From the article:

The researchers treated rats with alcohol, tobacco smoke or both twice a day for 28 days and then compared their brains with control animals that didn’t receive either substance. They found that the combined alcohol and smoking treatment increased the level of reactive oxygen species in the hippocampus compared with control animals or rats given tobacco smoke alone. In all of the brain areas studied, combined alcohol and smoking increased the levels of specific pro-inflammatory cytokines more than either treatment alone.

Reduced levels of BDNF, another harbinger of bad news:

And in the striatum and frontal cortex, rats with both treatments showed lower levels of brain-derived neurotrophic factor, a growth factor that helps existing neurons survive and stimulates the growth of new ones. These results suggest that alcoholics who smoke could be at additional risk for neural damage, the researchers say.