Heat shock protein (HSP)60 is primarily a
mitochondrial protein. Previous experiments have found that changes in the location of intracellular HSP60 have been associated with apoptosis. Extracellular HSP60 mediates apoptosis via its
ligand, Toll‑like receptor (TLR)-4. TLR-4 is an important factor expressed on microglia, with a central role in generating neuroimmune responses in the pathogenesis of
neurodegenerative disorders.
Naloxone is a highly effective nonselective
opioid receptor antagonist, and has been reported to be pharmacologically beneficial for the treatment of
brain diseases through inhibiting microglia activation. However, the mechanisms underlying these beneficial effects of
naloxone remain poorly understood. The present study aimed to investigate the role of HSP60 in the
neuroprotective effects of
naloxone on the production of proinflammatory mediators in
lipopolysaccharide (LPS)-stimulated BV2 murine microglial cells and the possible signaling pathways involved. The results demonstrated that
naloxone significantly inhibited the expression and release of HSP60 in BV2 cells. The expression levels of heat shock factor (HSF)-1 were upregulated in LPS‑activated BV2 cells, which indicated that the increased expression of HSP60 was driven by HSF-1 activation. However, increased HSF‑1 levels may be downregulated by
naloxone. The levels of TLR‑4 were elevated in activated BV2 cells, and then inhibited by
naloxone. Activation of TLR‑4 is characterized by activation of nuclear factor-κB (NF-κB) followed by the production of various proinflammatory and neurotoxic factors. Data from the present study demonstrated that
naloxone reduced the expression levels of NF-κB and its upstream
protein caspase‑3, and reduced the LPS-induced production of
nitric oxide,
inducible nitric oxide synthase,
tumor necrosis factor α, interleukin-1β and
interleukin-6 in BV2 microglia. In light of this data, it was concluded that
naloxone may exert its neuroprotective and anti‑inflammatory effects by inhibiting microglia activation through a HSP60‑TLR‑4‑NF‑κB signaling pathway.