Anti-allodynic and anti-inflammatory effects of 17α-hydroxyprogesterone caproate in oxaliplatin-induced peripheral neuropathy.

Chemotherapy-induced peripheral neuropathy is a disabling condition induced by several frequently used chemotherapeutic drugs including the front-line agent oxaliplatin (OXA). Symptoms are predominantly sensory with the development of neuropathic pain. Alternative dosing protocols and treatment discontinuation are the only available therapeutic strategies. The aim of our work was to evaluate the potential of a synthetic derivative of progesterone, 17α-hydroxyprogesterone caproate (HPGC), in the prevention and treatment of OXA-evoked painful neuropathy. We also evaluated glial activation at the dorsal root ganglia (DRG) and spinal cord levels as a possible target mechanism underlying HPGC actions. Male rats were injected with OXA and HPGC following a prophylactic (HPGCp) or therapeutic (HPGCt) scheme (starting either before or after chemotherapy). The development of hypersensitivity and allodynic pain and the expression of neuronal and glial activation markers were evaluated. When compared to control animals, those receiving OXA showed a significant decrease in paw mechanical and thermal thresholds, with the development of allodynia. Animals treated with HPGCp showed patterns of response similar to those detected in control animals, while those treated with HPGCt showed a suppression of both hypersensitivities after HPGC administration. We also observed a significant increase in the mRNA levels of activating transcription factor 3, the transcription factor (c-fos), glial fibrillary acidic protein, ionized calcium binding adaptor protein 1, interleukin 1 beta (IL-1ß) and tumor necrosis factor alpha (TNFα) in DRG and spinal cord of OXA-injected animals, and significantly lower levels in rats receiving OXA and HPGC. These results show that HPGC administration reduces neuronal and glial activation markers and is able to both prevent and suppress OXA-induced allodynia, suggesting a promising therapeutic strategy.

Effect of the urease-derived peptide Jaburetox on the central nervous system of Triatoma infestans (Insecta: Heteroptera).

BACKGROUND: Triatoma infestans is the main vector of Chagas'disease in Southern Cone countries. In triatomines, symptoms suggesting neurotoxicity were observed after treatment with Jaburetox (Jbtx), the entomotoxic peptide obtained from jackbean urease. Here, we study its effect in the central nervous system (CNS) of this species. METHODS: Immunohistochemistry, Western blots, immunoprecipitation, two-dimensional electrophoresis, tandem mass spectrometry and enzymatic assays were performed. RESULTS: Anti-Jbtx antibody labeled somata of the antennal lobe only in Jbtx-treated insects. Western blot assays of nervous tissue using the same antibody reacted with a 61kDa protein band only in peptide-injected insects. Combination of immunoprecipitation, two-dimensional electrophoresis and tandem mass spectrometry identified UDP-N-acetylglucosamine pyrophosphorylase (UDP-GlcNAcP) as a molecular target for Jbtx. The activity of UDP-GlcNAcP increased significantly in the CNS of Jbtx-treated insects. The effect of Jbtx on the activity of nitric oxide synthase (NOS) and NO production was investigated as NO is a recognized messenger molecule in the CNS of T. infestans. NOS activity and NO levels decreased significantly in CNS homogenates of Jbtx-treated insects. CONCLUSIONS: UDP-GlcNAcP is a molecular target of Jbtx. Jbtx impaired the activity of T. infestans nitrergic system, which may be related with early behavioral effects. GENERAL SIGNIFICANCE: We report that the CNS of Triatoma infestans is a target for the entomotoxic peptide and propose that a specific area of the brain is involved. Besides potentially providing tools for control strategies of Chagas' disease vectors our data may be relevant in various fields of research as insect physiology, neurobiology and protein function.

An update to pain management after spinal cord injury: from pharmacology to circRNAs.

Neuropathic pain (NP) following a spinal cord injury (SCI) is often hard to control and therapies should be focused on the physical, psychological, behavioral, social, and environmental factors that may contribute to chronic sensory symptoms. Novel therapeutic treatments for NP management should be based on the combination of pharmacological and nonpharmacological options. Some of them are addressed in this review with a focus on mechanisms and novel treatments. Several reports demonstrated an aberrant expression of non-coding RNAs (ncRNAs) that may represent key regulatory factors with a crucial role in the pathophysiology of NP and as potential diagnostic biomarkers. This review analyses the latest evidence for cellular and molecular mechanisms associated with the role of circular RNAs (circRNAs) in the management of pain after SCI. Advantages in the use of circRNA are their stability (up to 48 h), and specificity as sponges of different miRNAs related to SCI and nerve injury. The present review discusses novel data about deregulated circRNAs (up or downregulated) that sponge miRNAs, and promote cellular and molecular interactions with mRNAs and proteins. This data support the concept that circRNAs could be considered as novel potential therapeutic targets for NP management especially after spinal cord injuries.

Modulation of the Inflammatory Response by Pre-emptive Administration of IMT504 Reduces Postoperative Pain in Rats and has Opioid-Sparing Effects.

Despite the available knowledge on underlying mechanisms and the development of several therapeutic strategies, optimal management of postoperative pain remains challenging. This preclinical study hypothesizes that, by promoting an anti-inflammatory scenario, pre-emptive administration of IMT504, a noncoding, non-CpG oligodeoxynucleotide with immune modulating properties, will reduce postincisional pain, also facilitating therapeutic opioid-sparing. Male adult Sprague-Dawley rats with unilateral hindpaw skin-muscle incision received pre-emptive (48 and 24 hours prior to surgery) or postoperative (6 hours after surgery) subcutaneous vehicle (saline) or IMT504. Various groups of rats were prepared for pain-like behavior analyses, including subgroups receiving morphine or naloxone, as well as for flow-cytometry or quantitative RT-PCR analyses of the spleen and hindpaws (for analysis of inflammatory phenotype). Compared to vehicle-treated rats, pre-emptive IMT504 significantly reduced mechanical allodynia by 6 hours after surgery, and accelerated recovery of basal responses from 72 hours after surgery and onwards. Cold allodynia was also reduced by IMT504. Postoperative administration of IMT504 resulted in similar positive effects on pain-like behavior. In IMT504-treated rats, 3 mg/kg morphine resulted in comparable blockade of mechanical allodynia as observed in vehicle-treated rats receiving 10 mg/kg morphine. IMT504 significantly increased hindpaw infiltration of mesenchymal stem cells, CD4+T and B cells, and caused upregulated or downregulated transcript expressions of interleukin-10 and interleukin-1ß, respectively. Also, IMT504 treatment targeted the spleen, with upregulated or downregulated transcript expressions, 6 hours after incision, of interleukin-10 and interleukin-1ß, respectively. Altogether, pre-emptive or postoperative IMT504 provides protection against postincisional pain, through participation of significant immunomodulatory actions, and exhibiting opioid-sparing effects. PERSPECTIVE: This preclinical study introduces the noncoding non-CpG oligodeoxynucleotide IMT504 as a novel modulator of postoperative pain and underlying inflammatory events. The opioid-sparing effects observed for IMT504 appear as a key feature that could contribute, in the future, to reducing opioid-related adverse events in patients undergoing surgical intervention.

Progesterone receptor-mediated actions and the treatment of central nervous system disorders: An up-date of the known and the challenge of the unknown.

Progesterone has been shown to exert a wide range of remarkable protective actions in experimental models of central nervous system injury or disease. However, the intimate mechanisms involved in each of these beneficial effects are not fully depicted. In this review, we intend to give the readers a thorough revision on what is known about the participation of diverse receptors and signaling pathways in progesterone-mediated neuroprotective, pro-myelinating and anti-inflammatory outcomes, as well as point out to novel regulatory mechanisms that could open new perspectives in steroid-based therapies.

Spinal neuropeptide expression and neuropathic behavior in the acute and chronic phases after spinal cord injury: Effects of progesterone administration.

Patients with spinal cord injury (SCI) develop chronic pain that severely compromises their quality of life. We have previously reported that progesterone (PG), a neuroprotective steroid, could offer a promising therapeutic strategy for neuropathic pain. In the present study, we explored temporal changes in the expression of the neuropeptides galanin and tyrosine (NPY) and their receptors (GalR1 and GalR2; Y1R and Y2R, respectively) in the injured spinal cord and evaluated the impact of PG administration on both neuropeptide systems and neuropathic behavior. Male rats were subjected to spinal cord hemisection at T13 level, received daily subcutaneous injections of PG or vehicle, and were evaluated for signs of mechanical and thermal allodynia. Real time PCR was used to determine relative mRNA levels of neuropeptides and receptors, both in the acute (1day) and chronic (28days) phases after injury. A significant increase in Y1R and Y2R expression, as well as a significant downregulation in GalR2 mRNA levels, was observed 1day after SCI. Interestingly, PG early treatment prevented Y1R upregulation and resulted in lower NPY, Y2R and GalR1 mRNA levels. In the chronic phase, injured rats showed well-established mechanical and cold allodynia and significant increases in galanin, NPY, GalR1 and Y1R mRNAs, while maintaining reduced GalR2 expression. Animals receiving PG treatment showed basal expression levels of galanin, NPY, GalR1 and Y1R, and reduced Y2R mRNA levels. Also, and in line with previously published observations, PG-treated animals did not develop mechanical allodynia and showed reduced sensitivity to cold stimulation. Altogether, we show that SCI leads to considerable changes in the spinal expression of galanin, NPY and their associated receptors, and that early and sustained PG administration prevents them. Moreover, our data suggest the participation of galaninergic and NPYergic systems in the plastic changes associated with SCI-induced neuropathic pain, and further supports the therapeutic potential of PG- or neuropeptide-based therapies to prevent and/or treat chronic pain after central injuries.

Immunomodulatory oligonucleotide IMT504: Effects on mesenchymal stem cells as a first-in-class immunoprotective/immunoregenerative therapy.

The immune responses of humans and animals to insults (i.e., infections, traumas, tumoral transformation and radiation) are based on an intricate network of cells and chemical messengers. Abnormally high inflammation immediately after insult or abnormally prolonged pro-inflammatory stimuli bringing about chronic inflammation can lead to life-threatening or severely debilitating diseases. Mesenchymal stem cell (MSC) transplant has proved to be an effective therapy in preclinical studies which evaluated a vast diversity of inflammatory conditions. MSCs lead to resolution of inflammation, preparation for regeneration and actual regeneration, and then ultimate return to normal baseline or homeostasis. However, in clinical trials of transplanted MSCs, the expectations of great medical benefit have not yet been fulfilled. As a practical alternative to MSC transplant, a synthetic drug with the capacity to boost endogenous MSC expansion and/or activation may also be effective. Regarding this, IMT504, the prototype of a major class of immunomodulatory oligonucleotides, induces in vivo expansion of MSCs, resulting in a marked improvement in preclinical models of neuropathic pain, osteoporosis, diabetes and sepsis. IMT504 is easily manufactured and has an excellent preclinical safety record. In the small number of patients studied thus far, IMT504 has been well-tolerated, even at very high dosage. Further clinical investigation is necessary to demonstrate the utility of IMT504 for resolution of inflammation and regeneration in a broad array of human diseases that would likely benefit from an immunoprotective/immunoregenerative therapy.

Neuroactive steroids, nociception and neuropathic pain: A flashback to go forward.

The present review discusses the potential role of neurosteroids/neuroactive steroids in the regulation of nociceptive and neuropathic pain, and recapitulates the current knowledge on the main mechanisms involved in the reduction of pain, especially those occurring at the dorsal horn of the spinal cord, a crucial site for nociceptive processing. We will make special focus on progesterone and its derivative allopregnanolone, which have been shown to exert remarkable actions in order to prevent or reverse the maladaptive changes and pain behaviors that arise after nervous system damage in various experimental neuropathic conditions.

Progesterone modulates pro-inflammatory cytokine expression profile after spinal cord injury: Implications for neuropathic pain.

Neuropathic pain is a frequent complication of spinal cord injury (SCI), still refractory to conventional treatment. Glial cell activation and cytokine production contribute to the pathology of central neuropathic syndromes. In this study we evaluated the effects of progesterone, a neuroactive steroid, on pain development and the spinal expression of IL-1ß, its receptors (IL-1RI and IL-1RII) and antagonist (IL-1ra), IL-6 and TNFα, and NR1 subunit of NMDAR. Our results show that progesterone, by modulating the expression of pro-inflammatory cytokines and neuronal IL-1RI/NR1 colocalization, emerges as a promising agent to prevent chronic pain after SCI.

Temporal changes in the expression of the translocator protein TSPO and the steroidogenic enzyme 5α-reductase in the dorsal spinal cord of animals with neuropathic pain: Effects of progesterone administration.

Neuropathic pain is a frequent complication of spinal cord injury (SCI), still refractory to conventional treatment. The presence and biological activity of steroidogenic regulatory proteins and enzymes in the spinal cord suggests that neurosteroids locally generated could modulate pain messages. In this study we explored temporal changes in the spinal expression of the 18kDa translocator protein TSPO, the steroidogenic acute regulatory protein (StAr) and the steroidogenic enzyme 5α-reductase (5α-RI/II) in an experimental model of central chronic pain. Male Sprague-Dawley rats were subjected to a SCI and sacrificed at different time points (1, 14 or 28days). The development of mechanical and cold allodynia was assessed. Injured animals showed an early increase in the mRNA levels of TSPO and 5α-RII, whereas in the chronic phase a significant decrease in the expression of 5α-RI and 5α-RII was observed, coinciding with the presence of allodynic behaviors. Furthermore, since we have shown that progesterone (PG) administration may offer a promising perspective in pain modulation, we also evaluated the expression of steroidogenic proteins and enzymes in injured animals receiving daily injections of the steroid. PG-treated did not develop allodynia and showed a marked increase in the mRNA levels of TSPO, StAR, 5α-RI and 5α-RII 28days after injury. Our results suggest that in the acute phase after SCI, the increased expression of TSPO and 5α-RII may represent a protective endogenous response against tissue injury, which is not maintained in the chronic allodynic phase. PG may favor local steroidogenesis and the production of its reduced metabolites, which could contribute to the antiallodynic effects observed after PG treatment.

Progesterone prevents allodynia after experimental spinal cord injury.

UNLABELLED: Chronic pain after spinal cord injury represents a therapeutic challenge. Progesterone, a neuroprotective steroid, has been shown to modulate nociceptive thresholds, whereas its effect on neuropathic pain needs to be further explored. In this study, we evaluated whether progesterone could ameliorate pain-associated behaviors in animals subjected to a spinal cord hemisection. The development of mechanical and cold allodynia was assessed in injured male rats treated with daily injections of progesterone or vehicle. The expression of N-methyl-D-aspartate receptor (NMDAR) subunits, protein kinase C gamma (PKCγ), preprodynorphin (ppD), and kappa opioid receptor (KOR), key players in chronic pain mechanisms, was determined in the dorsal spinal cord. Twenty-eight days after injury, all vehicle-treated animals presented allodynic behaviors and a marked increase in NMDAR subunits, PKCγ, and ppD mRNA levels, with no changes in KOR mRNA levels. Progesterone prevented the development of mechanical allodynia and reduced the painful responses to cold stimulation. In correlation with the attenuation of pain behaviors, the steroid prevented NMDAR subunits and PKCγ mRNAs upregulation, did not modify the elevated ppD mRNA levels, but increased KOR expression. In conclusion, progesterone modulates neuropathic pain after spinal cord injury, creating a favorable molecular environment that may decrease spinal nociceptive signaling. PERSPECTIVE: The present study suggests that progesterone administration could represent an interesting strategy to modulate neuropathic pain circuits after spinal cord injury. Further studies are needed to investigate the potential progesterone receptors involved in these actions.

Distribution and characterization of nitric oxide synthase in the nervous system of Triatoma infestans (Insecta: Heteroptera).

The biochemical characterization of nitric oxide synthase (NOS) and its distribution in the central nervous system (CNS) were studied in the heteropteran bug Triatoma infestans. NOS-like immunoreactivity was found in the brain, subesophageal ganglion, and thoracic ganglia by using immunocytochemistry. In the protocerebrum, NOS-immunoreactive (IR) somata were detected in the anterior, lateral, and posterior soma rinds. In the optic lobe, numerous immunostained somata were observed at the level of the first optic chiasma, around the lobula, and in the proximal optic lobe. In the deutocerebrum, NOS-IR perikarya were mainly observed in the lateral soma rind, surrounding the sensory glomeruli, and a few cell bodies were seen in association with the antennal mechanosensory and motor neuropil. No immunostaining could be detected in the antennal nerve. The subesophageal and prothoracic ganglia contained scattered immunostained cell bodies. NOS-IR somata were present in all the neuromeres of the posterior ganglion. Western blotting showed that a universal NOS antiserum recognized a band at 134 kDa, in agreement with the expected molecular weight of the protein. Analysis of the kinetics of nitric oxide production revealed a fully active enzyme in tissue samples of the CNS of T. infestans.