L-arginine supplementation and thromboxane synthase inhibition increases cerebral blood flow in experimental cerebral malaria

Aline S Moreira,Leonardo J M Carvalho,Cláudio Tadeu Daniel-Ribeiro,Guilherme S Sanches,David C Malvar,Vanessa Estato,Eduardo Tibirica,Fabiana Gomes

doi:10.1038/s41598-019-49855-x

Abstract

Cerebral malaria pathogenesis involves vascular dysfunction with low nitric oxide (NO) bioavailability, vasoconstriction and impaired vasodilation, leading to ischemia, tissue hypoxia and ultimately death. Cerebral blood flow (CBF) involves NO and other pathways, including arachidonic acid (AA)-derived metabolites. Here we show that mice with experimental cerebral malaria (ECM) by P. berghei ANKA showed marked decreases in CBF (as assessed by laser speckle contrast imaging - LSCI) and that administration of L-arginine supplementation (50 mg/kg) and/or of the thromboxane synthase inhibitor Ozagrel (100 mg/kg) induced immediate increases in CBF. L-arginine in combination with artesunate (32 mg/kg) induced immediate reversal of brain ischemia in the short-term (1 hour), but the effect subsided after 3 and 6 hours. Neither L-arginine nor Ozagrel reversed blood brain barrier breakdown. Mice with ECM showed brain levels of selected AA-derived metabolites with a vasoconstrictor profile, with increased levels of 8-isoprostanes, 20-HETE and 14,15-DHET, whereas mice infected with a non-ECM-inducing strain of P. berghei (NK65) showed a vasodilator profile, with normal levels of 20-HETE and 14,15-DHET and increased levels of PGE2. L-arginine is capable of partially reversing cerebral ischemia and AA metabolites may play a role in the cerebrovascular dysfunction in ECM.

Highlights

Cerebral malaria, a deadly neurological complication of Plasmodium falciparum infection, shows features of a severe vasculopathy, which results in impaired perfusion, ischemia and hypoxia[1,2,3,4]
In the present study we investigated two different and interrelated approaches to reverse cerebral ischemia in mice with late-stage experimental cerebral malaria (ECM), asking: (a) whether the described effect of L-arginine in dilating cerebral vessels or preventing the aggravation of vasoconstriction results in substantial increases in cerebral blood flow (CBF); (b) whether the pharmacological inhibition of the synthesis of the potent arachidonic acid (AA)-derived vasoconstrictor thromboxane A2, alone or in combination with L-arginine supplementation, results in increased CBF in ECM, as a first effort to address the role of AA metabolites in ECM cerebrovascular dysfunction
Cerebral malaria is a severe vasculopathy characterized by phenomena such as blockade of the cerebral microcirculation by pRBCs and leukocytes, inflammation, endothelial activation and dysfunction, ischemia/hypoxia and breakdown of the blood-brain barrier with resulting edema

Summary

Introduction

A deadly neurological complication of Plasmodium falciparum infection, shows features of a severe vasculopathy, which results in impaired perfusion, ischemia and hypoxia[1,2,3,4]. In the present study we investigated two different and interrelated approaches to reverse cerebral ischemia in mice with late-stage ECM, asking: (a) whether the described effect of L-arginine in dilating cerebral vessels or preventing the aggravation of vasoconstriction results in substantial increases in cerebral blood flow (CBF); (b) whether the pharmacological inhibition of the synthesis of the potent AA-derived vasoconstrictor thromboxane A2, alone or in combination with L-arginine supplementation, results in increased CBF in ECM, as a first effort to address the role of AA metabolites in ECM cerebrovascular dysfunction. We determined the levels of relevant AA metabolites (8-isoprostanes, TxA2, 20-HETE, PGE2, and 14,15-dihydroxy-5Z,8Z,11Z-e icosatrienoic acid [14,15-DHET]) in the brain of mice with ECM or infected with a P. berghei strain (NK65) that does not cause ECM

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Results

Conclusion