LATE ERYTHROPOIETIN RECEPTOR (EPO-R) AND MULTIDRUG RESISTANCE (MDR-1) OVEREXPRESSION IN AN EXPERIMENTAL STROKE MODEL. A NOVEL LONG-TERM THERAPEUTIC OPPORTUNITY?

MERELLI A; CALTANA LR; RAMOS AJ; BRUSCO ALICIA; LAZAROWSKI A

Buzios, Brasil

Congreso; Ier CongresoIBRO/LARC de Neurociencias de America Latina, Caribe y Península Ibérica. XXIII Congreso de la Sociedad Argentina de Investigación en Neurociencias; 2008

Stroke is a major human health problem inducing long-term disability without therapeutic options, reducing brain aerobic metabolism, loss of function and/or cell death. In focal ischemia, neurons from the penumbra area surrounding infarct core could be rescued with early therapeutics within first 3-6h after stroke. Under hypoxia transient hypoxia-inducible factor-1 (HIF-1a) activation induces Epo/Epo-R system, related with O2 supply and/or cell survival, and neuronal MDR-1 gene expression related with potential impairment to neuroprotective therapeutics. We recently reported high neuronal MDR-1 gene expression 5 days after experimental focal hypoxia induced by direct CoCl2 brain cortical injection, and we have asked if it could be a new obstacle for neuroprotection. Now we ask if other cell-markers as HIF-1 or EPO-R could remains expressed 5 days after injury, offering novels therapeutic stratagems irrespective to the closed therapeutic windows and/or MDR-1 mediated and EPO-R multidrug refractoriness. Our aim was to evaluate the MDR-1, HIF-1a  brain expression in a focal cortical brain hypoxia-ischemia model. In normal adult male Wistar rats (~250g; n=18) saline or sterile CoCl2 (2ìl-50mM) were injected (frontoparietal cortex at Bregma−1.30mm-right hemisphere) by stereotaxic surgical procedure. After 5 days of recovery, animals were anaesthetized (300mg/kg chloral hydrate) and perfused with paraformaldehyde (4% w/v). Coronal 40 ìm thick brain sections corresponding to the nearby area to the saline or CoCl2 injection sites were cut. Immunostaining for MDR-1, HIF-1a and EPO-R were performed in brain slides with specific antibodies. After 5 days of stroke, high expression of HIF-1a and MDR-1 was observed in neurons, astrocytes and vessel with lower EPO-R immunostaining intensity in neurons from penumbra area but several cells shared MDR-1 and EPO-R expression. In controls only MDR-1 was lightly expressed in vessels. We found persistent , MDR-1 and EPO-R (day 5). In spite the potential ,expression of HIF1a farmacoresistance due to MDR-1, EPO-R expression could give a long term therapeutic opportunity in stroke by using Epo. Keywords: Hypoxia; Stroke; MDR-1; HIF-1; Epo-R