Karamarie Fecho

Catechol-O-methyltransferase inhibition increases pain sensitivity through activation of both β2- and β3-adrenergic receptors

Abstract Catechol‐O‐methyltransferase (COMT), an enzyme that metabolizes catecholamines, has recently been implicated in the modulation of pain. Our group demonstrated that human genetic variants of COMT are predictive for the development of Temporomandibular Joint Disorder (TMJD) and are associated with heightened experimental pain sensitivity [Diatchenko, L, Slade, GD, Nackley, AG, Bhalang, K, Sigurdsson, A, Belfer, I, et al., Genetic basis for individual variations in pain perception and the development of a chronic pain condition, Hum Mol Genet 2005;14:135–43.]. Variants associated with heightened pain sensitivity produce lower COMT activity. Here we report the mechanisms underlying COMT‐dependent pain sensitivity. To characterize the means whereby elevated catecholamine levels, resulting from reduced COMT activity, modulate heightened pain sensitivity, we administered a COMT inhibitor to rats and measured behavioral responsiveness to mechanical and thermal stimuli. We show that depressed COMT activity results in enhanced mechanical and thermal pain sensitivity. This phenomenon is completely blocked by the nonselective β‐adrenergic antagonist propranolol or by the combined administration of selective β2‐ and β3‐adrenergic antagonists, while administration of β1‐adrenergic, α‐adrenergic, or dopaminergic receptor antagonists fail to alter COMT‐dependent pain sensitivity. These data provide the first direct evidence that low COMT activity leads to increased pain sensitivity via a β2/3‐adrenergic mechanism. These findings are of considerable clinical importance, suggesting that pain conditions resulting from low COMT activity and/or elevated catecholamine levels can be treated with pharmacological agents that block both β2‐ and β3‐adrenergic receptors.

Fas ligand (gld)‐ and Fas (lpr)‐deficient mice do not show alterations in the extravasation or apoptosis of inflammatory neutrophils

Apoptosis of neutrophils plays a critical role in the resolution of acute inflammation. Neutrophils from human peripheral blood express Fas (CD95) and are sensitive to Fas ligand (FasL)/Fas‐mediated apoptosis. Mice carrying spontaneous mutations in the genes for fas ligand (B6/gld) or fas (B6/lpr) were used to assess the role of FasL/Fas in the kinetics and magnitude of neutrophil extravasation to the thioglycolate (TG)‐inflamed peritoneum and in the spontaneous apoptosis of TG‐elicited neutrophils. The results showed that TG‐elicited neutrophils (defined by flow cytometry as GR‐1/Ly‐6Ghi cells) from normal (B6) and B6/gld mice, but not from the Fas‐deficient B6/lpr mice, express high levels of Fas. The TG‐elicited neutrophil response began at 2 h, peaked at 4 h, and subsided by 24–48 h after TG administration in all three strains. However, the response was more prolonged in B6 mice, such that B6/gld and B6/lpr mice had fewer neutrophils at 6 h after TG administration than did B6 mice. Further studies showed that 4 h TG‐elicited neutrophils from B6, B6/gld and B6/lpr mice undergo apoptosis in vitro at similar rates (as assessed through flow cytometry by the decrease in forward angle light‐scatter and externalization of phosphatidylserine (PS; as detected by Annexin V‐FITC) that occur as neutrophils undergo apoptosis). Fas expression was down‐regulated on apoptotic neutrophils in conjunction with maximal PS externalization and decreased forward angle light‐scatter. Collectively, these findings suggest that FasL/Fas‐mediated apoptosis is not essential in regulating the lifespan of neutrophils during an acute inflammatory response. The abbreviated inflammatory response observed in FasL/Fas‐deficient mice is likely to be a secondary effect of the gld/lpr autoimmune/lymphoproliferative syndrome, and not a direct effect of FasL/Fas on the ability of inflammatory neutrophils to undergo apoptosis. J. Leukoc. Biol. 64: 373–383; 1998.

Postoperative mortality after inpatient surgery: Incidence and risk factors.

Purpose: This study determined the incidence of and identified risk factors for 48 hour (h) and 30 day (d) postoperative mortality after inpatient operations. Methods: A retrospective cohort study was conducted using Anesthesiology’s Quality Indicator database as the main data source. The database was queried for data related to the surgical procedure, anesthetic care, perioperative adverse events, and birth/death/operation dates. The 48 h and 30 d cumulative incidence of postoperative mortality was calculated and data were analyzed using Chi-square or Fisher’s exact test and generalized estimating equations. Results: The 48 h and 30 d incidence of postoperative mortality was 0.57% and 2.1%, respectively. Higher American Society of Anesthesiologists physical status scores, extremes of age, emergencies, perioperative adverse events and postoperative Intensive Care Unit admission were identified as risk factors. The use of monitored anesthesia care or general anesthesia versus regional or combined anesthesia was a risk factor for 30 d postoperative mortality only. Time under anesthesia care, perioperative hypothermia, trauma, deliberate hypotension and invasive monitoring via arterial, pulmonary artery or cardiovascular catheters were not identified as risk factors. Conclusions: Our findings can be used to track postoperative mortality rates and to test preventative interventions at our institution and elsewhere.

Evidence for the involvement of macrophage-derived nitric oxide in the modulation of immune status by a conditioned aversive stimulus

Prior work in our laboratory has demonstrated that exposure to a conditioned aversive stimulus developed through pairings with electric shock results in pronounced alterations of immune status. These conditioned alterations of immune status include a decreased in natural killer cell activity, decreased production of interleukin-2 and gamma-interferon by concanavalin A (ConA)-stimulated splenocytes and a profound suppression of the mitogenic responsiveness of T and B lymphocytes to mitogens. The present study examines the role of macrophage-derived nitric oxide in the conditioned stimulus-induced suppression of lymphocyte proliferation by measuring the level of nitrite accumulation in culture, determining the effect of macrophage depletion, and assessing the effect of NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of the L-arginine-dependent nitric-oxide synthesizing pathway, alone and in combination with L- or D-arginine. The results show that the conditioned suppression of the mitogenic responsiveness of splenocytes to ConA is accompanied by a marked increase in nitrite accumulation. Both the depletion of macrophages and the addition of L-NMMA attenuates the conditioned suppression of ConA-stimulated lymphocyte proliferation. Furthermore, the addition of excess L-arginine, but not D-arginine, counteracts the effect of L-NMMA. The present findings show that the neuroendocrine alterations induced by a conditioned aversive stimulus suppress lymphocyte proliferation through alteration of the production of nitric oxide by macrophages.

Basal and carrageenan-induced pain behavior in Sprague-Dawley, Lewis and Fischer rats.

Individual differences in pain sensitivity are believed to reflect the interplay of many factors, including genetics. Inbred rat strains can be used to study the impact of genetic factors on pain sensitivity. Inbred Lewis (LEW) and Fischer 344 (FIS) rat strains display profound and contrasting alterations in neuroendocrine, immunological and behavioral responses to stressors. Because of the established interactions between stressors, the neuroendocrine system, the immune system and pain processing pathways, we hypothesized that LEW and FIS rats would differ in their pain sensitivity. Pain sensitivity was assessed using several behavioral pain assays in untreated and carrageenan-inflamed LEW and FIS rats, and in the outbred Sprague-Dawley (SD) rat. The results showed that at baseline, FIS rats were the most sensitive to mechanical stimulation (the von Frey monofilament test) and the least sensitive to noxious heat pain (the Hargreaves radiant heat test). After intraplantar administration of carrageenan, LEW rats showed the least, and FIS rats showed the greatest, thermal hyperalgesia and mechanical allodynia/hyperalgesia. Hindlimb muscle grip force and tail-flick latencies did not differ across the three strains, either before or after carrageenan. These results demonstrate differences in basal and carrageenan-induced pain sensitivity in LEW, FIS and SD rats, which extend earlier findings that genetic factors modulate both basal and inflammatory pain. The results further demonstrate that basal pain sensitivity can be predictive of inflammatory pain sensitivity, with the direction of the effect dependent upon the pain measure.

Phenotypic and functional assessments of immune status in the rat spleen following acute heroin treatment.

Heroin use is associated with an increased incidence of several types of infections, including HIV. Yet few studies have assessed whether heroin produces pharmacological alterations of immune status that might contribute to the increased rate of infections amongst heroin users. The present study investigated whether a single administration of heroin to rats produces dose-dependent alterations in functional measures of immune status and in the distribution of leukocyte subsets in the spleen. The results showed that heroin produces a dose-dependent, naltrexone-reversible suppression of the concanavalin A-stimulated proliferation of T cells, lipopolysaccharide-stimulated proliferation of B cells, production of interferon-gamma and cytotoxicity of natural killer (NK) cells in the spleen. Heroins suppressive effect on NK cell activity results in part from a heroin-induced decrease in the relative number of NKR-P1A(hi) CD3- NK cells in the spleen. Heroin also decreases the percent of a splenic granulocyte subset, the CD11b/c+ HIS48(hi) cells, whose function currently is unknown. In contrast, heroin does not alter relative numbers of CD4+ CD3+ T cells, CD8+ CD3+ T cells, CD45+ B cells, NKR-P1A(lo) CD3+ T cells, CD11b/c+ ED1+ (or CD11b/c+ HIS48-) monocytes/macrophages or CD11b/c+ ED1- (or CD11b/c+ HIS48+) total granulocytes in the spleen. Collectively, these findings demonstrate that heroin produces pharmacological effects on functional and phenotypic measures of immune status.

In-hospital resuscitation: opioids and other factors influencing survival

Purpose: “Code Blue” is a standard term used to alertt hospital staff that a patient requires resuscitation. This study determined rates of survival from Code Blue events and the role of opioids and other factors on survival. Methods: Data derived from medical records and the Code Blue and Pharmacy databases were analyzed for factors affecting survival. Results: During 2006, rates of survival from the code only and to discharge were 25.9% and 26.4%, respectively, for Code Blue events involving cardiopulmonary resuscitation (CPR; N = 216). Survival rates for events not ultimately requiring CPR (N = 77) were higher, with 32.5% surviving the code only and 62.3% surviving to discharge. For CPR events, rates of survival to discharge correlated inversely with time to chest compressions and defibrillation, precipitating event, need for airway management, location and age. Time of week, witnessing, postoperative status, gender and opioid use did not influence survival rates. For non-CPR events, opioid use was associated with decreased survival. Survival rates were lowest for patients receiving continuous infusions (P < 0.01) or iv boluses of opioids (P < 0.05). Conclusions: One-quarter of patients survive to discharge after a CPR Code Blue event and two-thirds survive to discharge after a non-CPR event. Opioids may influence survival from non-CPR events.

Effects of carrageenan and morphine on acute inflammation and pain in Lewis and Fischer rats.

The present study used inbred, histocompatible Fischer 344 (FIS) and Lewis (LEW) rats to begin to explore the role of the hypothalamic-pituitary-adrenal (HPA) axis in the immune processes and pain behavior associated with the carrageenan model of acute hindpaw inflammation. Because the HPA axis contributes in part to morphines analgesic and immunomodulatory properties, the present study also assessed the effects of morphine in carrageenan-inflamed LEW and FIS rats. The results showed that carrageenan-induced hindpaw swelling and pain behavior were greater in FIS than in LEW rats. The enhanced hindpaw swelling in FIS rats correlated with an increase in myeloperoxidase (MPO; a measure of neutrophils) in the inflamed hindpaw. FIS rats showed lower circulating levels of TNFalpha, higher IL-6 levels, and similar IL-1beta and nitric oxide levels, when compared to LEW rats. Morphine produced a significant decrease in carrageenan-induced hindpaw swelling and MPO in both strains, but morphine did not significantly alter circulating cytokine/mediator levels. Morphines analgesic effects were greater in the inflamed than the noninflamed hindpaw, and they did not correlate with morphines anti-inflammatory effects. In fact, low doses of morphine produced a mechanical allodynia and hyperalgesia in the noninflamed hindpaw of FIS, but not LEW, rats. These results suggest a positive relationship between HPA axis activity and acute inflammation and inflammatory pain. In contrast, little evidence is provided for HPA axis involvement in morphines anti-inflammatory or analgesic effects.

Anesthesia and Analgesia–Related Preferences and Outcomes of Women Who Have Birth Plans

INTRODUCTION This study described anesthesia and analgesia-related preferences and outcomes of women who used a birth plan for labor and birth. METHODS A prospective cohort study was conducted (N = 63). Data were abstracted from medical records, birth plans, and a follow-up survey. Descriptive statistics were used for analysis. RESULTS Women who elected birth plans were primarily white, college-educated, primigravida, and under the care of a certified nurse-midwife. One-third of births were induced, 10% required instrumentation, and 29% were cesarean births. Nearly every birth was associated with at least 1 labor and birth complication, although most complications were minor. Analgesic preferences were reported to be the most important birth plan request. Greater than 50% of women requested to avoid epidural analgesia; however, 65% of women received epidural analgesia. On follow-up, greater than 90% of women who received epidural analgesia reported being pleased. The majority of women agreed that the birth plan enhanced their birth experiences, added control, clarified their thoughts, and improved communication with their health care providers. DISCUSSION Anesthesia and analgesia-related preferences were an important component of the birth plans. The majority of women favorably viewed the use of a birth plan, whether or not preferences were fulfilled or complications occurred.

Evidence for the Involvement of Macrophage-Derived Nitric Oxide in the Immunomodulatory Effect of Morphine and Aversive Pavlovian Conditioning

It is well established that in vivo administration of morphine to rats produces alterations in several in vitro measures of immune status. For example, our work has shown that the administration of morphine to Lewis rats induces a dose-dependent reduction in the proliferative response of splenic and blood lymphocytes, a reduction in the production of interleukin-2 and γ-interferon, and a reduction in the cytotoxic response of natural killer cells. Furthermore, we have shown that administration of the opioid antagonist, naltrexone, dose-dependently antagonizes the immunomodulatory effects of morphine, indicating that the immunomodulatory effects of morphine are mediated by activity at opioid receptors1.