Reducing the 'Toll' of Nerve Pain - TLR4

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Reducing the 'Toll' of Nerve Pain

06 Apr 2005 Medical News Today

According to a newly published study, the Toll-like receptor 4 (TLR4)

plays a critical role in inducing neuropathic pain--a debilitating

condition in which nerves generate pain by themselves, without a

painful stimulus.

TLR4 is expressed exclusively by microglia, immune cells of the

central nervous system (CNS) that become activated soon after an

injury. Following nerve injury in animals, TLR4 has been implicated

in behavioral hypersensitivity--a model of neuropathic pain whereby

the CNS overreacts to sensory input.

To determine if TLR4 contributes to neuropathic pain, Flobert Tanga

and colleagues severed a nerve in the lower back of mice lacking

functional TLR4. To assess hypersensitivity, the researchers observed

how the mice reacted when their hindpaws were touched or exposed to

heat. TLR4-deficient mice were less sensitive than normal mice and

exhibited decreased expression of activated microglia.

These results demonstrate that TLR4 contributes to the initiation of

the CNS immune response, leading to behavioral hypersensitivity.

Further understanding of TLR4's ability to activate hypersensitivity

may provide an opportunity to regulate microglial activation and

alleviate chronic pain due to nerve damage.

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