HIF-1: a key mediator in hypoxia.

The transcription factor HIF-1 is one of the principal mediators of homeostasis in human tissues exposed to hypoxia. It is implicated in virtually every process of rapid gene expression in response to low oxygen levels. The most common causes of tissue hypoxia are inflammation and/or insufficient circulation or a combination of both. Inflamed tissues and the areas surrounding malignant tumors are characterized by hypoxia and low concentrations of glucose. Serious and generalized inflammation can lead to sepsis and circulatory collapse resulting in acute or chronic tissue hypoxia in various vital organs which induces a rapid homeostatic process in all nucleated cells of affected organs in the human body. Under hypoxic conditions the alpha and beta subunits of HIF-1 make an active heterodimer and drive the transcription of over 60 genes important for cell survival, adaptation, anaerobic metabolism, immune reaction, cytokine production, vascularization and general tissue homeostasis. In addition, HIF-1 plays a key role in the development of physiological systems in fetal and postnatal life. It is also a critical mediator of cancer, lung and cardiovascular diseases. The better understanding of the functions of HIF-1 and the pharmacological modulation of its activity could mean a successful therapeutic approach to these diseases.

The adenosine A2A receptor agonist CGS 21680 fails to ameliorate the course of dextran sulphate-induced colitis in mice.

OBJECTIVE: In this study we investigated the effect of CGS 21680 (2-p-(2-Carboxyethyl)phenethylamino-5-N-ethylcarboxamidoadenosine hydrochloride), an adenosine A2A receptor agonist, in a model of dextran sulphate sodium (DSS)-induced colitis. METHODS: NMRI mice were fed 5 % (w/v) DSS, and were treated intraperitoneally with 0.5 mg/kg CGS 21680 or vehicle for 10 days. Changes of bodyweight, colon length, the incidence of rectal bleeding, levels of macrophage inflammatory protein (MIP)-1alpha, MIP-2, interferon gamma, interleukin (IL)-1beta, IL-12 and tumour necrosis factor-alpha from homogenates of colon biopsies, and the release of [3H]acetylcholine (ACh) from longitudinal muscle strip were determined. RESULTS: DSS significantly decreased bodyweight, colon length, and it increased the incidence of rectal bleeding and levels of MIP-1alpha, MIP-2 and IL-1beta compared to DSS-untreated animals. CGS 21680 had no effect on these changes. No change could be observed in release of ACh in DSS-induced colitis with or without CGS 21680. CONCLUSION: In summary, CGS 21680 is ineffective in ameliorating DSS-induced colitis in mice.