Pathogenesis of spinal cord injury induced edema and neuropathic pain: expression of multiple isoforms of wnk1

Abstract

BackgroundNeuropathic pain (NP) is a common occurrence following spinal cord injury (SCI). Identification of specific molecular pathways that are involved in pain syndromes has become a major priority in current SCI research. We have investigated the role of a cation-dependent chloride transporter, Cl-regulatory protein Na+-K+-Cl- 1 (NKCC1), phosphorylation profile of NKCC1 and its specific involvement in neuropathic pain following contusion SCI (cSCI) using a rat model. Administration of the NKCC1 inhibitor bumetanide (BU) increases the mean hindpaw withdrawal latency time (WLT), thermal hyperalgesia (TH) following cSCI. These results demonstrate implication of NKCC1 co-transporter and BUin SCI-induced neuropathic pain. The with-no-lysine (K)–1 (WNK1) kinase has been shown to be an important regulator of NKCC1 phosphorylation in many systems, including nocioception. Mutations in a neuronal-specific exon of WNK1 (HSN2) was identified in patients that have hereditary sensory neuropathy type II (HSANII) also implicates WNK1 in nocioception, such that these patients have loss of perception to pain, touch and heat. In our ongoing research we proposed two studies utilizing our contusion SCI (cSCI) NP model of rat.PurposeStudy 1 aimed at NKCC1 expression and activity is up-regulated following cSCI in the early edema and chronic neuropathic pain phases. Study 2 aimed at identifying the expression profile of alternatively spliced WNK1 isoforms in animals exhibiting thermal hyperalgesia (TH) following cSCI.MethodsAdult male Sprague Dawley rats (275–300 g) following laminectomy received cSCI at T9 with the NYU impactor-device II by dropping 10 g weight from the height of 12.5 mm. Control rats obtained laminectomy but no impaction. Following injury, functional recovery was assessed by BBB locomotor scores on day 1, 7, 14, 21, 35, and 42 and development of thermal hyperalgesia on day 21, 28, 35, and 42 day of injury by monitoring hind paw withdraw latency time (WLT) in seconds compared with the baseline data before injury.ResultsIncreased NKCC1 may explain observed increase in magnetic resonance imaging (MRI) T2, exhibiting NKCC1 localization in neurons. This data supports NKCC1’s role in the pathogenesis of acute and chronic phases of injury, namely spinal cord edema and chronic phase neuropathic pain. NKCC1 dependent chloride influx requires the phosphorylation at specific residues. Probing for the HSN2 exon of WNK1 reveals two key findings: i) the HSN2 exon is found in alternatively spliced neuronal isoforms found at 250 kDa and 230 kDa; ii) the 250 kDa isoform is found only in tissue that is injured.ConclusionsThis data implicates the NKCC1/WNK1/WNK1HSN2 involvement in post-injury response that contributes to the development of neuropathic pain. Targeting this system may have therapeutic benefit.

Yoga: Can It Be Integrated with Treatment of Neuropathic Pain

“…Authors have speculated, through various grant proposals, that by inhibiting upregulation of such pain molecules in the early phase and/or late phase of injury, spinal cord damage and induced NP could be ameliorated. Our research findings from previous studies have helped in understanding novel mechanisms and treatments for SCI and NP employing a rat model [36][37][38][39][40][41][42] . This review aims to prompt new studies that examine the possible relationship of nociceptive proteins and its implications in translational approach of yogic processes in NP.…”

“…In many systems, including nociception, mutations in this kinase with the neuronal-specific exon of WNK1 in patients with hereditary sensory neuropathy type II show that patients with a mutation in nociception have a lessened awareness to pain, touch, and heat. The overall implication of NKCC1 and its activating kinase WNK1 shows their contribution in sensing and developing NP [37] . It will be interesting to investigate the relationship between NKCC1 and WNK1 upregulation as it relates to yoga practice.…”

Folic Acid Modulates Matrix Metalloproteinase-2 Expression, Alleviates Neuropathic Pain, and Improves Functional Recovery in Spinal Cord-Injured Rats

“…Sprague-Dawley male rats weighing 250-270 g received cSCI with a custom spinal cord impactor device that drops a 10 g weight from a height of 12.5 mm as described earlier [13][14][15][16][17][18][19][20] . Briefly, following the induction of inhalational anesthesia (isoflurane used with oxygen, induction 5%, maintenance 2.5%), T9 laminectomy was performed prior to impaction (online suppl.…”

“…We have adopted and established this as a sensitive and reliable behavior test as reported previously in several studies [13][14][15][16][17][18][19][20] . Briefly, animals were placed inside the Ugo Basile Plantar Test apparatus (Plantar TM Test, Stoelting, IL, USA) having a focused beam of radiant heat underneath their paws.…”

Immediate administration of COX inhibitors in spinal cord contusion injury and a current review of COX Therapy

“…Employing a rat model of contusion SCI, research in our lab has been focused on the use of cyclooxygenase 2 (COX-2) inhibitors during the acute phase of SCI [7]. Chronic phase studies of SCI-induced injuries, reviewed from our lab [8] focused on numerous pathways including the use of peroxisome proliferator-activated receptor (PPAR-gamma) agonists [9] ; COX-2 inhibitors [10,11]; vanilloid-1/ bradykinin-1 receptor antagonists [12]; phosphodiesterase-4 (PDE4) inhibitor, rolipram [13]; cannabinoid (CB1/CB2) receptors [14]; ion channel activity including NKCC1/KCC2 in the development of chronic NP [15][16][17][18].…”