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. 2012 Feb 22;7(2):e31951. doi: 10.1371/journal.pone.0031951

Figure 6. Stimulation of the H2 receptor increased cAMP and PKA activity was required for TNF suppression.

Figure 6

Signaling pathway studies were performed to determine the effect of histamine on cAMP production and the role of PKA activity in TNF suppression. A. Treatment of activated THP-1 cells with L. reuteri 6475 CM or histamine increased intracellular cAMP. The increase in cAMP was blocked by a specific H2 receptor antagonist, ranitidine. Results represent the mean ± SD (n = 2), *p value<0.05 compared to medium control, **p value<0.05 compared to L. reuteri 6475, #p value<0.05 compared to histamine. B. Inhibition of PKA activity partially blocked TNF suppression by TNF-inhibitory compounds L. reuteri 6475 CM, HILIC-HPLC fraction B3, histamine, and dcAMP. Results represent the mean ± SD (n = 9), *p value<0.05 compared to H89 treated samples.