Nicotine (0.3 and 1 mM) significantly reduced human β-defensin-2 mRNA and protein expression and significantly increased IL-8 production, compared with cultures with no nicotine treatment, in response to P. gingivalis LPS and TNF-α-induced human gingival epithelial cells from subjects with clinically healthy periodontium and no history of periodontitis (91). Here, TNF is linked to periodontitis.