Lack of Neuroprotection of Inhibitory Peptides Targeting Jun/JNK after Transient Focal Cerebral Ischemia in Spontaneously Hypertensive Rats

Abstract

In this study, we have assessed the ability of two TAT-fused peptides PYC36D-TAT and JNKI-1D-TAT (JNKI-1 or XG-102), which respectively inhibit jun proto-oncogene (c-Jun) and c-Jun N-terminal kinase (JNK) activation, to reduce infarct volume and improve functional outcome (adhesive tape removal) after transient focal cerebral ischemia in Spontaneously Hypertensive (SH) rats. PYC36D-TAT and JNKI-1D-TAT peptide batches used for experiments were tested in vitro and protected cortical neurons against glutamate excitotoxicity. Rats were treated intravenously with three different doses of PYC36D-TAT (7.7, 76, or 255 nmol/kg), JNKI-1D-TAT (255 nmol/kg), D-TAT peptide (255 nmol/kg), or saline (vehicle control), 10 minutes after reperfusion after 90 minutes of middle cerebral artery occlusion (MCAO). Contrary to other stroke models, no treatment significantly reduced infarct volume or improved functional score measurements compared with vehicle-treated animals when assessed 48 hours after MCAO. Additionally, assessment of the JNKI-1D-TAT peptide, when administered 1 or 2 hours after reperfusion after 90 minutes of MCAO, also did not improve histological or functional outcomes at 48 hours after occlusion. This study is the first to evaluate the efficacy of PYC36D-TAT and JNKI-1D-TAT using the SH rat, which has recently been shown to be more sensitive to AMPA receptor activation rather than to NMDA receptor activation after cerebral ischemia, and which may have contributed to the negative findings.

Peptides targeting the mitogen-activated protein kinase pathway (JNK/Jun) fail to reduce infarct volume after permanent MCAO in Sprague Dawley rats

“…The negative finding is inline with our previous study assessing the neuroprotective action of the JNKI-1D-TAT and PYC36D-TAT peptides in a rat transient focal cerebral ischemia stroke model (Gow et al, 2011). In the present study, our dose range for JNKI-1D-TAT was 250 -1500 nmol/kg and for PYC36D-TAT 50 -1500 nmol/kg, which at least for the former peptide is within the range used in previous positive rodent stroke studies.…”

“…It should also be mentioned, that we have previously reported a lower IC50 value for PYC36D-TAT (1.3µmol/L) compared to JNKI-1D-TAT (IC50: 2.1µmol/L) in glutamate neuronal excitotoxicity model (Meade et al, 2010a). As we reported in our previous negative study (Gow et al, 2011), the lack of any significant neuroprotective with these peptides, especially JNKI-1D-TAT, is unexpected given their previously reported in vitro and/or in vivo positive J Exp Stroke Transl Med (2012) 5(1): 22-30 Association of Experimental Stroke and Translational Medicine neuroprotective effects (Borsello et al, 2003;Hirt et al, 2004;Gao et al, 2005;Repici et al, 2007;Esneault et al, 2008;Soriano et al, 2008;Wiegler et al, 2008;Liu et al, 2010;Benakis et al, 2010;Meade et al, 2010ab;Craig et al, 2011;Vaslin et al, 2011; Table 1). …”

Combined Antiapoptotic and Antioxidant Approach to Acute Neuroprotection for Stroke in Hypertensive Rats

“…16 After tMCAO in spontaneously hypertensive rats, however, no such neuroprotection was seen. 17 This was attributed, in part, to the predominance of AMPA (a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)-rather than NMDA (N-methyl-D-aspartate)-activated ischemic brain injury in the SHR. 17 One further reason may be the more severe ischemic insult induced by MCAO in SHR (and SHRSP), leading to a greater contribution of necrotic to apoptotic cell death.…”

“…17 This was attributed, in part, to the predominance of AMPA (a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)-rather than NMDA (N-methyl-D-aspartate)-activated ischemic brain injury in the SHR. 17 One further reason may be the more severe ischemic insult induced by MCAO in SHR (and SHRSP), leading to a greater contribution of necrotic to apoptotic cell death. This could result in reduced efficacy of drugs targeting the JNK signaling pathway and highlights once again, the importance of including stroke associated comorbidities in preclinical studies.…”

Comparison of infarct volume and behavioral deficit in Wistar Kyoto and spontaneously hypertensive rat after transient occlusion of the middle cerebral artery

“…SHR rats have a genetic background of WKY and suffer from early hypertension, hyperinsulinemia, hypertriglyceridemia, and hypercholesteremia (Iritani et al 1977; Swislocki and Tsuzuki 1993). Consequently, the SHR strain recently is more frequently used in stroke and cardiovascular research (Gow et al 2011; Wang et al 2012). …”