Effects of hydroxychloroquine and therapeutic hypothermia onneuroprotection and behavioral patterns in rats with neonatal hypoxic ischemic encephalopathy

Perinatal hypoxic ischemic brain injury (HIBI) is one of the most important causes of mental reperfusion, visual and hearing loss, motor defects, epilepsy, cerebral palsy and death in newborn infants. The severity of apoptosis following hypoxiaischemia and recanalization is an indicator of brain damage. In this study, we investigated the effect of hydroxychloroquine molecule, an antimalarial drug, on apopitotic processes and whether it improves neurocognitive functions in the long term by applying behavioral experiments in a neonatal rat model of HIBI. Seven-day-old newborn rats were randomly divided into four groups. In total, 33 rats were used in the study. HCQ group (n= 8), HCQ-HT group (n= 8) and HIE group (n= 9) were left hypoxic for 2.5 hours by inhalation of 8% oxygen and 92% nitrogen mixture after left arterial carotid communis ligation. In the SHAM group (n=8), the incision was performed without carotid artery ligation. Hydroxychloroquine (80 mg/kg, intraperitoneal) was administered every 24 hours for 3 days in HCQ-HT and HCQ groups; physiologic saline (10 cc/kg, intraperitoneal) was administered every 24 hours for 3 days in HIE and SHAM groups. HCQ-HT group also had hypothermia for 4 hours. Open field experiment was used to investigate anxiety-like behaviors and locomotor competencies, and Morris water tank test was used to investigate the effects on learning and memory in the late period. After the behavioral tests, all rats were decapitated under isoflurane anesthesia. While the initial weights of the rats were similar, the SHAM, HCQ-HT, HCQ and HIE groups had the best weight after 6 weeks (p<0.05). No infarct was observed in HCQ-HT and HCQ groups, while infarct area was obvious in HIE group. The number of apopitotic cells stained with TUNEL was lower in HCQ-HT and HCQ groups (p<0.001). While anxiety-like behavior was not different in the open field test (p=0.10), spatial learning and memory ability were better in HCQ-HT and HCQ groups (p=0.01, p<0.001). In conclusion, we showed that intraperitoneal HCQ treatment and hypothermia in rats with HIBI decreased the severity of HIBI, contributed to weight gain and reduced malnutrition. HCQ significantly decreased infarct volume and severity of neuronal damage. Both HCQ and HCQ with hypothermia treatment had a positive effect on the spatial learning and memory abilities of rats. However, further studies are needed for the use and side effects of HCQ in HIBH. Key Words: hypoxic ischemic brain injury, rat, brain, hydroxychloroquine, behavior