The effect of the "segment" of spinal cord injury on the activity of the nucleotide-binding domain-like receptor protein 3 inflammasome and response to hormonal therapy.

Spinal cord injury (SCI) is a common devastating condition that causes neuronal loss and dysfunction. Neuroinflammation takes cardinal roles in the pathogenesis of SCI, and nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome is a mediator of inflammatory reactions occurring in SCI patients. The present study was designed to survey possible relation between thoracic segments whereby injury occurs with the activity of NLRP3 inflammasome complex, and to find the influence of hormonal therapy on the outcomes. Adult male Wistar rats underwent contusion SCI model at three different thoracic segments T1, T6 and T12, then receiving subcutaneous injection of either 10 mg/kg melatonin or 25 µg/kg 17-ß estradiol (E2) every 12 hours until 72 hours post-SCI. Inflammasome activity was assessed before and at the end of hormonal therapy. SCI rats showed decreased locomotor activity and myelination, and increased activity of the NLRP3, apoptosis-associated speck-like protein (ASC) and caspase-1 at gene and protein levels. Release of interleukins (ILs) 18 and 1ß was also augmented after SCI (P < 0.0.5). Hormonal therapy was most effective for targeting mRNA activity at T6 segment. Treatment with either melatonin or E2 caused a decrease in the protein activity of NLRP3 inflammasome at all segments (P < 0.0.5), except for T6 that NLRP3 protein had no response to melatonin. IL-1ß showed decreased activity in response to hormonal therapy at all segments, whilst IL-18 protein had no change at T1 segment. It is understood that although no alteration in the activity of NLRP3 was found for SCI at different segments, the response to hormonal therapy was influenced by segment. SIGNIFICANCE OF THE STUDY: From our results, the NLRP3 inflammasome activity is not influenced by segment, but there are differences in the effect of hormonal therapy on inflammasome activity at different segments in response to melatonin or E2. These findings also provide the beneficial effects of melatonin or E2 on inflammation caused by spinal cord injury in different thoracic segments. Finally, these data can have therapeutic importance for hormone therapy of spinal cord injury.

The expressions of NLRP1, NLRP3, and AIM2 inflammasome complexes in the contusive spinal cord injury rat model and their responses to hormonal therapy.

Spinal cord injury (SCI) is a devastating condition with a growing incidence in developing countries. The activity of inflammasome complexes initiates neuroinflammation, which is a key player in SCI pathogenesis. Here, NLRP1, NLRP3, and absent in melanoma 2 (AIM2) inflammasome complexes were assessed in the contusive (T6) SCI rats for their expression profiles and their response to hormonal therapy (10 mg/kg melatonin or 25 µg/kg 17ß-estradiol [E2] every 12 h until 72 h). Two phases was considered in this study: the dominant time of inflammasome activation, which was 72 h post-SCI and the response from each complex to hormonal therapy at this time. Gene and protein expressions of NLRP1, NLRP3, AIM2, ASC, and caspase-1 were evaluated by real-time PCR (for gene analysis), western blot, and immunohistochemistry (IHC), and biochemical presence of IL-18 and IL-1ß in spinal cord tissue homogenates was analyzed by enzyme-linked immunosorbent assay (ELISA). The whole inflammasome complexes showed high expressions in the SCI group, while after hormonal therapy, these alterations were counteracted, which were more conspicuous for the NLRP1 and NLRP3. Melatonin had no predilection over E2 for such effect. Finally, the expression profile of signaling related to the synthesis (TLR4/NF-κB) and activation (NADPH oxidase 2 [NOX2]/TXNIP) of inflammasome complexes was surveyed, and there were low activities for the two pathways in SCI rats that underwent hormone therapy. From the findings, it is concluded that both melatonin and E2 are efficient to target inflammasome activation in the SCI rats.