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Published on: December 26, 2015
Favorable effects of MMP-9 knockdown in murine herpes simplex encephalitis using small interfering RNA
Yu Zhou1, Zu-Neng Lu, Yuan-Jin Guo
1Department of Neurology, Renmin Hospital of Wuhan University, China. zhouyu131@gmail.com
Background And Purpose:
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.
Discussion:
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.
Insights
Targeting matrix metalloproteinase-9 (MMP-9) with siRNA in herpes simplex encephalitis (HSE) reduced brain swelling and improved survival in mice. This approach offers a potential new treatment strategy for HSE by silencing MMP-9 expression early in the infection.
Area of Science:
- Neuroscience
- Virology
- Molecular Biology
Background:
- Herpes simplex encephalitis (HSE) has a poor prognosis despite antiviral treatments.
- Matrix metalloproteinase-9 (MMP-9) exacerbates HSE by promoting cerebrovascular complications.
- High mortality and morbidity rates underscore the need for novel HSE therapeutic strategies.
Purpose of the Study:
- To investigate the therapeutic potential of targeting MMP-9 in the early stages of HSE.
- To hypothesize that temporally knocking down MMP-9 expression can be an effective treatment for HSE.
Main Methods:
- Established mouse models of HSE via intracerebral herpes simplex virus type 1 (HSV-1) inoculation.
- Administered MMP-9 targeting siRNA (MMP-9 siRNA) via intracerebral injection.
- Assessed MMP-9 expression, blood-brain barrier (BBB) permeability, aquaporin-4 (AQP4) expression, cytokine levels, and neurological function.
Main Results:
- Single intracerebral injection of MMP-9 siRNA effectively silenced MMP-9 expression by day 7 post-infection.
- Mice treated with MMP-9 siRNA showed improved neurological function and increased cumulative survival.
- MMP-9 knockdown reduced BBB permeability, brain edema, and suppressed HSV-1-induced pro-inflammatory cytokine upregulation.
Conclusions:
- MMP-9 is a critical pathogenic factor in HSE.
- Local siRNA injection in the brain can effectively reduce MMP-9 expression during the acute phase of HSE.
- This strategy improves neurological outcomes and survival rates in HSE models, suggesting therapeutic potential.
