The role of the peripheral nervous system in immune cell recruitment

Electroacupuncture Alleviates Pain-Related Emotion by Upregulating the Expression of NPS and Its Receptor NPSR in the Anterior Cingulate Cortex and Hypothalamus

Objective

Electroacupuncture (EA) is reported effective in alleviating pain-related emotion; however, the underlying mechanism of its effects still needs to be elucidated. The NPS-NPSR system has been validated for the involvement in the modulation of analgesia and emotional behavior. Here, we aimed to investigate the role of the NPS-NPSR system in the anterior cingulate cortex (ACC), hypothalamus, and central amygdala (CeA) in the use of EA to relieve affective pain modeled by complete Freund's adjuvant- (CFA-) evoked conditioned place aversion (C-CPA). Materials and Methods. CFA injection combined with a CPA paradigm was introduced to establish the C-CPA model, and the elevated O-maze (EOM) was used to test the behavioral changes after model establishment. We further explored the expression of NPS and NPSR at the protein and gene levels in the brain regions of interest by immunofluorescence staining and quantitative real-time PCR.

Results

We observed that EA stimulation delivered to the bilateral Zusanli (ST36) and Kunlun (BL60) acupoints remarkably inhibited sensory pain, pain-evoked place aversion, and anxiety-like behavior. The current study showed that EA significantly enhanced the protein expression of this peptide system in the ACC and hypothalamus, while the elevated expression of NPSR protein alone was just confined to the affected side in the CeA. Moreover, EA remarkably upregulated the mRNA expression of NPS in CeA, ACC, and hypothalamus and NPSR mRNA in the hypothalamus and CeA.

Conclusions

These data suggest the effectiveness of EA in alleviating affective pain, and these benefits may at least partially be attributable to the upregulation of the NPS-NPSR system in the ACC and hypothalamus.

Enhanced expression of neuropeptide S (NPS) receptor in eosinophils from severe asthmatics and subjects with total IgE above 100IU/ml

Eosinophils are inflammatory cells of particular relevance to asthma exacerbations. Neuropeptide S (NPS) receptor was identified in a search for asthma susceptibility genes, where the risk haplotypes of the NPS receptor gene associated with total serum IgE above 100IU/ml and asthma. The aim of the present study was to investigate and compare expression of NPS receptor in human peripheral blood eosinophils derived from subjects with total serum IgE above and below 100IU/ml and patients with different phenotypes of asthma. Additionally, we aimed to study the function of NPS receptor in human eosinophils. We found higher NPS receptor protein expression in eosinophils derived from subjects with high IgE when compared to those from subjects with low IgE and the level of NPS receptor positively correlated with serum IgE. NPS receptor expression was also higher in eosinophils from patients with severe asthma than in cells from mild asthmatics or healthy controls. The receptor agonist NPS was a chemotactic agent for eosinophils. NPS also increased N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated CD11b integrin levels in eosinophils from subjects with high IgE. Furthermore, eosinophils from those subjects exhibited Ca(2+) mobilization but not cAMP rise in response to NPS. Altogether, NPS receptor may have a pathological role in individuals with severe asthma and/or elevated serum IgE levels as eosinophils from these patients express higher levels of NPS receptor protein and respond to NPS by enhanced migration and adhesion molecule expression.

Neuropeptide S stimulates human monocyte chemotaxis via NPS receptor activation

Neuropeptide S (NPS) produces several biological actions by activating a formerly orphan GPCR, now named NPS receptor (NPSR). It has been previously demonstrated that NPS stimulates murine leukocyte chemotaxis in vitro. In the present study we investigated the ability of NPS, in comparison with the proinflammatory peptide formyl-Met-Leu-Phe (fMLP), to stimulate human monocyte chemotaxis. At a concentration of 10(-8)M fMLP significantly stimulated chemotaxis. NPS produced a concentration dependent chemotactic action over the concentration range 10(-12) to 10(-5)M. The NPSR antagonists [D-Cys((t)Bu)(5)]NPS, [(t)Bu-D-Gly(5)]NPS and SHA 68 were used to pharmacologically characterize NPS action. Monocyte chemoattractant effect of NPS, but not fMLP, was completely blocked by either peptide antagonists or SHA with the nonpeptide molecule being more potent. None of the NPSR antagonists modified per se random cell migration. Thus, the present study demonstrated that NPS is able to stimulate human monocyte chemotaxis and that this effect is entirely due to selective NPSR activation.

Dorsal root compression produces myelinated axonal degeneration near the biomechanical thresholds for mechanical behavioral hypersensitivity

Increased sensitivity to mechanical stimuli produced by transient cervical nerve root compression is dependent on the severity of applied load. In addition, trauma in the nervous system induces local inflammation, Wallerian degeneration, and a host of other degenerative processes leading to axonal dysfunction. Here, axonal degeneration and inflammation were assessed following transient dorsal root compression to establish a relationship between conditions for dorsal root axonal changes and those previously established for the onset and maintenance of mechanical behavioral hypersensitivity (26.3 mN and 38.2 mN, respectively). Compression loads were applied over a range (0-110 mN) known to produce sustained behavioral hypersensitivity. CD68- and NF200-immunoreactivity, as well as axonal pathological changes, were assessed in the dorsal root to investigate the load thresholds requisite for inducing macrophage infiltration and axonal degeneration relative to those thresholds for producing the onset and persistence of behavioral hypersensitivity. Neurofilament accumulation and the depletion of NF200-immunoreactivity in the region of compressed tissue were produced for loads that produce mechanical behavioral hypersensitivity. A 50th-percentile load threshold was determined (31.6 mN) governing the onset of NF200 depletion. However, CD68-immunoreactivity was increased for nearly all loads, suggesting that macrophage recruitment may not be directly related to nerve root-mediated behavioral hypersensitivity. This study provides new evidence for threshold-mediated degenerative changes in the context of behavioral hypersensitivity following nerve root compression.

Human peripheral blood mononuclear cells produce pre-pro-nociceptin/orphanin FQ mRNA

BACKGROUND

Peripheral blood mononuclear cells (PBMC) transcribe mRNA for the nonclassical opioid nociceptin/orphanin FQ (N/OFQ) receptor (NOP). We probed for the N/OFQ precursor, pre-pro-N/OFQ (ppN/OFQ).

METHODS

Using PBMC from 10 healthy volunteers we probed for ppN/OFQ using polymerase chain reaction (PCR) based experimental paradigms.

RESULTS

In gel-based PCR, we detected amplicons consistent with ppN/OFQ mRNA in all samples. This was confirmed in quantitative real-time PCR with cycle thresholds (representing quantity of mRNA) of 30.91 +/- 0.18 (n = 10).

CONCLUSIONS

These data indicate that PBMCs transcribe ppN/OFQ which, coupled with NOP expression, suggest NOP may be involved in the autoregulation of PBMCs.

Human peripheral blood mononuclear cells express nociceptin/orphanin FQ, but not mu, delta, or kappa opioid receptors

BACKGROUND

Expression of opioid receptors on peripheral blood mononuclear cells (PBMC) is controversial. These receptors are currently classified as classical (MOP/mu/mu, DOP/delta/delta and KOP/kappa/kappa) and nonclassical NOP (nociceptin/orphanin FQ; N/OFQ).

METHODS

In this volunteer study we probed for the expression of both classical and nonclassical opioid receptors using 1) radioligand binding, 2) specific antibody binding, and 3) polymerase chain reaction-based experimental paradigms.

RESULTS

Membranes prepared from PBMC from healthy volunteers did not bind either [3H]diprenorphine (a nonselective radioligand for classical opioid receptors) or [3H]N/OFQ. There was significant concentration-dependent binding of each radioligand to control tissues expressing recombinant MOP and NOP. In addition, using fluorescence-activated cell sorting paradigms, there was no binding of fluorescent naloxone or either of two MOP antibodies to whole PBMC, though fluorescent naloxone did bind to recombinant MOP (as a positive control). Using primers specific for classical and nonclassical opioid receptors, and RNA extracted from the PBMC of 10 healthy volunteers, we were also unable to detect MOP, DOP, and KOP transcripts. In contrast, NOP was detected in all samples.

CONCLUSIONS

Despite using several complementary experimental strategies, we failed to demonstrate protein for classical or nonclassical opioid receptors on PBMC from healthy volunteers. We detected NOP mRNA, suggesting low-density NOP expression on these immunocytes. It is possible that N/OFQ, produced by the PBMC itself, may be involved in the control of immune function.

Influence of pain treatment by epidural fentanyl and bupivacaine on homing of opioid-containing leukocytes to surgical wounds

Endogenous opioids released from leukocytes extravasating into injured tissue can interact with peripheral opioid receptors to inhibit nociception. Animal studies have shown that the homing of opioid-producing leukocytes to the injured site is modulated by spinal blockade of noxious input. This study investigated whether epidural analgesia (EDA) influences the migration of beta-endorphin (END) and/or met-enkephalin (ENK)-containing leukocytes into the subcutaneous wound tissue of patients undergoing abdominal surgery. In part I patients received general anesthesia combined either with intra- and postoperative EDA (with bupivacaine and fentanyl) or with postoperative patient controlled intravenous analgesia (PCIA; with the opioid piritramide). In part II patients received general anesthesia combined with either epidural fentanyl or bupivacaine which was continued postoperatively. Samples of cutanous and subcutanous tissue were taken from the wound site at the beginning, at the end and at various times after surgery, and were examined by immunohistochemistry for the presence of END and ENK. We found that (i) epidural bupivacaine, fentanyl and PCIA provided similar and clinically acceptable postoperative pain relief; (ii) compared to PCIA, epidural bupivacaine or fentanyl did not change the gross inflammatory reaction within the surgical wound; (iii) opioid-containing leukocytes were almost absent in normal subcutaneous tissue but migrated to the inflamed wound tissue in ascending numbers within a few hours, reaching a peak at about 24 h after surgery; (iv) compared to PCIA, EDA resulted in significantly decreased homing of END-containing leukocytes to the injured site at 24 h after surgery; and (v) the magnitude of this decrease was similar regardless of the epidural medication. These findings suggest that nociceptive but not sympathetic neurons are primarily involved in the attraction of opioid-containing leukocytes during early stages of inflammation.

Neurogenic factors in the impaired healing of diabetic foot ulcers

BACKGROUND

We hypothesize that the reduced innervation of skin can be observed both in clinically neuropathic and non-neuropathic diabetic foot ulcers and can contribute to low inflammatory cell infiltration.

MATERIALS AND METHODS

Twenty patients with type 2 diabetes and active foot ulcers, without clinical evidence of peripheral sensory neuropathy (n = 12) and with sensory neuropathy (n = 8) were involved in this study. Biopsies from ulcer margin were examined immunohistochemically.

RESULTS

Studies revealed presence of protein gene product 9.5 (PGP9.5)+ nerve endings only in reticular dermis in 3 of 12 non-neuropathic subjects, however, regenerating GAP-43+ endings were seen in dermis of almost all specimens. Lack of substance P+ nerve endings was characteristic for both groups. The reduced distribution of calcitonin gene-related peptide+ nerves in epidermis and dermis was seen mainly in neuropathic group. In neo-epidermis lack of nerve growth factor expression was observed in both groups, whereas neurotrophin 3 immunostaining was characteristic for neuropathic specimens (P < 0.03). Expression of trkA and trkC receptors did not differ significantly between groups. Low inflammatory cell infiltration and moderate presence of fibroblasts was characteristic for all studied specimens.

CONCLUSIONS

The observed reduction of foot skin innervation and neurogenic factors expression can be correlated with low inflammatory cell accumulation and subsequently leads to the observed chronicity of diabetic foot ulcer healing process in both neuropathic and non-neuropathic patients.

Opioids in pain management of blood-related malignancies

Opioids are basic analgesics used in the treatment of moderate to severe pain in patients affected by blood-related malignancies. They should be sequentially administered according to the World Health Organisation scale for cancer pain. Initial treatment and titration with opioids should be based on immediate-release preparations, to be administered at appropriate intervals in order to relieve pain and to satisfy the individual opioid requirement. Once a relatively good pain control has been achieved, a slow release formulation at equivalent doses can be given. Most patients can be adequately managed using oral formulation opioids. However, a small group, such as those presenting severe mucositis or requiring a rapid pain relief, should be managed by intravenous continuous infusion and/or by a patient-controlled analgesia system; while for patients in the community, there are distinct advantages to using the subcutaneous route. Other available routes of administration for opioids, can be used in selected circumstances, including rectal, transdermal, epidural, intrathecal and intramuscular. The invasive neuraxial route has a very limited role in patients with haematological malignancies, given the high risk of infection and bleeding. Through a close observation and a careful management, opioid-related side effects can be effectively prevented and treated. This article reviews the principles of opioid therapy and how opioids can be adapted for patients with pain due to haematological malignancies.