Nitric oxide synthase mediates cerebellar dysfunction in mice exposed to repetitive blast-induced mild traumatic brain injury

Aric F Logsdon,Murray A Raskind,Abigail G Schindler,David G Cook,James S Meabon,Elaine R Peskind,William A Banks,C Dirk Keene,Mayumi Yagi,Desiree A Marshall,Daniel P Perl,Melanie J Herbert

doi:10.1038/s41598-020-66113-7

Abstract

We investigated the role of nitric oxide synthase (NOS) in mediating blood-brain barrier (BBB) disruption and peripheral immune cell infiltration in the cerebellum following blast exposure. Repetitive, but not single blast exposure, induced delayed-onset BBB disruption (72 hours post-blast) in cerebellum. The NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) administered after blast blocked BBB disruption and prevented CD4+ T-cell infiltration into cerebellum. L-NAME also blocked blast-induced increases in intercellular adhesion molecule-1 (ICAM-1), a molecule that plays a critical role in regulating blood-to-brain immune cell trafficking. Blocking NOS-mediated BBB dysfunction during this acute/subacute post-blast interval (24–71 hours after the last blast) also prevented sensorimotor impairment on a rotarod task 30 days later, long after L-NAME cleared the body. In postmortem brains from Veterans/military Servicemembers with blast-related TBI, we found marked Purkinje cell dendritic arbor structural abnormalities, which were comparable to neuropathologic findings in the blast-exposed mice. Taken collectively, these results indicate that blast provokes delayed-onset of NOS-dependent pathogenic cascades that can later emerge as behavioral dysfunction. These results also further implicate the cerebellum as a brain region vulnerable to blast-induced mTBI.

Highlights

We investigated the role of nitric oxide synthase (NOS) in mediating blood-brain barrier (BBB) disruption and peripheral immune cell infiltration in the cerebellum following blast exposure
We have previously shown that this same 3X exposure regimen caused acute BBB disruption, which was closely associated with later emerging chronic neuron loss in the cerebellum[11]
Monocyte (CD11b+, CD45 high) infiltration, which was not significantly affected by blast exposure in either the cerebellum (F(2,24) = 0.081, n.s.) or forebrain (F(2,24) = 0.902, n.s.). These results demonstrate that repetitive blast exposure induces brain region-specific, NOS-dependent, CD4+ T-cell infiltration that corresponds to the differential effects of blast on BBB integrity in the cerebellum versus forebrain regions

Summary

Introduction

We investigated the role of nitric oxide synthase (NOS) in mediating blood-brain barrier (BBB) disruption and peripheral immune cell infiltration in the cerebellum following blast exposure. In postmortem brains from Veterans/military Servicemembers with blast-related TBI, we found marked Purkinje cell dendritic arbor structural abnormalities, which were comparable to neuropathologic findings in the blast-exposed mice Taken collectively, these results indicate that blast provokes delayed-onset of NOS-dependent pathogenic cascades that can later emerge as behavioral dysfunction. We and others have shown that blast exposure causes transient BBB disruption[8,10,26], suggesting that blast stimulates short-term neurovascular repair processes that interact with more protracted, co-occurring, pathological cascades that undermine BBB integrity In this regard, blast has been shown to provoke delayed-onset BBB disruption, days after an initial BBB opening was restored to normal[8].

Methods

Results

Conclusion