New Releases by Omar Mohamed

Simulation of sunburn reaction has been used as a model of skin inflammation. In this context, skin innervation has been shown to play an important role in mo dulating the inflammatory reaction in the skin. The aim of this study is to gain insight into the role of cutaneous sensory innervation during acute and chronic inflammatory resp onses induced by UV. Sunlamps emitting mainly midrange UV radiation (UVB) have been implemented extensively to study skin injury in animal models due to their ease of use and effectiveness. Increased pain sensitivity and upregulation of pro-inflammato ry cytokines characterize most inflammatory responses. Release of neuropeptides by the primary afferent fibers innervating the inflamed area modulates such response an d thus the process is referred as neurogenic inflammation. In this study, a rat model was designed to assess the effect of localized UVB exposure (250 mj/cm2) on the nociceptive response and release of proinflammatory cytokines. In addition, SKH/1 hr hairless mice were used for chronic UVB irradia tion with a dose of 180 mj/cm2 three times per week for two consecutive weeks and carefully observed for the induction of skin tumors. This work showed a biphasic hyperalgesia with an early phase (1-3h) after the exposure and a late phase (48h) restricted to the irradiated paw only. The decre ase in pain thresholds upon thermal stimulation were not observed after the ablation of the capsaicin sensitive primary afferents (CSPA-fibers). However, the animals show increased sensitivity to non-noxious mechanical and cold stimuli. Chronic UVB treatment resulted in the formation of epidermal skin tumors as compared to control mice. Selective ablation of CSPA fibers reduced the incidenc e of skin lesions. These results demonstrate a key role of cutaneous sensory nerves in acute and chronic inflammatory reactions induced by UVB exposure.