Since NO is synthesized from L-arginine by inducible NO
synthase (iNOS) expression, the effect on iNOS expression at
the transcriptional level was investigated by real time RTPCR.
Similar to the effect on nitrite production, a statistically
significant inhibition of iNOS mRNA levels by luteolin and L7OG
was observed (Fig. 4a), the effect being less prominent with
L7OG than with luteolin aglycone. No inhibition was observed
after cell treatment with isoorientin, cassiaoccidentalin
B or orientin. These results indicate the correlation between
the effects on NO production and iNOS expression, and demonstrate
the anti-inflammatory potential of luteolin aglycone
and L7OG, although the latter is at a lower extent.
Next, the effect of luteolin and luteolin glycosides on the
expression of some cytokines, namely TNF-α, IL-1β and IL-6,
was evaluated by real time RT-PCR. Luteolin aglycone significantly
inhibited LPS-induced expression of these three cytokines
(Fig. 4b–d). TNF-α and IL-6 expression was reduced by
53.3 ± 10.0% and 73.7 ± 34.7%, respectively, and IL-1β expression
was completely abolished. Concerning the effect of luteolin
glycosylated, only L7OG modulated cytokine expression, reducing
the LPS-induced IL-1β expression by 45.7 ± 30.4%, thus
reinforcing the L7OG anti-inflammatory properties, by
inhibiting NO and also IL-1β production. Interestingly, the
inhibition of NO production and iNOS expression by luteolin
5-O-glucoside was recently reported (Jung, Jin, Min, Kim, & Choi,
2012), thus indicating that the position of O-glycosylation in
the A ring did not affect the anti-inflammatory activity.
All together, the results demonstrated that glycosylation decreased
luteolin activity in vitro and the decrease was higher
for the C-glycosylation than O-glycosylation in the A ring.
Accordingly, previous data evidenced that glycosylation of
Since NO is synthesized from L-arginine by inducible NOsynthase (iNOS) expression, the effect on iNOS expression atthe transcriptional level was investigated by real time RTPCR.Similar to the effect on nitrite production, a statisticallysignificant inhibition of iNOS mRNA levels by luteolin and L7OGwas observed (Fig. 4a), the effect being less prominent withL7OG than with luteolin aglycone. No inhibition was observedafter cell treatment with isoorientin, cassiaoccidentalinB or orientin. These results indicate the correlation betweenthe effects on NO production and iNOS expression, and demonstratethe anti-inflammatory potential of luteolin aglyconeand L7OG, although the latter is at a lower extent.Next, the effect of luteolin and luteolin glycosides on theexpression of some cytokines, namely TNF-α, IL-1β and IL-6,was evaluated by real time RT-PCR. Luteolin aglycone significantlyinhibited LPS-induced expression of these three cytokines(Fig. 4b–d). TNF-α and IL-6 expression was reduced by53.3 ± 10.0% and 73.7 ± 34.7%, respectively, and IL-1β expressionwas completely abolished. Concerning the effect of luteolinglycosylated, only L7OG modulated cytokine expression, reducingthe LPS-induced IL-1β expression by 45.7 ± 30.4%, thusreinforcing the L7OG anti-inflammatory properties, byinhibiting NO and also IL-1β production. Interestingly, theinhibition of NO production and iNOS expression by luteolin5-O-glucoside was recently reported (Jung, Jin, Min, Kim, & Choi,2012), thus indicating that the position of O-glycosylation inthe A ring did not affect the anti-inflammatory activity.All together, the results demonstrated that glycosylation decreasedluteolin activity in vitro and the decrease was higherfor the C-glycosylation than O-glycosylation in the A ring.Accordingly, previous data evidenced that glycosylation of
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