/-7.6% could be induced by lipopolysaccharide. Pre-incubation during 1 h of epithelial cells with dexamethasone, budesonide, or prednisolone (10(-10)-10(-4) M) showed in all instances a concentration-dependent inhibition following a bell-shaped curve. At 10(-7) M, both dexamethasone and budesonide were on the minimum effect peak of the bell-shaped curve. The peak for prednisolone was found at 10(-8) M. However, when steroid pre-incubation was extended to 4 h, a sigmoid curve was observed, with significant inhibition of migration at concentrations >10(-7) M. Steroids can inhibit neutrophil recruitment through two different pathways with distinct result, depending on the length of incubation time.

The effect of in vitro and in vivo dexamethasone on human neutrophil function

There is a significant fall in PMN chemotaxis to the peptide FMLP in response to increasing concentrations of dexamethasone in vitro. The response fell in a dose related manner from a control value of 53.7 SE +/- 9.6 cells per high power field (cpf) to 47.3 SE +/- 8.1 at 10(-6) M (p less than 0.05) and 24.7 +/- 8.9 at 10(-3) M (p less than 0.025). A similar response was observed for the chemoattractants zymosan activated serum and the sol phase of purulent sputum. The effect was independent of protein synthesis or the period of incubation. Twelve milligrams of dexamethasone taken daily by 6 healthy volunteers resulted in a significant (p less than 0.025) reduction in the chemotactic response of PMN to 10(-8) M FMLP (from 29.5 +/- 1.55 to 13.7 +/- 1.8 cpf) which was apparent within 2 hours of taking the first dose. This effect was sustained for the three days on which dexamethasone was taken but returned to normal 7 days after the last dose had been administered. Dexamethasone therapy had no effect on unstimulated PMN superoxide anion production either in vitro or in vivo. The in vivo effect on neutrophil function occurred at mean serum dexamethasone concentrations of 1.26 (+/- 0.28) X 10(-7) M on day 1, 1.44 (+/- 0.15) X 10(-7) M on day 2 and 1.31 (+/- 0.13) X 10(-7) M on day 3. Thus we conclude that dexamethasone concentration which inhibit PMN chemotaxis in vivo are much lower than those required to exert the same effect in vitro.

The influence of corticosteroids on host defense mechanisms

Glucocorticosteroid hormones affect virtually every tissue type in the body, including tissues of host-defense systems. There is an enormous body of literature concerning specific effects of corticosteroids on host defenses. This literature review examines the affects of corticosteroids on leukocyte kinetics, phagocytic immunity, cell-mediated immunity, and humoral immunity in steroid-resistant species.

The effects of in vivo antibiotics on neutrophil (PMN) activity in rabbits with peritonitis

Antibiotics play an important role in helping the host fight infection; however, the direct cellular effect of antibiotics on polymorphonuclear cells remains undefined. Adherence, chemotaxis, phagocytosis, and superoxide anion production are important steps in the cascade of events initiated by the polymorphonucleocyte in bacterial killing. Previous studies have shown inhibition as well as stimulation of neutrophil antibacterial therapy by antibiotics. Peritoneal and blood polymorphonuclear neutrophils (PMN) respond differently to peritonitis and to external agents. The purpose of this study was to investigate the effects of in vivo clindamycin and netilmicin on infected rabbit peritoneal and blood polymorphonuclear adhesiveness, phagocytosis, chemotaxis, and superoxide anion production. Peritoneal and blood PMNs were obtained from rabbits which had undergone appendiceal devascularization 18 hr earlier: antibiotics were administered intramuscularly 1 hr prior to appendectomy and every 8 hr postoperatively for 5 days; these PMNs were compared to infected rabbits which did not receive antibiotics. Clindamycin and netilmicin in vivo cause significant inhibition of phagocytosis, peritoneal adhesiveness, and, when used in combination, blood adhesiveness and peritoneal superoxide anion production. No effects were seen on chemotaxis. Based on this data we conclude that antibiotics, while vitally important in fighting infections, may in and of themselves be agents of immunosuppression at the cellular level.