الفهرس 
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Abstract
Psoriasis is a genetically determined, auto-immune inflammatory, chronic relapsing skin disorder without involvement of known infectious agents or antigens. Clinically, the disease is characterized by scaly and raised erythematous plaques covered by multiple layers of silvery scales. Major characteristics of the disease are hyperproliferative keratinocytes with abnormal differentiation leading to a defective barrier formation, vascular changes, and dermal inflammatory cell infiltration.
Vascular endothelial growth factor (VEGF) also known as vascular permeability factor (VPF) and vasculoprotein, is an endothelial specific growth factor. It is a potent angiogenic agent and very potent hyperpermeability factor being 50000 times more potent than histamine . It belongs to the platelet derived growth factor family. The VEGF family play an integral role in angiogenesis, lymphangiogenesis, and vasculogenesis .
The family of nitric oxide synthase (NOS) enzyme consists of three members: nNos, iNos and eNOS. All of which are expressed in skin. It form nitric oxide which acts as a cellular messenger at low concentrations and plays a decisive role in inflammatory and autoimmune tissue injury when synthesized at high concentrations .
It is indicated that iNos was significantly up-regulated in psoriatic skin and this over expression is the key component of the angiogenic cascade .