Inhibition of NF-kappa B activity by thalidomide through suppression of IkappaB kinase activity.

The sedative and anti-nausea drug thalidomide, which causes birth defects in humans, has been shown to have both anti-inflammatory and anti-oncogenic properties. The anti-inflammatory effect of thalidomide is associated with suppression of cytokine expression and the anti-oncogenic effect with inhibition of angiogenesis. It is presently unclear whether the teratogenic properties of thalidomide are connected in any way to the beneficial, anti-disease characteristics of this drug. The transcription factor NF-kappaB has been shown to be a key regulator of inflammatory genes such as tumor necrosis factor-alpha and interleukin-8. Inhibition of NF-kappaB is associated with reduced inflammation in animal models, such as those for rheumatoid arthritis. We show here that thalidomide can block NF-kappaB activation through a mechanism that involves the inhibition of activity of the IkappaB kinase. Consistent with the observed inhibition of NF-kappaB, thalidomide blocked the cytokine-induced expression of NF-kappaB-regulated genes such as those encoding interleukin-8, TRAF1, and c-IAP2. These data indicate that the therapeutic potential for thalidomide may be based on its ability to block NF-kappaB activation through suppression of IkappaB kinase activity.

Decreased platelet aggregation, increased bleeding time and resistance to thromboembolism in P2Y1-deficient mice.

Platelet activation is characterized by shape change, induction of fibrinogen receptor expression and release of granular contents, leading to aggregation and plug formation. While this response is essential for hemostasis, it is also important in the pathogenesis of a broad spectrum of diseases, including myocardial infarction, stroke and unstable angina. Adenosine 5'-diphosphate (ADP) induces platelet aggregation, but the mechanism for this has not been established, and the relative contribution of ADP in hemostasis and the development of arterial thrombosis is poorly understood. We show here that the purinoceptor P2Y1 is required for platelet shape change in response to ADP and is also a principal receptor mediating ADP-induced platelet aggregation. Activation of P2Y1 resulted in increased intracellular calcium but no alteration in cyclic adenosine monophosphate (cAMP) levels. P2Y1-deficient platelets partially aggregated at higher ADP concentrations, and the lack of P2Y1 did not alter the ability of ADP to inhibit cAMP, indicating that platelets express at least one additional ADP receptor. In vivo, the lack of P2Y1 expression increased bleeding time and protected from collagen- and ADP-induced thromboembolism. These findings support the hypothesis that the ATP receptor P2Y1 is a principal receptor mediating both physiologic and pathological ADP-induced processes in platelets.