NLRP3-Mediated Piezo1 Upregulation in ACC Inhibitory Parvalbumin-Expressing Interneurons Is Involved in Pain Processing after Peripheral Nerve Injury

Abstract

The anterior cingulate cortex (ACC) is particularly critical for pain information processing. Peripheral nerve injury triggers neuronal hyper-excitability in the ACC and mediates descending facilitation to the spinal dorsal horn. The mechanically gated ion channel Piezo1 is involved in the transmission of pain information in the peripheral nervous system. However, the pain-processing role of Piezo1 in the brain is unknown. In this work, we found that spared (sciatic) nerve injury (SNI) increased Piezo1 protein levels in inhibitory parvalbumin (PV)-expressing interneurons (PV-INs) but not in glutaminergic CaMKⅡ+ neurons, in the bilateral ACC. A reduction in the number of PV-INs but not in the number of CaMKⅡ+ neurons and a significant reduction in inhibitory synaptic terminals was observed in the SNI chronic pain model. Further, observation of morphological changes in the microglia in the ACC showed their activated amoeba-like transformation, with a reduction in process length and an increase in cell body area. Combined with the encapsulation of Piezo1-positive neurons by Iba1+ microglia, the loss of PV-INs after SNI might result from phagocytosis by the microglia. In cellular experiments, administration of recombinant rat TNF-α (rrTNF) to the BV2 cell culture or ACC neuron primary culture elevated the protein levels of Piezo1 and NOD-like receptor (NLR) family pyrin domain containing 3 (NLRP3). The administration of the NLRP3 inhibitor MCC950 in these cells blocked the rrTNF-induced expression of caspase-1 and interleukin-1β (key downstream factors of the activated NLRP3 inflammasome) in vitro and reversed the SNI-induced Piezo1 overexpression in the ACC and alleviated SNI-induced allodynia in vivo. These results suggest that NLRP3 may be the key factor in causing Piezo1 upregulation in SNI, promoting an imbalance between ACC excitation and inhibition by inducing the microglial phagocytosis of PV-INs and, thereby, facilitating spinal pain transmission.

Mechanosensing by Piezo1 and its implications in the kidney

“…TLR4 is a cell recognition receptor located on the cell membrane and is involved in the initiation of inflammation, whereas NLRP3 is located intracellularly and, when activated, promotes the assembly of inflammasomes and amplifies the inflammatory response, thereby maintaining inflammation (i.e., the pyroptosis-associated inflammatory response). [179][180][181] Piezo1 has been shown to mediate inflammatory responses through the activation of NLRP3 inflammasomes in several inflammatory diseases, 174,[182][183][184] but so far, no data have been reported on kidney injury. NF-kB has been shown to act as the upstream effector of NLRP3, thereby facilitating NLRP3 transcription and its assembly with ASC and pro-caspase 1.…”

Piezo1 and Its Function in Different Blood Cell Lineages

“…Piezo1 expression is also augmented in various cancers due to stiffness in the tumor microenvironment, causing further cell proliferation and migration [ 43 ]. Moreover, injury-mediated Piezo1 upregulation has been reported in the cases of peripheral nerve injury [ 44 ] and bone marrow irradiation injury [ 45 ]. Finally, metabolites such as Trimethylamine-N-oxide, a diet-derived metabolite that correlates positively with multiple chronic diseases, were shown to upregulate Piezo1 in chondrocytes and to correlate with the pathogenesis of osteoarthritis [ 46 ].…”

Stress/cell death pathways, neuroinflammation, and neuropathic pain

“…114 Piezo1 can be up-regulated by NLRP3 in SNI, facilitating unbalanced ACC excitation and suppression through triggering microglial phagocytosis of inhibitory parvalbumin-expressing interneurons, thus promoting spinal pain transmission. 114 Transmembrane protein 16F (TMEM16F) is a Ca 2+ -dependent ion channel and a phospholipid scramblase, which mediates microglial activation in neuropathic pain. 115 Mice with TMEM16F knockdown in microglia fail to experience mechanical hypersensitivity following nerve injury.…”

“…Peripheral nerve injury evokes neuronal hyperexcitability in the ACC and contributes descending promotion to the spinal dorsal horn. Piezo type mechanosensitive ion channel component 1 (Piezo1) participates in the delivery of pain information in the peripheral nervous system 114 . Piezo1 can be up‐regulated by NLRP3 in SNI, facilitating unbalanced ACC excitation and suppression through triggering microglial phagocytosis of inhibitory parvalbumin‐expressing interneurons, thus promoting spinal pain transmission 114 .…”

“…Piezo type mechanosensitive ion channel component 1 (Piezo1) participates in the delivery of pain information in the peripheral nervous system 114 . Piezo1 can be up‐regulated by NLRP3 in SNI, facilitating unbalanced ACC excitation and suppression through triggering microglial phagocytosis of inhibitory parvalbumin‐expressing interneurons, thus promoting spinal pain transmission 114 . Transmembrane protein 16F (TMEM16F) is a Ca 2+ ‐dependent ion channel and a phospholipid scramblase, which mediates microglial activation in neuropathic pain 115 .…”