Inhibition of PDE10A-Rescued TBI-Induced Neuroinflammation and Apoptosis through the cAMP/PKA/NLRP3 Pathway

Abstract

Phosphodiesterase 10A (PDE10A) is a dual-substrate phosphodiesterase that is highly expressed in the striatal complex. PDE10A is an important target for the treatment of ganglion dysfunction and neuroinflammation-related diseases, but its possible impact on traumatic brain injury (TBI) is still unclear. This study aims to investigate the protective effects of inhibiting PDE10A on neuroinflammation post-TBI injury and its possible molecular mechanism. The expression of PDE10A in rats and HT22 cells was determined by Western blotting. The neurological dysfunction of these rats was detected by Nissl staining, hematoxylin-eosin (HE) staining, and Morris water maze test. The activity of HT22 cells was measured by MTT. The findings of this study suggest that PDE10A is highly expressed in the brain tissue of TBI rats and HT22 cells induced by mechanical injury. Inhibition of PDE10A reduces the expression of interleukin-1β (IL-1β) and interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) in HT22 cells induced by mechanical injury to inhibit cell apoptosis. Simultaneously, inhibition of PDE10A in TBI rats reduces the time to find a visible platform in the same pool, while cAMP/PKA activator treatment alleviates all of the abovementioned phenomena. Additionally, it is further confirmed that inhibition of PDE10A activates the cAMP/PKA pathway and downregulates the expression of NRLP3. These findings demonstrate that inhibition of PDE10A exerts neuroprotection by inhibiting apoptosis and inflammation following TBI, at least partially by the cAMP/PKA/NLRP3 pathway.

Figure 1

PDE10A is highly expressed in TBI tissues and HT22 cell lines. The expression of PDE10A in tissues and HT22 cells were measured by Western blotting (a, b). ^∗∗Significant compared to sham/control (^∗∗P < 0.01).

Figure 2

PDE10A promotes neurological dysfunction in TBI rats. Representative images of the escape track of rats in the Morris water maze test (a). The hematoxylin and eosin (H&E)-stained and Nissl-stained hippocampal sections (×100) (b) and (c). ^∗∗Significant compared to sham/control (^∗∗P < 0.01).

Figure 3

PDE10A promotes neuroinflammation of HT22 cells post mechanical injury. The expression of TNF-α, IL-1β, IL-6, Bax, Bcl-2, and caspase-3 in HT22 cells were measured by Western blotting (a) and (c). HT22 cells viability was measured by the MTT assay (b). ^∗∗Significant compared to control (^∗∗P < 0.01). ^##Significant compared to PDE10A inhibitor treatment (^##P < 0.01).

Figure 4

PDE10A inhibiting the cAMP/PKA pathway. The expression of cAMP p-PKA and PKA in HT22 cells were measured by Western blotting. HT22 ^∗∗significant compared to control (^∗∗P < 0.01). ^##Significant compared to MI (^##P < 0.01).

Figure 5

cAMP/PKA inhibits NLPR3 expression. The expression of p-PKA, PKA, and NLRP3 in HT22 cells were measured by Western blotting. HT22 ^∗∗significant compared to control (^∗∗P < 0.01). ^##Significant compared to MI (^##P < 0.01). ^ΔΔ was considered significant compared to cAMP/PKA activator treatment (^ΔΔP < 0.01). ^@@Significant compared to MI + cAMP/PKA activator treatment (^@@P < 0.01).

Figure 6

cAMP/PKA alleviated TBI damage by inhibiting NLPR3. The expression of NLPR3, caspase1, TNF-α, IL-1β, IL-6, Bax, Bcl-2, and caspase-3 in HT22 cells was measured by Western blotting (a–c) and (f). HT22 cells viability was measured by the MTT assay (d). Representative images of the escape track of rats in the Morris water maze test (e). ^∗∗Significant compared to control (^∗∗P < 0.01). ^##Significant compared to MI/TBI (^##P < 0.01). ^ΔΔSignificant compared to cAMP/PKA activator treatment (^ΔΔP < 0.01).