Animal experiment:

Rats[4]A total of 150 male Sprague-Dawley rats (age, 10-12 weeks; weighing, 280-320 g; are used in the present study. The rats are randomly divided into three groups: Sham-operated group (sham; n=15); the TBI group (TBI; n=35) and the TBI + Harmine-treated group (Harmine; n=35). Harmine is administered immediately following TBI (i.p, 30 mg/kg per day) for up to 5 days. The sham and TBI groups receive equal volumes of 0.9% saline solution (i.p.). The rats are grouped as follows for examination of behavioral recovery: Sham, n=3; TBI, n=7; and Harmine, n=7. Following TBI, the NSS is evaluated at 1, 3 and 5 days. Each rat is assessed by an observer who is blinded to the animal treatment[4].

Harmine is a natural dual-specificity tyrosine phosphorylation-regulated kinase ((DYRK)) inhibitor with anticancer and anti-inflammatory activities.

Harmine is an inhibitor of 5-HT2A, with an Ki of 397 nM[1]. Harmine inhibits tau phosphorylation by DYRK1A by selected DANDYs, with an IC50 of 190 nM[2].Harmine negatively regulates HR by interfering Rad51 recruitment, resulting in severe cytotoxicity in hepatoma cells. Furthermore, NHEJ inhibitor Nu7441 markedly sensitizes Hep3B cells to the anti-proliferative effects of Harmine[3].

It is shown that brain water content is significantly increased in the TBI group. Treatment with Harmine significantly reduces the tissue water content at 1, 3 and 5 days, compared with the TBI group. Harmine treatment significantly reduces the escape latency at 3 and 5 days, compared with the TBI group. Post-TBI administration of Harmine significantly improves the motor function recovery of the rats at 1, 3 and 5 days following TBI, compared with the TBI group without Harmine treatment. The neuronal survival rate in the Harmine-treated group is significantly increased, compared with the TBI group. Administration of Harmine results in marked elevation in the expression of GLT-1, compared with the TBI group. The administration of Harmine significantly reduces the expression of caspase 3, compared with the TBI group[4].

[1]. Glennon RA, et al. Binding of beta-carbolines and related agents at serotonin (5-HT(2) and 5-HT(1A)), dopamine (D(2)) and benzodiazepine receptors. Drug Alcohol Depend. 2000 Aug 1;60(2):121-32. [2]. Neumann F, et al. DYRK1A inhibition and cognitive rescue in a Down syndrome mouse model are induced by new fluoro-DANDY derivatives. Sci Rep. 2018 Feb 12;8(1):2859. [3]. Zhang L, et al. Harmine suppresses homologous recombination repair and inhibits proliferation of hepatoma cells. Cancer Biol Ther. 2015;16(11):1585-92. [4]. Zhong Z, et al. Treatment with harmine ameliorates functional impairment and neuronal death following traumatic brain injury. Mol Med Rep. 2015 Dec;12(6):7985-91.