In addition to directly causing neuronal damage ischemic stroke elicits a delayed neuroinflammatory response that is characterized by lymphocyte infiltration, hyperthermia and robust microglia activation. "Reactive" microglia in particular contribute to this "secondary damage" by producing inflammatory cytokines, reactive oxygen species, NO, and cyclooxygenase-2 reaction products. However, activated microglia might also be neuroprotective by releasing neurotrophic factors and phagocytosing cellular debris. The goal of microgliatargeted therapies therefore should be to reduce the neurotoxic effects of activated microglia while at the same time maintaining their beneficial functions. We here hypothesize, that blockers of the microglial K+ channels Kv1.3 and KCa3.1 might be able to do exactly this based on the preliminary data presented in this application. We previously designed potent and selective small molecule inhibitors for both channels, PAP-1 for Kv1.3 and TRAM-34 for KCa3.1, and demonstrated that these compounds can prevent or treat various autoimmune diseases and inflammatory conditions in rodents such as contact dermatitis, type-1 diabetes, inflammatory bowel disease, atherosclerosis and EAE. More recently we made the exciting observation that our KCa3.1 blocker TRAM-34 reduces infarct area and neurological deficit scores following ischemic stroke in rats even if treatment is commenced 12 hours after reperfusion. Another strong rationale for our study is a report that TRAM-34 does not prevent microglia from phagocytosing damaged neurons but increases the number of surviving retinal ganglion cells following optic nerve transection in rats by reducing the production and/or secretion of neurotoxic molecules in the retina. Taken together with previous work from our laboratory and other groups implicating both Kv1.3 and KCa3.1 in microglia mediated neuronal killing, these results suggest Kv1.3 and KCa3.1 as novel targets for CNS pathologies involving inflammation. With the help of this grant we therefore intend to test the hypothesis that both channels constitute novel targets for the treatment of stroke.
Under Aim -1 we will more rigorously evaluate Kv1.3 and KCa3.1 as targets for stroke by testing the effect of both pharmacological blockade and genetic deletion in reperfusion MCAO and by performing parallel in vitro studies to investigate the role Kv1.3 and KCa3.1 in microglia functions.
Under Aim -2 we will use our expertise in medicinal chemistry to design a less lipophilic and more brain penetrant small molecule Kv1.3 inhibitor than our existing lead compound PAP-1 (IC50 2 nM). We further will resynthesize a brain-penetrant KCa3.1 inhibitor, which was abandoned by Bayer, when the company pulled out of stroke research.
Under Aim -3 we will directly compare the new Kv1.3 and KCa3.1 blockers to minocycline in a 4-week trial by assessing in vivo cytokine production, neurogenesis and functional recovery. As a first step towards translating our findings to humans, we will further obtain brain sections from stroke patients and controls and perform immunohistochemistry for KCa3.1, Kv1.3, and microglia activation markers.

Public Health Relevance

Microglia are cells of the immune system, that reside in the brain, and have been shown to significantly contribute to the delayed inflammatory damage following ischemic stroke. With the help of this grant we will test whether small molecule inhibitors of two potassium channels that are involved in microglia activation constitute therapeutic targets for the treatment of stroke.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM076063-07
Application #
8499351
Study Section
Brain Injury and Neurovascular Pathologies Study Section (BINP)
Program Officer
Nie, Zhongzhen
Project Start
2006-07-01
Project End
2015-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
7
Fiscal Year
2013
Total Cost
$300,402
Indirect Cost
$102,577
Name
University of California Davis
Department
Pharmacology
Type
Schools of Medicine
DUNS #
047120084
City
Davis
State
CA
Country
United States
Zip Code
95618
Grimaldi, A; D'Alessandro, G; Golia, M T et al. (2016) KCa3.1 inhibition switches the phenotype of glioma-infiltrating microglia/macrophages. Cell Death Dis 7:e2174
D'Alessandro, Giuseppina; Grimaldi, Alfonso; Chece, Giuseppina et al. (2016) KCa3.1 channel inhibition sensitizes malignant gliomas to temozolomide treatment. Oncotarget 7:30781-96
Feske, Stefan; Wulff, Heike; Skolnik, Edward Y (2015) Ion channels in innate and adaptive immunity. Annu Rev Immunol 33:291-353
Hong, Liang; Singh, Vikrant; Wulff, Heike et al. (2015) Interrogation of the intersubunit interface of the open Hv1 proton channel with a probe of allosteric coupling. Sci Rep 5:14077
Roach, Katy M; Feghali-Bostwick, Carol; Wulff, Heike et al. (2015) Human lung myofibroblast TGFβ1-dependent Smad2/3 signalling is Ca(2+)-dependent and regulated by KCa3.1 K(+) channels. Fibrogenesis Tissue Repair 8:5
Chen, Yi-Je; Nguyen, Hai M; Maezawa, Izumi et al. (2015) The potassium channel KCa3.1 constitutes a pharmacological target for neuroinflammation associated with ischemia/reperfusion stroke. J Cereb Blood Flow Metab :
Jin, Lee-Way; Horiuchi, Makoto; Wulff, Heike et al. (2015) Dysregulation of glutamine transporter SNAT1 in Rett syndrome microglia: a mechanism for mitochondrial dysfunction and neurotoxicity. J Neurosci 35:2516-29
Chen, Yi-Je; Wallace, Breanna K; Yuen, Natalie et al. (2015) Blood-brain barrier KCa3.1 channels: evidence for a role in brain Na uptake and edema in ischemic stroke. Stroke 46:237-44
Roach, Katy M; Wulff, Heike; Feghali-Bostwick, Carol et al. (2014) Increased constitutive αSMA and Smad2/3 expression in idiopathic pulmonary fibrosis myofibroblasts is KCa3.1-dependent. Respir Res 15:155
Chhabra, Sandeep; Chang, Shih Chieh; Nguyen, Hai M et al. (2014) Kv1.3 channel-blocking immunomodulatory peptides from parasitic worms: implications for autoimmune diseases. FASEB J 28:3952-64

Showing the most recent 10 out of 47 publications