Abstract
BACKGROUND AND PURPOSE
We assessed the effects of over-expressing the dual-specific phosphatase, mitogen-activated protein (MAP) kinase phosphatase-2 (MKP-2), in human umbilical vein endothelial cells (HUVECs) on inflammatory protein expression and apoptosis, two key features of endothelial dysfunction in disease.
EXPERIMENTAL APPROACHES
We infected HUVECs for 40 h with an adenoviral version of MKP-2 (Adv.MKP-2). Tumour necrosis factor (TNF)-alpha-stimulated phosphorylation of MAP kinase and protein expression was measured by Western blotting. Cellular apoptosis was assayed by FACS.
KEY RESULTS
Infection with Adv.MKP-2 selectively abolished TNF-alpha-mediated c-Jun-N-terminal kinase (JNK) activation and had little effect upon extracellular signal-regulated kinase or p38 MAP kinase. Adv.MKP-2 abolished COX-2 expression, while induction of the endothelial cell adhesion molecules, intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM), two NF kappa B-dependent proteins, was not affected. However, when ICAM and VCAM expression was partly reduced by blockade of the NF kappa B pathway, Adv.MKP-2 was able to reverse this inhibition. This correlated with enhanced TNF-alpha-induced loss of the inhibitor of kappa B (I kappa B)alpha loss, a marker of NF kappa B activation. TNF-alpha in combination with NF kappa B blockade also increased HUVEC apoptosis; this was significantly reversed by Adv.MKP-2. Protein markers of cellular damage and apoptosis, H2AX phosphorylation and caspase-3 cleavage, were also reversed by MKP-2 over-expression.
CONCLUSIONS AND IMPLICATIONS
Over-expression of MKP-2 had different effects upon the expression of inflammatory proteins due to a reciprocal effect upon JNK and NF kappa B signalling, and also prevented TNF-alpha-mediated endothelial cell death. These properties may make Adv.MKP-2 a potentially useful future therapy in cardiovascular diseases where endothelial dysfunction is a feature.