OHSU

Stenzel-Poore Lab

overview

My research program involves injury, inflammation and neuroprotection in stroke. We are interested in how the brain normally responds to cerebral ischemia (stroke) and how we can improve that response by pretreatment, i.e. preconditioning, with various stimuli. Some preconditioning stimuli include brief periods of ischemia, and low doses of bacterial- or viral-associated molecules such as endotoxin (lipopolysaccharide, LPS) and non-methylated CpG oligodeoxynucleotides (ODNs). Via microarray profiling, we have discovered that the brain’s response to stroke injury is completely reprogrammed in the setting of prior preconditioning. Such reprogramming leads to a novel response to cerebral ischemia, which is dominated by the expression of anti-inflammatory cytokines that are known to be neuroprotective (e.g. TGFβ and IFNβ). We are striving to identify (1) the essential molecular mediators common among these models of preconditioning and (2) the essential molecular mediators specific to each individual preconditioning paradigm. These studies have flourished via a productive collaboration with Dr. Roger Simon, a neuroscientist and neurologist at The Dow Neurobiology Institute in Portland, Oregon. Together, we hope to identify fundamental endogenous pathways responsible for an improved cellular and systemic ischemic response. Our primary goal is to uncover novel therapeutic targets for stroke.

Our studies have recently advanced to a very relevant preclinical model of mammalian stroke. This work involves collaborations with scientists from the Advanced Imaging Center at OHSU, the Oregon National Primate Research Center and the Dow Neurobiology Institute. Collectively, we have begun a translational research program around neuroprotection in stroke using candidate therapeutics.

in detail

Preconditioning with TLR9

C57BL/6 (males, 6-10/dose) received various doses of CpG 1826 (5-40ug; i.p.) 72 hr prior to ischemic challenge (60 min MCAO). Click to enlarge.

We have begun to elucidate the genomic basis of preconditioning using microarray gene profiling of ischemic brain in a mouse model of stroke. We have discovered that the response to stroke injury is completely reprogrammed in the setting of prior preconditioning. Such reprogramming leads to a novel response to stroke injury, which is dominated by expression of anti-inflammatory cytokines that are known to be neuroprotective (e.g. TGF-b and IFN-b) We also know that in addition to the brain, the systemic response to preconditioning influences neuroprotection; thus, we have recently turned our attention to the genomic and proteomic responses to preconditioning in blood leukocytes. These studies require informative strategies in computational biology to enrich our ability to define potential neuroprotectants and associated pathways. We collaborate with scientists at Pacific Northwest National Laboratories (PNNL) to develop specialized software that has increased our ability to create meaningful models of pathways and mediators of neuroprotection in stroke.


Proconditioning reprograms the genetic response to ischemic injury.

Preconditioning reprograms the genetic response to ischemic injury. Shown are the number of genes increased or decreased in the ischemic hemisphere as compared to the non-ischemic hemisphere. Click to enlarge.

Our approach to find endogenous neuroprotectants that are induced by ischemic preconditioning has led us to the discovery of a novel mediator that protects against stroke injury. We have found that osteopontin, a large secreted glycoprotein, which is known to be involved in cell survival,  is involved in the protective response to stroke injury. We have now shown that osteopontin administration to mice at the time of a stroke reduces injury. Osteopontin treatment of cultured neurons also enhances neuronal survival using modeled ischemia in vitro. We have shown that activation of Akt and p42/p44 MAPK cascades is involved in osteopontin-mediated protection, which supports our view that protection involves integrin receptor ligation. Osteopontin offers important advantages to the development of a stroke therapeutic because it is a natural biological product made in the body and acts via cell surface molecules (integrins) important in cell survival. We are currently funded to enhance the efficacy of OPN as a neuroprotectant and determine efficient drug delivery systems that may be applicable to patients suffering from acute stroke injury.


LPS preconditioning alters stroke-induced TLR4 signaling

LPS preconditioning alters stroke-induced TLR4 signaling: Pre-stroke induction of MyD88 dependent pathway inibitors shunts stroke-induced TLR4 signaling down the MyD88 independent pathway. Click to enlarge.

Our approach to find endogenous neuroprotectants that are induced by ischemic preconditioning has led us to the discovery of a novel mediator that protects against stroke injury. We have found that osteopontin, a large secreted glycoprotein, which is known to be involved in cell survival,  is involved in the protective response to stroke injury. We have now shown that osteopontin administration to mice at the time of a stroke reduces injury. Osteopontin treatment of cultured neurons also enhances neuronal survival using modeled ischemia in vitro. We have shown that activation of Akt and p42/p44 MAPK cascades is involved in osteopontin-mediated protection, which supports our view that protection involves integrin receptor ligation. Osteopontin offers important advantages to the development of a stroke therapeutic because it is a natural biological product made in the body and acts via cell surface molecules (integrins) important in cell survival. We are currently funded to enhance the efficacy of OPN as a neuroprotectant and determine efficient drug delivery systems that may be applicable to patients suffering from acute stroke injury.