Methylprednisolone Stiffens Aortas in Lipopolysaccharide-Induced Chronic Inflammation in Rats

Introduction: Glucocorticoids are commonly used as therapeutic agents in many acute and chronic inflammatory and auto-immune diseases. The current study investigated the effects of methylprednisolone (a synthetic glucocorticoid) on aortic distensibility and vascular resistance in lipopolysaccharide-induced chronic inflammation in male Wistar rats. Methods: Chronic inflammation was induced by implanting a subcutaneous slow-release ALZET osmotic pump (1 mg kg(-1) day(-1) lipopolysaccharide) for either 2 or 4 weeks. Arterial wave transit time (t) was derived to describe the elastic properties of aortas using the impulse response function of the filtered aortic input impedance spectra. Results: Long-term lipopolysaccharide challenge enhanced the expression of advanced glycation end products (AGEs) in the aortas. Lipopolysaccharide also upregulated the inducible form of nitric oxide synthase to produce high levels of nitric oxide (NO), which resulted in vasodilation, as evidenced by the fall in total peripheral resistance (R-p). However, lipopolysaccharide challenge did not influence the elastic properties of aortas, as shown by the unaltered iota. The NO-mediated vascular relaxation may counterbalance the AGEs-induced arterial stiffening so that the aortic distensibility remained unaltered. Treating lipopolysaccharide-challenged rats with methylprednisolone prevented peripheral vasodilation because of its ability to increase R-p. However, methylprednisolone produced an increase in aorta stiffness, as manifested by the significant decline in iota. The diminished aortic distensibility by methylprednisolone paralleled a significant reduction in NO plasma levels, in the absence of any significant changes in AGEs content. Conclusion: Methylprednisolone stiffens aortas and elastic arteries in lipopolysaccharide-induced chronic inflammation in rats, for NO activity may be dominant as a counteraction of AGEs.