Ischemia/reperfusion (I/R) is a common injury leading to ischemic stroke. At present, I/R treatment remains limited, highlighting the urgent need for the discovery and development of new protective drugs for brain injury. Here, we investigated the neuroprotective effects of short peptide OM-LV20 previously identified from amphibian against I/R rats. Results showed that intraperitoneal administration of OM-LV20 (20 ng/kg) significantly reduced infarct area formation, improved behavioral abnormalities, and protected cortical and hippocampal neurons against death caused by I/R. Moreover, the underlying molecular mechanism was involved with the regulation of the MAPK and BDNF/AKT signaling pathways, as well as the levels of cyclic adenosine monophosphate, pituitary adenylate cyclase-activating polypeptide receptor, and tryptophan hydroxylase 1. To the best of our knowledge, this research was the first report to describe the neuroprotective effects of an amphibian skin secretion-derived peptide in I/R rats and highlighted OM-LV20 as a promising drug candidate for the development of novel anti-stroke therapies.
Stroke is the second leading cause of death worldwide and first in China due to its high incidence, mortality, disability, and recurrence rates [1]. Globally, nearly 6 million people die of stroke every year, and more than 30 million people are disabled which affects life’s quality seriously [2]. Stroke can be divided into hemorrhagic and ischemic stroke (IS), and IS accounted for 84.4% of the total events [3]. Cerebral vascular occlusion is rarely permanent in human stroke, most people receive spontaneous or thrombolytic therapy reperfusion after IS, i.e., cerebral ischemia/reperfusion (I/R); moreover, the brain damage caused by I/R can be higher than that of simple cerebral IS [4,5]. Currently, the only treatment drug approved for IS worldwide is recombinant tissue plasminogen activator (rt-PA) [6], but based on the huge number of stroke patients diagnosed worldwide (>13.7 million new patients/year), rt-PA alone is often insufficient for successful treatment [7]. Therefore, preventing the occurrence of IS and improving its treatment, especially that of I/R, are important areas of research.
Due to their low molecular weight, high efficiency, and specific targeting ability, certain peptides are reported to have protective effects on brain injury [8]. For example, PcTx1 (from the tarantula Psalmopoeus cambridgei venom) is reported to reduce cortical infarct area by 70% in middle cerebral artery occlusion (MCAO) rats [9]. Hi1a derived from the venom of Hadronyche infensa is reported to significantly reduce cerebral infarct area at 8 h after IS [10]. And intraperitoneal administration of Exendin-4 can significantly reduce brain damage in neonatal hypoxic-ischemic brain injury [11]. Thus, peptides have aroused significant attention in regard to neuroprotective drug discovery and development [8]. At present, novel peptides from amphibian skin secretions are widely recognized as a treasure trove with antimicrobial, antioxidant, wound-healing, and hypoglycemic potency [[12], [13], [14], [15]], however, our knowledge on the neuroprotective potency of peptides from amphibians remains in its infancy.
In previous reports, we identified a peptide OM-LV20 (amino acid sequence: LVGKLLKGAVGDVCGLLPIC) from amphibian skin secretions, and functional results indicated that OM-LV20 accelerated the regeneration of full-thickness wounds and regulated the levels of blood glucose in mice [12,13], which laid solid foundations for us to speculate that the biological effects of OM-LV20 was similar to Exendin-4, and might reduce nerve damage on brain injury as well. In this study, we investigated the neuroprotective effects of OM-LV20 by using rat I/R models and explored the underlying neuroprotective mechanism. To the best of our knowledge, this study was the first report to elucidate the neuroprotective effects of an amphibian skin secretion-derived peptide in I/R rats, thus highlighting OM-LV20 as a promising drug candidate for the development of novel anti-stroke therapies.
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With a purity of >95%, the peptide OM-LV20 (LVGKLLKGAVGDVCGLLPIC) was commercially synthesized by Wuhan Bioyeargene Biotechnology Co. Ltd. (Wuhan, China). The online server PEP-FOLD3 (https://www.frankenthalerfoundation.org Pep-fold3) was used to construct the initial model of the polypeptide, and obtained the final OM-LV20 structure [16].
The stability of OM-LV20 in 4°C, 37°C and in plasma was tested as per previous research [17]. After centrifugation at 12,000×g for
The advanced structure prediction indicated that the main structure of OM-LV20 was the aperiodical coil (Fig.1A and B), and the C-terminal formed a pair of intramolecular disulfide bonds located between C 14–C 20 (Fig.1C).
The stability of OM-LV20 at 4°C, 37°C, and in rat plasma was tested in Fig.1D, E and F. At 4°C, the content of OM-LV20 remained stable even in week 20; but at 37°C, the content of OM-LV20 disappeared in week 16. In addition, the half-life of OM-LV20 in rat plasma was
How to treat stroke and improve outcomes, especially IS nerve injury, are critical research areas currently. In this study, we demonstrated the neuroprotective effects of OM-LV20, a peptide derived from amphibian skin secretions, by using cerebral I/R rat models and the underlying mechanisms were initially explored.
Firstly, the stability of OM-LV20 in rat plasma showed a half-life of 2.843 h (Fig.1F), and it was the reason to establish the I/R model 1 h after OM-LV20 application on day 7, to
The authors declare that there are no conflicts of interest regarding the publication of this paper.
This work was supported by grants from the National Natural Science Foundation of China (81760648, 31670776, and 32060212), Yunnan Applied Basic Research Project-Kunming Medical University Union Foundation (2018FE001(−161), 2019FE001 (−020), and 2019FE001 (−206)), Applied Research Foundation of Diagnosis and Treatment Center of Nervous System Diseases of Yunnan Province (ZX2019-03-05), and Scientific Research Fund Projects from the Department of Education of Yunnan Province (2020Y0113).
2022, Experimental Neurology
Secondly, compared with OM-LV20, a neuroprotective peptide derived from Odorrana margaretae skin, OL-FS13 has a shorter mature peptide sequence (13 vs. 20), and is thus cheaper to synthesize. Finally, although OM-LV20 can alleviate brain injury in I/R rats at a lower dose (20 ng/kg), it plays a role through prophylactic administration, whereas OL-FS13 can be administered after I/R, which undoubtedly improves its clinical application value (Yin et al., 2021). In conclusion, this study reported on a novel neuroprotective peptide (OL-FS13) derived from the skin of the O. livida frog.
These two authors contributed equally to this work.
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