Effects of garlic extract (Allium sativum) on neutrophil migration at the cellular level

Studies of the effects of garlic extract on oxidative and lipoprotein levels have yielded widely different findings. Leukocytes play an important role during many processes, including inflammation. They migrate from intravascular spaces into tissues and attack microorganisms. In a recent study, the inhibitory effects of the nonsteroidal antiinflammatory drug, ibuprofen, on leukocyte transmigration were demonstrated using an in vitro assay. Little is known about the cellular effects of garlic extracts (Allium sativum). The aim of the current study was to investigate the influence of garlic extract on leukocyte migration through endothelial cell monolayers and thereby evaluate a possible role in inflammatory processes. Human umbilical endothelial cells were cultured on microporous membranes to make an endothelial cell monolayer (ECM). Freshly isolated neutrophils were used in a recently described migration assay. The amount of untreated neutrophils migrating through the untreated ECM was used as control and set at 100%. Neutrophils and/or ECM were pretreated with garlic extract using moderate, higher, and lower concentrations. Moderate plasma concentrations of garlic extract inhibited neutrophil migration through ECM significantly (64 +/- 5.8% standard deviation [SD]; P < 0.05) when both cell types were treated, (a situation that may have clinical relevance). Treating either neutrophils or ECM alone showed significant reductions in migratory rate (neutrophils treated alone: 81 +/- 7.7% SD, P < 0.05; ECM alone: 70 +/- 6.7%, P < 0.05). Thus, garlic extract is identified as a potent inhibitor of leukocyte migration through endothelial cell monolayers. Treatment of both cell types has an additive effect. Endothelial cells seem to be more affected than neutrophils. Further investigations are necessary to understand the potential clinical consequences.