Suppression by delta-9-tetrahydrocannabinol of lipopolysaccharide-induced and intrinsic tyrosine phosphorylation and protein expression in mouse peritoneal macrophages.

Lipopolysaccharide (LPS, 100 ng/mL)-induced tyrosine phosphorylation of four proteins (p41, p42, p77, and p82) in mouse resident peritoneal macrophages was observed using a monoclonal anti-phosphotyrosine antibody PY20 immunoblotting method. Macrophages pretreated for 3 hr with 1 microgram delta-9-tetrahydrocannabinol (THC)/mL had decreased tyrosine phosphorylation of p77 and p82 after incubation with LPS for 30 min. Simultaneous treatment of macrophages with THC (10 micrograms/mL) plus LPS for 30 min had a similar effect on p77 and p82 tyrosine phosphorylation. When the THC pretreatment protocol was combined with the simultaneous treatment protocol, 0.5 and 5 micrograms THC/mL, respectively, completely blocked LPS-induced p77 and p82 tyrosine phosphorylation. However, neither simultaneous treatment with THC nor pre- and simultaneous treatment had any effect on LPS-induced tyrosine phosphorylation of p41 and p42 in macrophages. Pretreatment with 1 microgram THC/mL followed by simultaneous treatment with 10 micrograms THC/mL induced a p43 protein that showed tyrosine phosphorylation in place of p41 and p42. Further analysis of THC effects on macrophages revealed an increase in tyrosine phosphorylation as an immediate early even after THC treatment. Prolonged treatment of macrophages with THC resulted in a broad suppression of tyrosine phosphorylation and some cellular protein expression. Three cellular proteins (p65, p70, and p72) seemed most susceptible to inhibition by THC. The data suggest that suppression of tyrosine phosphorylation by THC in macrophages may be one of the mechanisms associated with inhibition of cell function, including the suppression of tumor necrosis factor-alpha release from macrophages.