Phase 2 trial of montelukast for prevention of pain in sickle cell disease.

Cysteinyl leukotrienes (CysLTs) are lipid mediators of inflammation. In patients with sickle cell disease (SCD), levels of CysLTs are increased compared with controls and associated with a higher rate of hospitalization for pain. We tested the hypothesis that administration of the CysLT receptor antagonist montelukast would improve SCD-related comorbidities, including pain, in adolescents and adults with SCD. In a phase 2 randomized trial, we administered montelukast or placebo for 8 weeks. The primary outcome measure was a >30% reduction in soluble vascular cell adhesion molecule 1 (sVCAM), a marker of vascular injury. Secondary outcome measures were reduction in daily pain, improvement in pulmonary function, and improvement in microvascular blood flow, as measured by laser Doppler velocimetry. Forty-two participants with SCD were randomized to receive montelukast or placebo for 8 weeks. We found no difference between the montelukast and placebo groups with regard to the levels of sVCAM, reported pain, pulmonary function, or microvascular blood flow. Although montelukast is an effective treatment for asthma, we did not find benefit for SCD-related outcomes. This clinical trial was registered at www.clinicaltrials.gov as #NCT01960413

Sinomenine as a novel analgesic : mechanisms and applications

Chronic pain of various origins is a major health care issue affecting a large patient population, also bring significant social and economic cost on the society. Work presented in this thesis concerns novel methods of treatments for chronic pain using experimental models. Sinomenine is a chemical compound isolated originally from the root of the plant Sinomenium Acutum native to China and Japan. It is an alkaloid, structurally belongs to the morphine family. The root of Sinomenium Acutum, known as Qingteng, has been traditionally used in China as a medical remedy for condition likely to be rheumatism. Sinomenine is currently approved in China as an anti-rheumatic agent for clinical sue. In first part of the thesis, we studied the analgesic effect of sinomenine in chronic experimental pain models of neuropathic and arthritic pain. We showed that sinomenine has significant analgesic effects in rat and mouse models of neuropathic pain as well as in a mouse model (collagen antibody-induced arthritis model, CAIA) of arthritic pain. More importantly, the effect of sinomenine on neuropathic and arthritic pain is maintained upon repeated chronic administration without signs of tolerance or dependence. In the second part of the thesis, we examined the possible application of sinomenine as an analgesic, we showed that combination with sinomenine with gabapentin, a clinically used drug treating neuropathic pain, produced marked synergistic interaction in rat and mouse models of neuropathic pain and such synergism can still be observed upon repeated administration without signs of tolerance and dependence. We can also show a similar synergistic interaction between gabapentin and dextromethorphan, a low affinity non-competitive NMDA antagonist. The work presented in this thesis suggested that sinomenine could be explored as a novel analgesic in treating neuropathic and arthritic pain. The results also showed combination therapy involving sinomenine, gabapentin and dextromethorphan might be useful in the clinic. The potential mechanisms for the effect of sinomenine and its interaction with other analgesics need to be further studied

Sex differences in acute and chronic experimental pain models

Sex differences in response to noxious stimuli and in the development of chronic pain have been increasingly recognized and studied in humans and laboratory animals. In the clinic, extensive evidence indicates that there are a large number of chronic pain conditions that have higher prevalence in women than in men and some of these conditions, such as migraine and temporomandibular pain disorder, are also affected by the menstrual cycle. The mechanisms for sex differences in pain, particular in chronic pain, are largely unknown. The work presented in this thesis aims to explore mechanisms of sex differences using experimental pain models in rodents. In the first part of the thesis, we explored the role of estrogen receptors and the adenosine A2A receptor in sex differences in pain using genetically modified mice. We observed that in wild-type controls for estrogen receptor α or β knock-outs, females were significantly more sensitive than males to mechanical stimulation under normal condition and after carrageenan-induced inflammation. Such sex differences were eliminated in mice lacking either estrogen receptor α or β. Mechanical hypersensitivity resulting from partial sciatic nerve injury did not however differ between the sexes or between the wild-types and both estrogen receptor knock-outs. These results suggest that estrogen receptors α or β play a role in sex difference in basal mechanical pain threshold and inflammatory hypersensitivity. There was no sex difference in baseline mechanosensitivity in mice lacking the adenosine A2A receptor and wild-type controls. Carrageenan-induced mechanical hypersensitivity was significantly reduced in the A2A receptor knock-outs compared to wild-types. ZM-241,385, a selective A2A receptor antagonist, reduced inflammatory hypersensitivity in wild-type females, but not in males. The selective A2A receptor agonist CGS 21680 produced significantly more hypersensitivity in wild-type female mice than in males. These results suggest that activation of peripheral adenosine A2A receptors contributes to inflammatory hypersensitivity and that this effect is more prominent in females than in males. The second part of the thesis deals with the development of neuropathic pain-like behaviors (allodynia) in rats after spinal cord or infraorbital nerve injury. We observed a significant sex difference (females > males) in the development of mechanical allodynia after spinal cord injury in rats independent of the extent of injury. Increased mechanical hypersensitivity in females was not related to estrous stage at the time of injury. Similarly, after infraorbital nerve injury, female rats developed more persistent local and spread mechanical allodynia which was also not influenced by the estrous stages at the time or after injury. These studies provide further evidence for the presence of sex difference in baseline mechanical pain threshold, inflammatory hypersensitivity and experimental neuropathic pain in rodents. Furthermore, our results showed that estrogen receptors and adenosine A2A receptor may be involved in sex difference in pain sensitivity under normal condition or after inflammation. Finally, although female rats developed more persistent allodynia-like behaviors after spinal cord or infraorbital nerve injury, there appears to be no impact of the estrous cycle on pain development

A Review of Low-Level Laser Therapy for Spinal Cord Injury: Challenges And Safety

Introduction: Damage to the spinal cord is a central nervous system disorder that results in direct damage to neural cells (axons, cell bodies) and glia, followed by autonomic, motor and sensory impairments. Inflammatory response after this injury can contribute to secondary tissue damage that leads to further behavioral and functional disorders. Inflammation is a complex process, which occurs after an injury. If this progressive process is not well controlled can lead to additional damage to the spinal cord which is preventing neural improvement and regeneration and, which ultimately will not provide good clinical consequences. Inflammation in the injured spinal cord is a physiological response that causes the death of glial and neuronal cells. The reduction of the initial inflammatory process after damage to the spinal cord is one of the important therapeutic strategies. It has been proposed that low-level laser (LLL) therapy, as a noninvasive manner, can modulate inflammatory processes, which leads to a significant improvement in neurological symptoms after spinal cord injury (SCI).Methods: A comprehensive review was performed on SCI, the etiologies, and treatment methods using the keywords spinal cord injury, low-level laser, and inflammation in valid medical databases such as Google Scholar, PubMed, and Elsevier (76 articles). Among the collected papers, articles that were most relevant to the purposes of the study were selected and studied.Results: LLL therapy was able to reduce inflammation and also attenuate neuronal damage after spinal cord damage.Conclusion: In conclusion, the present study illustrates that LLL therapy has positive effects on improving functional recovery and regulating the inflammatory function in the SCI

Cytokine Dynamics, Diagnosis and Treatment of Neuroinflammation In Chronic Constriction Injury Rat Model

Chronic neuropathic pain is a serious, worldwide health problem leading to life-long treatment and the possibility of significant disability. In this study, neuropathic pain was modeled using the chronic constriction injury (CCI) in rats. The CCI rats exhibited hypersensitivity (typical neuropathic pain symptom) to mechanical stimulation of the affected paw 11 days post-surgery, at a time when sham surgery animals did not. It is known that immune cells play a role in the development of neuropathic pain and to further explore the relationship between neuropathic pain and immune cells, we hypothesized that the infiltration of immune cells into the affected sciatic nerve can be monitored in vivo by optical imaging. To test this hypothesis, an intravenous injection of a novel perfluorocarbon (PFC) nanoemulsion developed by J. M. Janjic (PharmD, PhD) and co-workers was used. Post-injection, the nanoemulsion is endocytosed by inflammatory cells (e.g. monocytes and macrophages) in a CCI rat. The nanoemulsion carried two distinct imaging agents, a near-infrared (NIR) lipophilic fluorescence reporter (DiR) and a 19F magnetic resonance imaging (MRI) tracer (PFC). This study showed that in live rats, NIR fluorescence was concentrated in the area of the affected sciatic nerve. Furthermore, the 19F MRI signal was observed in the affected sciatic nerve in the perfusion fixed rats. Histological examination of the CCI sciatic nerve sections revealed significant infiltration of CD68 positive macrophages. These results demonstrate that the infiltration of immune cells into the sciatic nerve can be visualized in live animals using these methods. Using the same strategy, a theranostic nanoemulsion containing an anti-inflammatory drug, celecoxib, along with NIR dye and 19F tracer, was used for the targeted delivery of the drug into the inflammatory cells at the site of injury while at the same time providing the ability to track inflammation. A single intravenous injection of the nanoemulsion carrying a low dose of celecoxib (0.24 mg/kg), a normally highly insoluble drug, appears to have provided a direct delivery of the drug into the inflammatory cells. Single dose intravenous injection of the theranostic nanoemulsion resulted in significant relief from the hypersensitivity behavior (mechanical allodynia) that persisted for at least four days post-injection. These findings demonstrated that celecoxib-containing theranostic nanoemulsion based therapy is an effective tool for the simultaneous tracking and treatment of the neuroinflammation in a CCI rat model. Inflammation is known to be associated with peripheral neuropathy, however the interplay among cytokines, chemokines and neurons is still unclear. We hypothesized that the neuroinflammatory interaction can be defined by using a computational modeling approach, based on the dynamics of the protein expression of various inflammatory mediators in the sciatic nerve of the CCI rats. Using Dynamic Bayesian Network inference, we identified Interleukin (IL)-18 as a central node associated with neuropathic pain in the CCI rat model. Immunofluorescence supported a role for inflammasome activation and induction of IL-18 at the site of injury. Combined in-vivo and in-silico approaches may thus highlight novel molecular targets associated with peripheral neuropathy that can be the target of future theranostic nanoemulsion-based therapy

PROTEIN KINASE A AND EPAC MEDIATE CHRONIC PAIN AFTER INJURY: PROLONGED INHIBITION BY ENDOGENOUS Y1 RECEPTORS IN DORSAL HORN

Inflammation or nerve injury sensitizes several populations of nociceptive neurons in the dorsal horn of the spinal cord, including those that express the neuropeptide Y (NPY) Y1 receptor (Y1R). Our overall hypothesis is that after tissue or nerve injury, these Y1R-expressing neurons enter a state of latent sensitization (LS) that contributes to vulnerability to the development of chronic pain; furthermore, LS is under the tonic inhibitory control of endogenous Y1R signaling. First, we evaluated the intracellular signaling pathways that become activated in Y1R-expressing neurons and participate in LS. To do this, we established behavioral models of inflammatory or neuropathic pain, allowed pain hypersensitivity to resolve, and then during this period of pain remission we administered the Y1R receptor antagonist, BIBO3304, by intrathecal injection. As observed previously with mu-opioid receptor antagonists/inverse agonists, we found that BIBO3304 reinstated pain hypersensitivity via an N-methyl-D-aspartate receptor (NMDAR)- and adenylyl cyclase type 1 (AC1)-dependent mechanism. Our subsequent behavioral pharmacological experiments then established two signaling pathways downstream of AC1 that maintain LS. The first pathway involves protein kinase A (PKA) and transient receptor potential cation channel A1 (TRPA1) and channel V1 (TRPV1). The second pathway involves exchange proteins activated by cAMP (Epac 1 and Epac 2). We next found that nerve injury decreases the co-expression of Y1R with markers of excitatory interneurons, suggesting that Y1R-expressing neurons acquire a pain-enhancing phenotype after peripheral nerve injury. In a separate set of experiments that utilized Y1R-receptor internalization as an index of NPY release, we found that nerve injury increased stimulus-evoked NPY release. We conclude that injury induces pain-facilitatory mechanisms of LS in the dorsal horn involving PKA→TRPA1 and PKA→TRPV1 at the central terminals of primary afferent neurons. Whether Epac mechanisms are located on these same presynaptic terminals and/or at Y1R-expressing excitatory interneurons remain to be determined. We also conclude that injury-induced LS is masked by a compensatory up-regulation of spinal NPY release that tonically inhibits pain. These results present a novel mechanism of injury-induced LS and endogenous control of the transition from acute to chronic pain by the NPY-Y1R system. Our work sheds light on novel targets for the treatment of chronic pain