Centrifugal Force Induces Human Ligamentum Flavum Fibroblasts Inflammation Through Activation of JNK and p38 Pathways

Abstract

Inflammation has been proposed to be an important causative factor in ligamentum flavum hypertrophy. However, the mechanisms of mechanical load on inflammation of ligamentum flavum remain unclear. In this study, we used an in vitro model of human ligamentum flavum fibroblasts subjected to centrifugal force to elucidate the effects of mechanical load on cultured human ligamentum flavum fibroblasts; we further studied its molecular and biochemical mechanisms. Human ligamentum flavum fibroblasts were obtained from six patients undergoing lumbar spine surgery. Monolayer cultures of human ligamentum flavum fibroblasts were subjected to different magnitudes of centrifugal forces. Cell viability, cell death, biochemical response, and molecular response to centrifugal forces were analyzed. It was found that centrifugal stress significantly suppressed cell viability without inducing cell death. Centrifugal force at 67.1 g/cm² for 60 min significantly increases the production of prostaglandin E2 and nitric oxide as well as gene expression of proinflammatory cytokines, including interleukin (IL)-1α, IL-1β and IL-6, showed that centrifugal force-dependent induction of cyclooxygense-2 and inducible NO synthase required JNK and p38 mitogen-activated protein kinase, but not ERK 1/2 activities. This study suggested that centrifugal force does induce inflammatory responses in human ligamentum flavum fibroblasts. The activation of both JNK and p38 mitogen-activated protein kinase mechanotransduction cascades is a crucial intracellular mechanism that mediates cyclooxygense-2/prostaglandin E2 and inducible NO synthase/nitric oxide production.

• centrifugal force
• human ligamentum flavum fibroblasts
• inflammation
• prostaglandins
• nitric oxide
• cyclooxygenase
• mitogen-activated protein kinases

Acknowledgments

We acknowledge the National Science Council, Taiwan, and Research Fund of Taipei City Hospital, Taipei, Taiwan, for their funding assistance for this work. We also thank the staff of the Second Core Lab, Department of Medical Research, National Taiwan University Hospital, for technical support during the study and John DeRisco for his assistance in the editorial preparation of this manuscript. This research was supported and sponsored by National Science Council and Taipei City Hospital (Taiwan).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.