TLR4 and asthma: The NF-κB signaling pathway, the most important downstream inflammatory signaling pathway of cAMP, could further inhibit the release of proinflammatory factors by decreasing the activity of TLR4 and reducing the activity of NF-κB and Th2 factors, such as TNF-α, IL-6, IL-4, and IL-5 in asthmatic mice [48], thus alleviating asthma.