Neuroprotective and antimalarial effects of Juglans regia leaf extracts in a murine model of cerebral malaria

Afra Alharbi Shurug Albasyouni Esam Al-shaebi Saleh Al Quraishy Rewaida Abdel-Gaber ^*

• King Saud University, Riyadh, Saudi Arabia

Background: Malaria is a major public health problem caused by the apicomplexan Plasmodium parasite. Cerebral malaria (CM) is the most critical outcome of Plasmodium infection. It is becoming more difficult to manage, particularly in areas of multi-drug resistance. Scientists are focused on identifying alternative strategies to combat malaria infection. Therefore, this study was designed to evaluate the activity of Juglans regia leaf extract (JRLE) in Plasmodium berghei-infected C57BL/6 mice Methods: The J. regia leaf extract (JRLE) was prepared using methanol and characterized by Fourier-transform infrared spectroscopy (FT-IR). Female C57BL/6 mice were divided into six groups (5 mice/group): control, non-infected but JRLE-treated (500 mg/kg), P. berghei-infected non-treated, and P. berghei-infected treated with JRLE (250 or 500 mg/kg) or chloroquine (10 mg/kg). Groups (3–6) were infected intraperitoneally with P. berghei (1 × 10⁵). Treatment (oral JRLE or chloroquine) was administered for five days starting on day 4. Parasitemia, survival, and body weight were assessed, and brains were collected on day 9 p.i. for histopathological analysis (H&E staining) and GFAP immunohistochemistry. GABA, glutamate, neurotransmitters (epinephrine, norepinephrine, dopamine, serotonin), and mRNA expression of signaling genes (Chrnb2, Gabbr1, Gnai1, Gria2) were evaluated using ELISA and real-time PCR. Results: Phytochemical screening by FT-IR demonstrated the presence of 10 functional groups in the JRLE. By day 9 after infection with the P. berghei parasite, the parasitemia was significantly reduced after JRLE treatment with a dose of 500 mg/kg (6.33 ± 1.18%) compared to the infected group (23.84 ± 2.06%) with a positive correlation with body weight. Our data showed that JRLE prolonged the survival curve of the infected mice. JRLE ameliorates the reduction of the brain index caused by P. berghei infection. Furthermore, histological analysis showed that infection with P. berghei exacerbates brain damage as evidenced by degeneration of Purkinje cells, cerebral hemorrhage, intravascular sequestrations of parasitized red blood corpuscles (pRBCs), and infiltration of lymphocytes. At the same time, treatment with JRLE mitigates the brain injury induced by the infection. JRLE reduced the level of GFAP expression in the brain tissue of the infected mice. Additionally, treatment with JRLE ameliorates brain neurotransmitter disbalance (i.e. epinephrine, norepinephrine, dopamine,