Neuronal cell death in alphavirus encephalomyelitis

Area of Science:

• Neuroscience
• Virology
• Immunology

Background:

• Alphaviruses, such as Sindbis virus (SINV), are mosquito-borne RNA viruses causing diverse human diseases, including neurological conditions.
• SINV serves as a model for alphavirus-induced neurological disease, primarily targeting central nervous system (CNS) neurons.
• Susceptibility to fatal SINV disease is higher in young animals, linked to apoptosis induction in immature neurons.

Purpose of the Study:

• To investigate the mechanisms of SINV-induced neuronal cell death in the CNS.
• To identify host and viral factors influencing neuronal fate during SINV infection.
• To explore therapeutic strategies for preventing SINV-induced neurological damage.

Main Methods:

• In vitro studies using neuroblastoma cells to examine viral fusion-induced apoptosis.
• Analysis of apoptotic pathways, including acid sphingomyelinase, ceramide, poly(ADP-ribose) polymerase, cytochrome c, and caspases.
• In vivo studies in young and old mice to compare disease outcomes and neuronal death mechanisms (apoptosis vs. necrosis).
• Evaluation of preventative treatments, including antioxidants, caspase inhibitors, Bcl-2, Beclin-1, protease inhibitors, and glutamate receptor antagonists.

Main Results:

• SINV-induced apoptosis in immature neurons involves viral envelope fusion with endosomal membranes, activating acid sphingomyelinase and ceramide production.
• The apoptotic cascade includes poly(ADP-ribose) polymerase activation, cytochrome c release, and effector caspase activation.
• Young animals exhibit higher susceptibility due to SINV-induced apoptosis in immature neurons, while older animals may experience necrosis in motor neurons or mixed death in hippocampal neurons.
• Neuronal death in surrounding uninfected neurons was also observed and could be mitigated.

Conclusions:

• SINV triggers neuronal apoptosis through a specific molecular pathway initiated by viral fusion and ceramide generation.
• Therapeutic interventions targeting apoptotic pathways (antioxidants, caspase inhibitors) or excitotoxicity (glutamate antagonists) can prevent or delay SINV-induced neuronal death.
• Understanding these mechanisms is crucial for developing treatments against alphavirus-induced neurological diseases.