Studies on biological effects of plant lectins on animal cells andtissues
Monira PERVIN
Department of Food and Nutritional Sciences Graduate School of Nutritional andEnvironmental Sciences
Plant lectins have various biological effects on animal functions such as cell
agglutination, mitosis, toxicity, cell growth inhibition, and anti-cancer andimmunomodulatory effects. The involvement of lectins in our health and their relationshipto degenerative disease is still an emerging science. The present study aimed to provide
precise data for demonstrating the biological effects of plant lectin on animal cells andtissues.
To examine whether plant lectin could affect the gene expression of cytokines,
gluconeogenic enzyme and transcription factor genes in mouse tissues and cultured cells,mRNA expression levels were measured by reverse transcription-polymerase chain reaction(RT-PCR) and quantitative real-time PCR (Q-PCR). The results indicated that Japanese mistletoe

lectins (ML-J) increased the gene expression of proinflammatory cytokines interleukin(IL)-8, tumor necrosis factor-α (TNF-α) and IL-6 in Caco-2 cells at 10 ng/mL and TNF-α
and IL-6 in the mouse duodenum at 10 μg/head. It was also found that ML-J caused
increased (IL-8) cytokine production in Caco-2 cells with dose-dependently. To confirm
the direct action of ML-J on Caco-2 cells through its carbohydrate-binding activity, aninhibition test was performed by lactose (200 mM), and the results showed that ML-J’saction was carbohydrate-dependent. Intragastrically administered Lens culinaris agglutinin(LCA) at different concentration (20, 100 and 200 μg/head) and tomato lectin (TL) at 2mg/head caused significantly down-regulation of Th1 cytokines IFN-γ andpro-inflammatory cytokines TNF-α, IL-2, IL-12b and IL-1β in mouse intestine. The results
suggest that LCA and TL have direct effects on modulation of the gene expression ofTh1/Th2 balance to promote allergic activity and anti-inflammatory activity in vivo. The
effects of LCA and TL on the gene expression of gluconeogenic enzymes in mouse tissues
and Caco-2 cells, results indicated that LCA caused an up-regulation of the gene expressionof the gluconeogenic enzymes glucose-6-phosphatase (G6Pase) and phosphoenolpyruvatecarboxykinase (PEPCK) in mouse duodenum and in Caco-2 cells, whereas insulin had theopposite effect. The results also showed that LCA caused an increase in the intestinal gene
expression of either hepatocyte nuclear factor (HNF)1α or HNF4α. TL caused an
up-regulation of the gene expression of G6Pase and PEPCK in the mouse duodenum. Theeffects of methyl α-D-mannoside (MAM) on the change in gene expression in Caco-cellcaused by LCA was examined, results indicated that up-regulated gene expression ofG6Pase induced by LCA was attenuated by MAM. The up-regulation of PEPCK
expression by LCA tended to be reduced in the presence of MAM. These findings suggestthat LCA may have unfavorable effects. Therefore, lentil beans should be cooked well toremove bioactivity of LCA. This study provides the first example to show that a perorally
administered plant lectin affects gene expression in the duodenum.
The present study provided some new information concerning the physiologicaleffects of plant lectin on animal cells and tissues and suggested both of beneficial anddeleterious effects. Elucidations of further biological effects of plant lectins will help todevelop new strategies for maintain our health.