Neuroprotective Efficacy from a Lipophilic Redox-Modulating Mn(III) N-Hexylpyridylporphyrin, MnTnHex-2-PyP: Rodent Models of Ischemic Stroke and Subarachnoid Hemorrhage

Abstract

Intracerebroventricular treatment with redox-regulating Mn(III) Nhexylpyridylporphyrin (MnPorphyrin) is remarkably efficacious in experimental central nervous system (CNS) injury. Clinical development has been arrested because of poor blood-brain barrier penetration. Mn(III) meso-tetrakis (N-hexylpyridinium-2-yl) porphyrin (MnTnHex-2-PyP) was synthesized to include four six-carbon (hexyl) side chains on the core MnPorphyrin structure. This has been shown to increase in vitro lipophilicity 13,500-fold relative to the hydrophilic ethyl analog Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP). In normal mice, we found brain MnTnHex-2-PyP accumulation to be ϳ9-fold greater than MnTE-2-PyP 24 h after a single intraperitoneal dose. We then evaluated MnTnHex-2-PyP efficacy in outcome-oriented models of focal cerebral ischemia and subarachnoid hemorrhage. For focal ischemia, rats underwent 90-min middle cerebral artery occlusion. Parenteral MnTnHex-2-PyP treatment began 5 min or 6 h after reperfusion onset and continued for 7 days. Neurologic function was improved with both early (P ϭ 0.002) and delayed (P ϭ 0.002) treatment onset. Total infarct size was decreased with both early (P ϭ 0.03) and delayed (P ϭ 0.01) treatment. MnTnHex-2-PyP attenuated nuclear factor B nuclear DNA binding activity and suppressed tumor necrosis factor-␣ and interleukin-6 expression. For subarachnoid hemorrhage, mice underwent perforation of the anterior cerebral artery and were treated with intraperitoneal MnTnHex-2-PyP or vehicle for 3 days. Neurologic function was improved (P ϭ 0.02), and vasoconstriction of the anterior cerebral (P ϭ 0.0005), middle cerebral (P ϭ 0.003), and internal carotid (P ϭ 0.015) arteries was decreased by MnTnHex-2-PyP. Side-chain elongation preserved MnPorphyrin redox activity, but improved CNS bioavailability sufficient to cause improved outcome from acute CNS injury, despite delay in parenteral treatment onset of up to 6 h. This advance now allows consideration of MnPorphyrins for treatment of cerebrovascular disease.

SOD Therapeutics: Latest Insights into Their Structure-Activity Relationships and Impact on the Cellular Redox-Based Signaling Pathways

“…While thus far we have understood the radioprotective effects as resulting from scavenging reactive species, rising number of data argue that perhaps mild pro-oxidative action of MnP may predominate. The oxidation of NF-jB (which controls HIF-1a, and its genes) by MnP would prevent excessive inflammation, secondary oxidative stress and result in prevention of extensive oxidative damage of biological targets (208,209,(236)(237)(238)(239)(240)278). Data on rat kidney ischemia/reperfusion indicate that MnP can also up-regulate endogenous antioxidative defenses (52, 75).…”

“…In subsequent reoxidation of MnP with O 2 or O 2 $ -, and oxidation of ascorbate radical to dehydroascorbate, the peroxide is produced. MnP can employ peroxide and/or GSH to inactivate nuclear factor jB (NF-jB) (82,125,127,238,240), suppress mitochondrial respiration (124) and glycolysis (70,124), or induce adaptive responses (52, 75). Such pro-oxidative actions agree well with what Forman et al recently put forward as the mechanism of action of natural antioxidants (89).…”

“…The investigations of the effect of MnPs on the up-regulation of numerous cytokines (33) made it clear that either direct reactions with reactive species (which supposedly signal the start of the cellular transcription) or direct reactions with signaling proteins may be involved. The driving force for understanding such observations was the fact that MnPs were as efficient in reducing mouse or rat infarct volume when given at early (6 min) or at late time points (90 min or 6 h) after reperfusion (238)(239)(240). Our knowledge at the time when the observation was made would predict that only immediate infusion of porphyrin into the brain at the time of reperfusion (the moment of peak production of reactive species) would ameliorate the primary oxidative damage.…”

“…Thus, we embarked on a PK journey. HPLC/fluorescence and later LCMS/MS methods were developed for each individual compound (140,177,238,250,252,254,288), which supported the comprehensive biodistribution studies. We have also expanded our synthetic efforts to increase porphyrin bioavailability.…”

Xenon Neuroprotection in Experimental Stroke

“…[23][24][25] General status, simple motor deficit, complex motor deficit, and sensory deficit were scored. 24 The score given to each animal at the completion of testing was the sum of the four individual scores with 0 being the minimum (best) score and 48 the maximum possible (worst) score.…”