Dexamethasone inhibits leukocyte migration through endothelial cells towards smooth muscle cells

Risk factors for chronic biofilm-related infection associated with implanted medical devices

BACKGROUND

The use of implanted medical devices is associated with a small but clinically important risk of foreign body infection. A key question is: why do some patients develop chronic infection associated with an implanted device, but most do not?

AIMS

The literature on patient-specific risk factors for chronic infections associated with five types of implants was surveyed to glean clues about the etiology of these infections.

SOURCES

Data were collected from 47 articles through calendar year 2017 for five categories of device-related infections: cardiovascular implantable electronic devices (CIEDs), hernia meshes, prosthetic hip and knee joints, prosthetic shoulder joints and breast implants.

CONTENT

Important risk factors include immunomodulation/steroid therapy, diabetes, smoking, and renal disease/haemodialysis-findings that point to a critical role of a compromised innate immune response in determining vulnerable subpopulations.

IMPLICATIONS

A model of biofilm-related device infection is presented that posits defects in the innate immune response both systemically and locally, in the immediate vicinity of an abiotic biomaterial. The limitations of in vitro and animal models of chronic device-related infections are discussed in this context as are implications for research and clinical practice.

Effect of high-dose dexamethasone on endothelial haemostatic gene expression and neutrophil adhesion

Glucocorticoid usage especially at high doses is complicated by adverse outcomes such as thrombotic events or acceleration of inflammatory response in conditions like myeloma and osteonecrosis. The mechanism(s) through which high-dose dexamethasone (HDDEXA) causes vascular injury remains unclear. We hypothesized that HDDEXA sensitizes endothelial cells (EC) to the effect of inflammatory mediators and modulates endothelial haemostatic gene expression and leukocyte adhesion. Human umbilical vein endothelial cells (HUVECs) were grown in the absence or presence of HDDEXA and were also tested in the presence or absence of tumor necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS) or thrombin. mRNA and protein expression were measured and the functional consequences of HDDEXA preconditioning on cell adhesion molecules (CAM) were determined by agonist-mediated leukocyte adhesion assay. Treatment with HDDEXA resulted in an increased induction of CAM, tissue factor and von Willebrand factor, while down-regulating thrombomodulin and urokinase. HDDEXA alone had no effect on adhesion but resulted in enhanced TNF-alpha- and LPS-mediated adhesion of neutrophils. Together, these findings suggest that HDDEXA sensitizes HUVEC to the effect of inflammatory mediators and induces a pro-adhesive environment in primary EC. This finding is of importance when glucocorticoid usage is required at therapeutic high doses in patients with or without thrombotic risk factors.

Rat and human aortic smooth muscle cells display differing migration and matrix metalloproteinase activities in response to dexamethasone

OBJECTIVE

The steroid dexamethasone inhibits neointimal hyperplasia development in rats but not in humans. This study investigates the differential effects of dexamethasone on rat and human smooth muscle cell migration and matrix metalloproteinase (MMP) activity.

METHODS

Rat aortic smooth muscle cells were harvested from Sprague-Dawley rats. Human aortic smooth muscle cells were obtained from Clonetics. Boyden chamber migration assays were performed with chemoattractant (platelet-derived growth factor) and varying concentrations of dexamethasone (10(-9) to 10(-5) mol/L). Zymography of culture media was used to assess MMP activity, and Western blot analysis was used for quantification of MMP-2 and tissue inhibitor of MMP-2 (TIMP-2) secretion.

RESULTS

Dexamethasone inhibits rat aortic smooth muscle cell migration in a dose-dependent fashion. An increase in concentrations of dexamethasone does not effect human aortic smooth muscle cell migration. Rat aortic smooth muscle cell MMP-2 activity is inhibited with dexamethasone in a dose-dependent fashion, and human aortic smooth muscle cell MMP-2 activity is unchanged with dexamethasone. MMP-2 secretion is inhibited with dexamethasone in rat aortic smooth muscle cells but remains unaltered in human aortic smooth muscle cells. Dexamethasone increases rat aortic smooth muscle cell TIMP-2 secretion, and human aortic smooth muscle cell TIMP-2 secretion remains constant.

CONCLUSION

Dexamethasone inhibits rat aortic smooth muscle cell migration, MMP-2 activity, and MMP-2 secretion and increases TIMP-2 secretion. These effects are not observed in human aortic smooth muscle cells. These findings may explain why dexamethasone inhibits neointimal hyperplasia in animal models but is ineffective in humans. Inhibition of human smooth muscle cell migration in vitro may be useful in predicting the effectiveness of future therapeutic agents for treatment of neointimal hyperplasia in humans.

Dexamethasone inhibits vascular smooth muscle cell migration via modulation of matrix metalloproteinase activity

BACKGROUND

Dexamethasone (DEX) has been shown to inhibit development of neointimal hyperplasia in rats. We hypothesize that DEX inhibits neointimal hyperplasia by altering matrix metalloproteinase (MMP) activity, resulting in inhibition of smooth muscle cell migration.

METHODS

Rat aortic smooth muscle cells (RASMC) were harvested and cultured for two to four passages. A migration assay was performed in a Boyden chamber with chemoattractant (platelet-derived growth factor) and varying concentrations of DEX (10(-9) to 10(-5) M). The number of migrated cells was counted under light microscopy. Zymography was performed on culture media to assess MMP activity, and Western blotting was performed to assay MMP and levels of tissue inhibitors of MMPs (TIMPs).

RESULTS

DEX progressively inhibited RASMC migration in a dose-dependent fashion. This effect was statistically significant for concentrations of 10(-7) to 10(-5) M (P < 0.0005). Zymography showed that DEX inhibits MMP-2 activity in a dose-dependent manner. Western blots indicated that total MMP-2 secretion was inhibited and that TIMP-2 secretion was increased by DEX.

CONCLUSIONS

DEX inhibits platelet-derived growth factor-induced migration of RASMCs and MMP-2 activity in vitro. Our data suggest that DEX suppresses MMP activity and secretion, resulting in the inhibition of smooth muscle cell migration. This may explain the mechanism by which DEX inhibits neointimal hyperplasia.

Dexamethasone inhibits invasion of murine T cells through cultured fibroblastic monolayers

Despite the wide clinical use of glucocorticoids in the chemotherapy of leukaemia and lymphoma, there have been limited efforts at understanding the effects of these hormones on metastasis formation. The purpose of this study was to investigate the effects of glucocorticoids on the tissue-infiltrating capability of lymphoid cells. Using an in vitro invasion assay, we found that dexamethasone, a synthetic glucocorticoid analogue, inhibited the invasion of a murine T-cell hybridoma through a monolayer of fibroblast-like cells. Even low doses of dexamethasone were effective at inhibiting cellular transmigration (EC50 = 0.4 nM). A maximal decrease was observed after an overnight culture in the presence of dexamethasone. The effect persisted for at least 24 h after removal of the drug and required the binding of the hormone to its intracellular glucocorticoid receptor. Our results suggest that the decreased invasiveness of dexamethasone-treated cells is not the consequence of reduced motility or deficient production of an autocrine factor required for cell migration. This in vitro study suggests that glucocorticoids may act to reduce dissemination of lymphoma cells in vivo.