Anti-apoptotic activity of ETB receptor agonist, IRL-1620, protects neural cells in rats with cerebral ischemia

Abstract

Endothelin-B receptor agonist, IRL-1620, provides significant neuroprotection following cerebral ischemia in rats. Whether this neuroprotection is due to inhibition of apoptosis is unknown. IRL-1620-treated rats following permanent middle cerebral artery occlusion (MCAO) showed significant improvement in neurological and motor functions along with a decrease in infarct volume at 24 h (−81.3%) and day 7 (−73.0%) compared to vehicle group. Cerebral blood flow (CBF) significantly improved in IRL-1620-treated animals compared to vehicle by day 7 post MCAO. IRL-1620-treated rats showed an increase in phospho-Akt and decrease in Bad level 7 h post-occlusion compared to vehicle, while Akt and Bad expression was similar in cerebral hemispheres at 24 h post-MCAO. The phospho-Bad level was lower in vehicle- but not in IRL-1620-treated rats at 24 h. Anti-apoptotic Bcl-2 expression decreased, while pro-apoptotic Bax expression increased in vehicle-treated MCAO rats, these changes were attenuated (P < 0.01) by IRL-1620. Mitochondrial membrane-bound Bax intensity significantly decreased in IRL-1620 compared to vehicle-treated MCAO rats. IRL-1620 treatment reduced (P < 0.001) the number of TUNEL-positive cells compared to vehicle at 24 h and day 7 post MCAO. The results demonstrate that IRL-1620 is neuroprotective and attenuates neural damage following cerebral ischemia in rats by increasing CBF and reducing apoptosis.

Sovateltide (IRL-1620) activates neuronal differentiation and prevents mitochondrial dysfunction in adult mammalian brains following stroke

“…We have consistently shown in our preclinical studies carried out using MCAO rat model [10][11][12][13] , that sovateltide treatment helps in restoration of blood flow, modulation of apoptosis and improvement in neurological and motor functions after cerebral ischemic stroke. These observations indicate a role of ETBR in tissue healing after acute ischemic damage in the brain after stroke.…”

“…Additionally, animals receiving sovateltide displayed increased number of proliferating cells as well as NGF + cells in the infarcted brain tissues 12 . Recently, we confirmed sovateltide as a pro-survival and anti-apoptotic agent in ischemic brains of MCAO rats 13 . To assess its safety and efficacy in human subjects, we performed a phase I clinical trial (CTRI/2016/11/007509) in healthy human volunteers 14 and a multicentric, randomized, double-blind, parallel, saline-controlled efficacy clinical trial (NCT04046484) in patients with acute cerebral ischemic stroke 15 .…”

“…We permanently occluded the middle cerebral artery to create focal ischemic stroke in the right cerebral hemisphere of the rat brain. This procedure of MCAO interrupts the blood flow mainly in the right hemisphere of the brain; however, the partial ischemic effects on the contralateral cerebral hemisphere due to interference in collateral blood flow is possible 13 . We treated one set of MCAO rats at 4, 6, and 8 h and sacrificed them at 24 h post MCAO, while another set of rats were treated similarly at day 0, 3 and 6 and sacrificed at day 7.…”

“…Another aspect of our study was to explore the role of mitochondria in survival of NPCs and neuronal function restoration in stroked brain after sovateltide treatment. Our recent study has demonstrated that sovateltide treatment could modulate the interaction of apoptotic protein Bax to mitochondrial membrane 13 , which is a critical event in mitochondria mediated cell death 44 , 45 . These observations suggested that sovateltide mediated activation of ETBR influenced the mitochondrial fate.…”

“…We used the immunofluorecence technique to detect expression of mitochondrial fission (DRP1) and fusion (MFN2) markers in rat brain tissues and to examine the expression of NeuroD1 and NeuN in cultured NPCs. The tissue immunofluorescence technique was followed as described earlier 7,13 . In brief, right brain hemisphere was dissected as depicted in Fig.…”