Conditional knockout of ASK1 in microglia/macrophages attenuates epileptic seizures and long-term neurobehavioural comorbidities by modulating the inflammatory responses of microglia/macrophages

Background Apoptosis signal-regulating kinase 1 (ASK1) not only causes neuronal programmed cell death via the mitochondrial pathway but also is an essential component of the signalling cascade during microglial activation. We hypothesize that ASK1 selective deletion modulates inflammatory responses in microglia/macrophages(Mi/M phi) and attenuates seizure severity and long-term cognitive impairments in an epileptic mouse model. Methods Mi/M phi-specific ASK1 conditional knockout (ASK1 cKO) mice were obtained for experiments by mating ASK1(flox/flox) mice with CX3CR1(creER) mice with tamoxifen induction. Epileptic seizures were induced by intrahippocampal injection of kainic acid (KA). ASK1 expression and distribution were detected by western blotting and immunofluorescence staining. Seizures were monitored for 24 h per day with video recordings. Cognition, social and stress related activities were assessed with the Y maze test and the three-chamber social novelty preference test. The heterogeneous Mi/M phi status and inflammatory profiles were assessed with immunofluorescence staining and real-time polymerase chain reaction (q-PCR). Immunofluorescence staining was used to detect the proportion of Mi/M phi in contact with apoptotic neurons, as well as neuronal damage. Results ASK1 was highly expressed in Mi/M phi during the acute phase of epilepsy. Conditional knockout of ASK1 in Mi/M phi markedly reduced the frequency of seizures in the acute phase and the frequency of spontaneous recurrent seizures (SRSs) in the chronic phase. In addition, ASK1 conditional knockout mice displayed long-term neurobehavioral improvements during the Y maze test and the three-chamber social novelty preference test. ASK1 selective knockout mitigated neuroinflammation, as evidenced by lower levels of Iba1(+)/CD16(+) proinflammatory Mi/M phi. Conditional knockout of ASK1 increased Mi/M phi proportion in contact with apoptotic neurons. Neuronal loss was partially restored by ASK1 selective knockout. Conclusion Conditional knockout of ASK1 in Mi/M phi reduced seizure severity, neurobehavioral impairments, and histological damage, at least via inhibiting proinflammatory microglia/macrophages responses. ASK1 in microglia/macrophages is a potential therapeutic target for inflammatory responses in epilepsy.

Automated summary

Conditional knockout of ASK1 in microglia/macrophages reduces seizure severity, improves neurobehavioral impairments, and mitigates histological damage, suggesting that ASK1 in microglia/macrophages is a potential therapeutic target for inflammatory responses in epilepsy.