In most acute or chronic inflammatory diseases, frequently caused by inappropriate immune response, cytokines produced by activated lymphocytes and macrophages are largely responsible for severe and often irreversible tissue injury, which may result in permanent functional impairment. The mechanisms of action of the cytokines involved in these processes are complex and only recently the molecular bases of the signal transduction pathways leading to induction of target pro-inflammatory genes have been satisfactorily clarified. However, we still have a limited understanding of the complex interplay among the various signalling pathways and the means by which different transcription factors work in concert to regulate gene expression. Also due to this imperfect knowledge, the availability of effective and safe therapeutics for the control of the pathological effects of cytokines in inflammatory diseases is still limited. In such a context, a major objective of the present project is to assess the inhibitory effect of on cytokine-induced signal transduction pathways and to establish their protective effects against cytokine-induced cell dysfunction and injury. The studies will be performed both in vitro, in cultured cell lines and in primary cell cultures, and in vivo, in animal models of inflammatory diseases. The starting point of this project is the observation that plant extracts, such as green tea (GT) and Hypericum perforatum (St. John’s wort, SJW) extracts, as well as single compounds such as epigallocatechin-3-gallate (EGCG), the main polyphenol component of GT, in recent studies performed in our laboratories have shown a potent anti-interferon (IFN)-γ effect by specifically blocking the activation of the transcription factor STAT-1 induced by this cytokine. Thus, other plant extracts or phytochemicals, screened on the basis of their anti-inflammatory traditional use or their structural affinity with already known active compounds, will be comparatively investigated. Extracts resulted to be active will be further fractionated by chromatographic techniques and individual compounds, identified and characterized by spectroscopic and spectrometric methods, will be submitted to biological tests. We will also consider that STAT-1 usually acts in combination with other transcription factors, such as NF-kB, activated by cytokines like IL-1β and TNF-α, likewise implicated in the pathogenesis of severe inflammatory processes. Thus, in this project, the effects of a number of natural compounds on transduction signalling pathways induced by various cytokines (IFN-γ; TNF-α; IL-1β, IL-6) will be studied in various cell types, by evaluating: a) the activation of specific kinases (JAK, p38, JNK, ERK1/2) and transcription factors (STAT-1, STAT-3, NF-kB, AP-1); b) the expression of several target genes involved in sustaining the inflammatory process and triggering apoptosis; c) the development of cell damage (apoptosis, necrosis, functional changes). Moreover, in vivo experiments carried out in animal models of ischemia/reperfusion-induced heart injury, acute and chronic asthma and type 1 diabetes will assess the ability of the vegetal compounds to prevent, delay or attenuate the development of these inflammatory conditions. A better knowledge of the molecular mechanisms responsible for cytokine-induced cell damage and the demonstration that at least some of such mechanisms, including that involved in the triggering of the response, could be the specific targets of new safe pharmacological tools, will be very helpful for the control of many inflammatory processes and the prevention or limitation of tissue injury.