Favorable effects of MMP-9 knockdown in murine herpes simplex encephalitis using small interfering RNA.
OBJECTIVE
The prognosis of herpes simplex encephalitis (HSE) remains poor despite available antiviral treatment. Matrix metalloproteinase-9 (MMP-9) is currently considered to play a major role in promoting cerebrovascular complications which contribute to the high  mortality and morbidity of HSE. We hypothesize that temporally knockdown MMP-9 expression in early phase of HSE might be an effective treatment strategy.


METHODS
The animal models of herpes simplex encephalitis were established by intracerebrally inoculated herpes simplex virus  type 1 (HSV-1) in mice. Mice were inoculated intracerebrally with MMP-9 targeting siRNA (MMP-9 siRNA). MMP-9 expression was assessed by RT-PCR and western blot analysis at 3 and 7 days after HSV-1 infected. The blood-brain barrier (BBB) permeability was quantitated by Evans blue dye  extravasations and brain water content. Immunohistochemistry method was adopted to analyse the expression of AQP4 protein. Quantitative real-time PCR analysis was used to detect cytokines expression. Neurological score was quantified using an established neurological scale at 7 days after  HSE.


RESULTS
Using synthetic small interfering RNA, we found a single intracerebral injection of siRNA targeting murine MMP-9 mRNA (MMP-9 siRNA) silenced MMP-9 expression and reduced it to normal level at day 7 post-infection. The improvement in neurological function and increased  cumulative survival reflected the functional consequence of this therapy. MMP-9 knockdown mice also displayed less uptake of Evans blue and reduced brain water content compared with control siRNA-treated group. Also the HSV-1-induced upregulation of proinflammatory cytokines was significantly  diminished in MMP-9 siRNA-treated mice. In addition, aquaporin-4 expression in perivascular decreased in MMP-9 siRNA-treated mice and might contribute to the protection of blood-brain barrier.


CONCLUSIONS
This compelling evidence suggests that MMP-9 is a key pathogenic factor  within HSE, and local injection of synthetic siRNA in the brain could knock down MMP-9 expression in acute phase of HSE, reduce brain edema and improves mice neurological function and increase cumulative survival.
Zhou
Yu
Y
Department of Neurology, Renmin Hospital of Wuhan University, China. zhouyu131@gmail.com
Lu
Zu-Neng
ZN
Guo
Yuan-Jin
YJ
Mei
Yuan-Wu
YW
D000818:Animals; D020803:Encephalitis, Herpes Simplex / Q000201:enzymology* / Q000235:genetics* / Q000628:therapy; D005260:Female; D055785:Gene Knockdown Techniques / Q000379:methods; D015316:Genetic Therapy / Q000379:methods*; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D034741:RNA, Small Interfering / Q000235:genetics*; D016896:Treatment Outcome
D034741:RNA, Small Interfering; D020780:Matrix Metalloproteinase 9