Neuroprotective pentapeptide CN-105 improves functional and histological outcomes in a murine model of intracerebral hemorrhage

Abstract

Presently, no pharmacological treatments have been demonstrated to improve long-term functional outcomes following intracerebral hemorrhage (ICH). Clinical evidence associates apolipoprotein E (apoE) genotype with ICH incidence and outcome. While apoE modifies neuroinflammatory responses through its adaptive role in glial downregulation, intact apoE holoprotein is too large to cross the blood-brain barrier (BBB). Therefore, we developed a 5-amino acid peptide - CN-105 - that mimics the polar face of the apoE helical domain involved in receptor interactions. In the current study, we investigated the therapeutic potential of CN-105 in a mouse model of ICH. Three doses of CN-105 (0.05 mg/kg) was administered by tail vein injection within 24 hours after ICH induction. Functional assessment showed durable improvement in vestibulomotor performance after CN-105 treatment, as quantified by increased Rotarod latencies on Days 1-5 post-ICH, and long-term improvement in neurocognitive performance, as quantified by reduced Morris water maze latencies on Days 29-32 post-ICH. Further, brain water content was significantly reduced, neuroinflammation was decreased and hippocampal CA3 neuronal survival was increased, although hemorrhage volume was not affected by CN-105. We concluded, therefore, that pentapeptide CN-105 improved short- and long-term neurobehavioral outcomes in a murine model of ICH, suggesting therapeutic potential for patients with acute ICH.

Figures

Figure 1. Brain and plasma pharmacokinetic analysis of CN105 demonstrated a terminal plasma half-life of 27 minutes, with AUC0–60 in plasma of 1253 min*fmol/ul, and in brain 548 min*fmol/ul.

Figure 2. Hemorrhage volume was similar between CN-105- and saline-treated mice.

CN-105 did not reduce hemorrhage volume as assessed by SWI -MRI (A,B) images or by H&E staining (A,C). (n = 3–4/group).

Figure 3. Brain water content was reduced in CN-105 mice at 24 hours post ICH.

(*p < 0.05; n = 6–8/group).

Figure 4. Short-term function improved in CN-105 animals over 5 days following ICH.

CN-105 mildly, but not significantly, improved recovery of neurobehavioral function (A). CN-105 significantly improved recovery of vestibulomotor function, based on rotarod testing (B). (n = 14/group).

Figure 5. Neurocognitive function showed long-term improvement in CN-105 mice, based on MWM testing.

(A) Latencies in CN-105-treated mice were lower and learning curves were steeper; (B) slope of learning curve presented as absolute value) over 4 days of testing, compared to saline-treated group. (*p < 0.05; n = 14/group).

Figure 6. CN-105 reduces brain microglial activation after ICH.

(A) Representative images of F4/80-labelled microglia in ipsilateral hippocampi at 5 days after ICH in mice treated with vehicle or CN-105. (B) Stereological analysis showed that CN-105 treatment significantly decreased the number of F4/80-positive cells in the ipsilateral hippocampi. ** p < 0.01, compared to vehical group, n = 3–4.

Figure 7. Hippocampal CA3 neuronal survival increased in CN-105 mice, based on NeuN staining and stereology at 33 days post ICH.

NeuN-positive cells were counted in ipsilateral CA3 and dentate gyrus polymorphic region of dorsal hippocampus and striatum (A). Ipsilateral NeuN-positive cell numbers were significantly increased in the CA3 region of the dorsal hippocampus after injury, compared to vehicle-treated counterparts (B). (**p < 0.01; n = 7/group).