Enhanced T-type calcium channel 3.2 activity in sensory neurons contributes to neuropathic-like pain of monosodium iodoacetate-induced knee osteoarthritis

Abstract

The monosodium iodoacetate knee osteoarthritis model has been widely used for the evaluation of osteoarthritis pain, but the pathogenesis of associated chronic pain is not fully understood. The T-type calcium channel 3.2 (CaV3.2) is abundantly expressed in the primary sensory neurons, in which it regulates neuronal excitability at both the somata and peripheral terminals and facilitates spontaneous neurotransmitter release at the spinal terminals. In this study, we investigated the involvement of primary sensory neuron-CaV3.2 activation in monosodium iodoacetate osteoarthritis pain. Knee joint osteoarthritis pain was induced by intra-articular injection of monosodium iodoacetate (2 mg) in rats, and sensory behavior was evaluated for 35 days. At that time, knee joint structural histology, primary sensory neuron injury, and inflammatory gliosis in lumbar dorsal root ganglia, and spinal dorsal horn were examined. Primary sensory neuron-T-type calcium channel current by patch-clamp recording and CaV3.2 expression by immunohistochemistry and immunoblots were determined. In a subset of animals, pain relief by CaV3.2 inhibition after delivery of CaV3.2 inhibitor TTA-P2 into sciatic nerve was investigated. Knee injection of monosodium iodoacetate resulted in osteoarthritis histopathology, weight-bearing asymmetry, sensory hypersensitivity of the ipsilateral hindpaw, and inflammatory gliosis in the ipsilateral dorsal root ganglia, sciatic nerve, and spinal dorsal horn. Neuronal injury marker ATF-3 was extensively upregulated in primary sensory neurons, suggesting that neuronal damage was beyond merely knee-innervating primary sensory neurons. T-type current in dissociated primary sensory neurons from lumbar dorsal root ganglia of monosodium iodoacetate rats was significantly increased, and CaV3.2 protein levels in the dorsal root ganglia and spinal dorsal horn ipsilateral to monosodium iodoacetate by immunoblots were significantly increased, compared to controls. Perineural application of TTA-P2 into the ipsilateral sciatic nerve alleviated mechanical hypersensitivity and weight-bearing asymmetry in monosodium iodoacetate osteoarthritis rats. Overall, our findings demonstrate an elevated CaV3.2 expression and enhanced function of primary sensory neuron-T channels in the monosodium iodoacetate osteoarthritis pain. Further study is needed to delineate the importance of dysfunctional primary sensory neuron-CaV3.2 in osteoarthritis pain.

Piezo2 mechanosensitive ion channel is located to sensory neurons and non-neuronal cells in rat peripheral sensory pathway: implications in pain

“…Since the spinal cord DH receives innervation from DRG-PSNs, we next evaluated by IHC whether CFA pain was associated with altered Piezo2 expression in the DH. For quantitative comparison, we normalized Piezo2-IR intensity on the side ipsilateral to CFA by using the contralateral side in the same section as the control [14, 57], assuring that all IHC preparation and image capture parameters are identical in the same cross-section. To validate the use of general IR intensity of the DH as a quantitative indicator of protein expression in sensory neurons, we compared IB4 and CGRP staining in the DH from SNI rats, in which quantitatively decreased IB4 and CGRP immunoreactive intensity in sensory neurons ipsilateral to the SNI injury is expected [37, 80].…”

“…Lumbar spinal cord sections from control rats and from rats subjected to CFA inflammatory pain, as well as archival spinal cord sections from neuropathic pain models of SNL, SNI, and TNI (4wk post injury), and MIA-OA pain (5wk after MIA knee injection), as previously reported [37, 57-59, 80, 81], were used to evaluate whether pain is associated with alteration of Piezo2 expression in the DH. For quantification of DH piezo2 immunostaining, the Image J v.1.46 was used to quantify changes in immunolabeled fluorescent intensities as described previously [14, 57], with some minor modifications. In brief, the sections with symmetrical width of DH throughout the mediolateral axis were used for measurement, and the upper and lower threshold optical intensities were adjusted to encompass and match the immunoreactivity (IR) that appears in red.…”

The Mechanisms of Plasticity of Nociceptive Ion Channels in Painful Diabetic Neuropathy

“…Several studies have shown that the expression of Ca V 3.2 channels is increased in spinal dorsal horn or DRG neurons in models of chronic nerve injury ( 46 – 51 ), inflammatory pain models ( 52 – 56 ), acute pain model ( 57 ) as well as in chemically induced neuropathies ( 58 ) including diabetic neuropathy ( 40 , 59 ).…”

The Role of Ionic Currents in Peripheral Nerve Regeneration

“…Expression in cell membranes of T-type CaV3.2 calcium channels and their activation in the dorsal root ganglion (DRG) damaged neurons in mice with neuropathic pain increase after spared nerve injury. Antisense inhibition may decrease mechanical allodynia 14 days after spared nerve injury, suggesting that CaV3.2 T-type calcium channels play a role in damaged DRG-mediated neurons (66). The CaV3.2 membranes of medium-sized DRG neurons play a considerable function in neuropathic pain (67).…”