Comparison of bupivacaine liposome injectable solution and fentanyl for postoperative analgesia in dogs undergoing limb amputation.

OBJECTIVE: The objectives of the study were to compare the clinical efficacy and adverse effects of two analgesic protocols consisting of bupivacaine liposome injectable solution (BLIS) and 0.5% bupivacaine and fentanyl for postsurgical analgesia in dogs undergoing limb amputation. STUDY DESIGN: Randomized, double-blind, prospective, controlled, intent-to-treat, clinical noninferiority trial. ANIMALS: Forty client-owned dogs. METHODS: Dogs undergoing amputation were randomly assigned to either the BLIS or control group. Postoperative pain, sedation, nausea, and amount eaten were assessed using appropriate scales at 6, 12, 18, and 24 h by trained individuals blinded to the treatment protocol. Rescue analgesia was provided for Glasgow composite measure pain scale (short form) (CMPS-SF) scores of 5 or above. Clients were requested to pain score their dogs at home using a visual analogue scale (VAS) for 48 h following discharge. RESULTS: Forty dogs completed this study (20 control dogs and 20 BLIS dogs). The BLIS and control groups were equivalent for sedation, nausea, amount eaten, and pain, at all time periods except at 6 h (p < .01), when the BLIS group pain score was lower. CONCLUSION: The BLIS provided equivalent analgesia with fewer adverse effects than fentanyl constant rate infusion (CRI) following limb amputation. Rescue analgesia was provided to five dogs in the BLIS group and four in the control group, and there was no statistical difference. Nausea scores did not differ statistically. CLINICAL SIGNIFICANCE: As BLIS provides equivalent analgesia, this may allow for decreased reliance on opioids in the immediate postoperative period.

A TLR7/8 agonist increases efficacy of anti-fentanyl vaccines in rodent and porcine models.

Opioid use disorders (OUD) and overdose are public health threats worldwide. Widespread access to highly potent illicit synthetic opioids such as fentanyl is driving the recent rise in fatal overdoses. Vaccines containing fentanyl-based haptens conjugated to immunogenic carrier proteins offer a long-lasting, safe, and cost-effective strategy to protect individuals from overdose upon accidental or deliberate exposure to fentanyl and its analogs. Prophylactic or therapeutic active immunization with an anti-fentanyl vaccine induces the production of fentanyl-specific antibodies that bind the drug in the blood and prevent its distribution to the brain, which reduces its reinforcing effects and attenuates respiratory depression and bradycardia. To increase the efficacy of a lead anti-fentanyl vaccine, this study tested whether the incorporation of synthetic toll-like receptor (TLR) 4 and TLR7/8 agonists as vaccine adjuvants would increase vaccine efficacy against fentanyl challenge, overdose, and self-administration in either rats or Hanford miniature pigs. Formulation of the vaccine with a nucleolipid TLR7/8 agonist enhanced its immunogenicity and efficacy in preventing fentanyl-induced respiratory depression, analgesia, bradycardia, and self-administration in either rats or mini-pigs. These studies support the use of TLR7/8 adjuvants in vaccine formulations to improve their clinical efficacy against OUD and potentially other substance use disorders (SUD).

Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses.

Lower than expected arterial oxygen tension (PaO2) continues to be an unresolved problem in equine anesthesia. The aim of this randomized, crossover, and prospective study using six adult horses is to determine if a 15° reverse Trendelenburg position (RTP) increases PaO2 during inhalation anesthesia. Under constant-dose isoflurane anesthesia, dorsally recumbent horses were positioned either horizontally (HP) or in a 15° RTP for 2 h. Lungs were mechanically ventilated (15 mL/kg, 6 breaths/min). Arterial carbon dioxide tension (PaCO2), PaO2, inspired oxygen fraction (FiO2), and end-tidal carbon dioxide tension (EtCO2) were determined every 30 min during anesthesia. Indices of dead-space ventilation (Vd/Vt), oxygenation (P-F ratio), and perfusion (F-shunt) were calculated. Dobutamine and phenylephrine were used to support mean arterial pressure (MAP). Data are presented as median and range. In one horse, which was deemed an outlier due to its thoracic dimensions and body conformation, indices of oxygenation worsened in RTP compared to HP (median PaO2 438 vs. 568 mmHg; P-F ratio 454 vs. 586 mmHg, and F-shunt 13.0 vs. 5.7 mmHg). This horse was excluded from calculations. In the remaining five horses they were significantly better with RTP compared to HP. Results in remaining five horses showed that PaO2 (502, 467-575 vs. 437, 395-445 mmHg), P-F ratio (518, 484-598 vs. 455, 407-458 mmHg), and F-shunt (10.1, 4.2-11.7 vs. 14.2, 13.8-16.0 mmHg) were significantly different between RTP and HP (p = 0.03). Other variables were not significantly different. In conclusion, the 15° RTP resulted in better oxygenation than HP in dorsally recumbent, isoflurane-anesthetized horses, although worsening of oxygenation may occur in individual horses. A study detailing the cardiovascular consequences of RTP is necessary before it can be recommended for clinical practice.

CD38 plays an age-related role in cholinergic deregulation of airway smooth muscle contractility.

BACKGROUND: Allergen-induced airway hyperresponsiveness in neonatal mice, but not adult mice, is caused by elevated innervation and consequent cholinergic hyperstimulation of airway smooth muscle (ASM). Whether this inflammation-independent mechanism contributes to ASM hypercontraction in childhood asthma warrants investigation. OBJECTIVE: We aimed to establish the functional connection between cholinergic stimulation and ASM contractility in different human age groups. METHODS: First, we used a neonatal mouse model of asthma to identify age-related mediators of cholinergic deregulation of ASM contractility. Next, we conducted validation and mechanistic studies in primary human ASM cells and precision-cut lung slices from young (<5 years old) and adult (>20 years old) donor lungs. Finally, we evaluated the therapeutic potential of the identified cholinergic signaling mediators using culture models of human ASM hypercontraction. RESULTS: ASM hypercontraction due to cholinergic deregulation in early postnatal life requires CD38. Mechanistically, cholinergic signaling activates the phosphatidylinositol 3-kinase/protein kinase B pathway in immature ASM cells to upregulate CD38 levels, thereby augmenting the Ca2+ response to contractile agonists. Strikingly, this early-life, CD38-mediated ASM hypercontraction is not alleviated by the ß-agonist formoterol. CONCLUSIONS: The acetylcholine-phosphatidylinositol 3-kinase/protein kinase B-CD38 axis is a critical mechanism of airway hyperresponsiveness in early postnatal life. Targeting this axis may provide a tailored treatment for children at high risk for allergic asthma.

Targeting Soluble Epoxide Hydrolase and Cyclooxygenases Enhance Joint Pain Control, Stimulate Collagen Synthesis, and Protect Chondrocytes From Cytokine-Induced Apoptosis.

Objective: To determine the symptomatic and disease-modifying capabilities of sEH and COX inhibitors during joint inflammation. Methods: Using a blinded, randomized, crossover experimental design, 6 adult healthy horses were injected with lipopolysaccharide (LPS; 3 µg) from E. coli in a radiocarpal joint and concurrently received the non-selective cyclooxygenase (COX) inhibitor phenylbutazone (2 mg/kg), the sEH inhibitor t-TUCB (1 mg/kg) or both (2 mg/kg phenylbutazone and 0.1, 0.3, and 1 mg/kg t-TUCB) intravenously. There were at least 30 days washout between treatments. Joint pain (assessed via inertial sensors and peak vertical forces), synovial fluid concentrations of prostanoids (PGE2, TxB2), cytokines (IL-1ß, IL-6, TNF-α) and biomarkers of collagen synthesis (CPII) and degradation (C2C) were measured at pre-determined intervals over a 48-h period. The anti-apoptotic effect of COX and sEH inhibitors was determined via ELISA technique in primary equine chondrocytes incubated with TNF-α (10 ng/ml) for 24 h. Apoptosis was also determined in chondrocytes incubated with sEH-generated metabolites. Results: Combined COX and sEH inhibition produced significantly better control of joint pain, prostanoid responses, and collagen synthesis-degradation balance compared to each compound separately. When administered separately, pain control was superior with COX vs. sEH inhibition. Cytokine responses were not different during COX and/or sEH inhibition. In cultured chondrocytes, sEH inhibition alone or combined with COX inhibition, but not COX inhibition alone had significant anti-apoptotic effects. However, sEH-generated metabolites caused concentration-dependent apoptosis. Conclusions: Combined COX and sEH inhibition optimize pain control, attenuate loss of articular cartilage matrix during joint inflammation and cytokine-induced chondrocyte apoptosis.

Assessment of the effects of gabapentin on activity levels and owner-perceived mobility impairment and quality of life in osteoarthritic geriatric cats.

OBJECTIVE Toevaluate effects of gabapentin on activity levels and owner-perceived mobility impairment and quality of life (QOL) in osteoarthritic geriatric cats. DESIGN Blinded, placebo-controlled, randomized crossover-design study. ANIMALS 20 osteoarthritic cats (≥ 10 years old). PROCEDURES Cats received gabapentin (10 mg/kg [4.5 mg/lb]) or placebo treatment, PO, every 12 hours for 2 weeks, followed by the alternate treatment (with no washout period). Activity was assessed with a collar-mounted accelerometer. A client-specific outcome measure (CSOM) questionnaire was used weekly to collect owner assessments of 3 selected activities in which their cats had impaired mobility; QOL ratings (worse, the same, or improved) following crossover to each treatment and for the overall study period were collected at the end of the investigation. Activity counts, CSOM and QOL data, and deterioration in impaired activities (ie, decrease of ≥ 2 points in CSOM scores) associated with treatment crossover were assessed statistically. Adverse events were recorded. RESULTS Gabapentin administration was associated with significantly lower mean daily activity counts (48,333 vs 39,038 counts/d) and significantly greater odds (approx 3-fold change) of CSOM ratings indicating improvement in impaired activities, compared with results for the placebo treatment. A greater proportion of cats had deterioration in impaired activities after the crossover from gabapentin to placebo than when the opposite occurred, but the proportion of cats with worsened QOL did not differ between sequences. Adverse events were noted for 10 cats (9 that completed the study) during gabapentin treatment (sedation, ataxia, weakness, and muscle tremors) and 1 cat during placebo treatment (lethargy). CONCLUSIONS AND CLINICAL RELEVANCE Gabapentin treatment was associated with improvement in owner-identified impaired activities of osteoarthritic cats. Activity levels were lower than those during placebo treatment, and sedation was the most common adverse effect.

CD38/cADPR Signaling Pathway in Airway Disease: Regulatory Mechanisms.

Asthma is an inflammatory disease in which proinflammatory cytokines have a role in inducing abnormalities of airway smooth muscle function and in the development of airway hyperresponsiveness. Inflammatory cytokines alter calcium (Ca2+) signaling and contractility of airway smooth muscle, which results in nonspecific airway hyperresponsiveness to agonists. In this context, Ca2+ regulatory mechanisms in airway smooth muscle and changes in these regulatory mechanisms encompass a major component of airway hyperresponsiveness. Although dynamic Ca2+ regulation is complex, phospholipase C/inositol tris-phosphate (PLC/IP3) and CD38-cyclic ADP-ribose (CD38/cADPR) are two major pathways mediating agonist-induced Ca2+ regulation in airway smooth muscle. Altered CD38 expression or enhanced cyclic ADP-ribosyl cyclase activity associated with CD38 contributes to human pathologies such as asthma, neoplasia, and neuroimmune diseases. This review is focused on investigations on the role of CD38-cyclic ADP-ribose signaling in airway smooth muscle in the context of transcriptional and posttranscriptional regulation of CD38 expression. The specific roles of transcription factors NF-kB and AP-1 in the transcriptional regulation of CD38 expression and of miRNAs miR-140-3p and miR-708 in the posttranscriptional regulation and the underlying mechanisms of such regulation are discussed.

Evaluation of tramadol for treatment of osteoarthritis in geriatric cats.

OBJECTIVE To evaluate tramadol for treatment of signs of pain and impaired mobility in geriatric cats with osteoarthritis. DESIGN Randomized controlled crossover trial. ANIMALS 24 client-owned geriatric (≥ 10 years old) cats with osteoarthritis. PROCEDURES Otherwise healthy cats with owner-identified mobility impairment and clinical and radiographic evidence of osteoarthritis involving at least 1 appendicular joint were enrolled in the study. Cats were treated with tramadol orally at dosages of 0 (placebo), 1, 2, and 4 mg/kg (0, 0.45, 0.9, and 1.8 mg/lb) twice a day for 5 days, with a 2-day (weekend) washout period between treatments. Mobility was assessed with a collar-mounted activity monitor system, and impairments in activity were assessed with a client-completed questionnaire. RESULTS 17 cats completed the study; 7 cats were withdrawn. There was a significant increase in activity with the 2-mg/kg dosage of tramadol, compared with activity when cats received the placebo. Significantly more owners (11/18) considered their cats to have improved with the 2-mg/kg treatment, compared with all other dosages (6/19 to 8/21). Most owners (17/20 [85%]) considered their cat's global quality of life to have improved during the study. Adverse events, predominantly euphoria, dysphoria, sedation, decreased appetite, and diarrhea, were significantly more frequent with the 4-mg/kg (8/19) and 2-mg/kg (6/18) treatments but not with the 1-mg/kg (2/21) treatment, compared with frequency of adverse events with the placebo (0/21). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested a beneficial effect of twice-daily oral administration of tramadol at a dosage of 2 mg/kg in geriatric cats with osteoarthritis. Adverse events were dose dependent, and caution should be exercised in cats that have concurrent disease or are receiving other drugs that may produce adverse gastrointestinal effects.

Comparison between the effects of postanesthetic xylazine and dexmedetomidine on characteristics of recovery from sevoflurane anesthesia in horses.

OBJECTIVE: To compare postanesthetic xylazine and dexmedetomidine on recovery characteristics from sevoflurane anesthesia in horses. STUDY DESIGN: Randomized, crossover study. ANIMALS: Six geldings, mean±standard deviation (SD) (range), 17±4 (11-24) years and 527±80 (420-660) kg. METHODS: Horses were anesthetized with sevoflurane for 60 minutes under standardized conditions for a regional limb perfusion study. In recovery, horses were administered either xylazine (200 µg kg-1) or dexmedetomidine (0.875 µg kg-1) intravenously. Recoveries were unassisted and were video-recorded for later evaluation of recovery events and quality by two individuals unaware of treatment allocation. Recovery quality was assessed using a 100 mm visual analog scale (VAS) (0=poor recovery, 100=excellent recovery), the Edinburgh Scoring System (ESS) (0-100; 100=excellent recovery) and the mean attempt interval (MAI) (longer=better). Data are mean±SD. RESULTS: All recovery quality assessments (xylazine and dexmedetomidine, respectively: VAS: 71±21 mm, 84±13 mm; ESS: 65±22, 67±30; MAI: 52±24 minutes, 60±32 minutes) and events (first limb movement: 37±8 minutes, 42±10 minutes; first attempt to lift head: 44±12 minutes, 48±9 minutes; first attempt to sternal posture: 57±28 minutes, 50±7 minutes; number of head bangs: 2.0±3.0, 0.5±0.5; time to first attempt to stand: 72±6 minutes, 78±13 minutes; time to standing: 79±14 minutes, 84±13 minutes) did not differ significantly between treatments (p>0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Recovery characteristics did not differ significantly between postanesthetic xylazine and dexmedetomidine following 1 hour of sevoflurane anesthesia in horses in this study. Further evaluations in more horses and in younger horses are required to confirm these results.

CD38 in the pathogenesis of allergic airway disease: Potential therapeutic targets.

CD38 is an ectoenzyme that catalyzes the conversion of ß-nicotinamide adenine dinucleotide (ß-NAD) to cyclic adenosine diphosphoribose (cADPR) and adenosine diphosphoribose (ADPR) and NADP to nicotinic acid adenine dinucleotide phosphate (NAADP) and adenosine diphosphoribose-2'-phosphate (ADPR-P). The metabolites of NAD and NADP have roles in calcium signaling in different cell types including airway smooth muscle (ASM) cells. In ASM cells, inflammatory cytokines augment CD38 expression and to a greater magnitude in cells from asthmatics, indicating a greater capacity for the generation of cADPR and ADPR in ASM from asthmatics. CD38 deficient mice develop attenuated airway responsiveness to inhaled methacholine following allergen sensitization and challenge compared to wild-type mice indicating its potential role in asthma. Regulation of CD38 expression in ASM cells is achieved by mitogen activated protein kinases, specific isoforms of PI3 kinases, the transcription factors NF-κB and AP-1, and post-transcriptionally by microRNAs. This review will focus on the role of CD38 in intracellular calcium regulation in ASM, contribution to airway inflammation and airway hyperresponsiveness in mouse models of allergic airway inflammation, the transcriptional and post-transcriptional mechanisms of regulation of expression, and outline approaches to inhibit its expression and activity.

Desflurane and sevoflurane elimination kinetics and recovery quality in horses.

OBJECTIVE: To evaluate pharmacokinetics, recovery times, and recovery quality in horses anesthetized with 1.2 times the minimum alveolar concentration of sevoflurane or desflurane. ANIMALS: 6 healthy adult horses. PROCEDURES: Anesthesia was maintained with sevoflurane or desflurane for 2 hours at 1.2 times the minimum alveolar concentration. Horses recovered without assistance. During recovery, end-tidal gas samples were collected until horses spontaneously moved. Anesthetic concentrations were measured by use of gas chromatography. After a 1-week washout period, horses were anesthetized with the other inhalation agent. Video recordings of anesthetic recovery were evaluated for recovery quality on the basis of a visual analogue scale by investigators who were unaware of the anesthetic administered. Anesthetic washout curves were fit to a 2-compartment kinetic model with multivariate nonlinear regression. Normally distributed interval data were analyzed by means of paired Student t tests; ordinal or nonnormally distributed data were analyzed by means of Wilcoxon signed rank tests. RESULTS: Horses recovered from both anesthetics without major injuries. Results for subjective recovery evaluations did not differ between anesthetics. Area under the elimination curve was significantly smaller and time to standing recovery was significantly less for desflurane than for sevoflurane, although distribution and elimination constants did not differ significantly between anesthetics. CONCLUSIONS AND CLINICAL RELEVANCE: Differences in area under elimination the curve between anesthetics indicated more rapid clearance for desflurane than for sevoflurane in horses, as predicted by anesthetic blood solubility differences in this species. More rapid elimination kinetics was associated with faster recovery times, but no association with improved subjective recovery quality was detected.

CD38 and airway hyper-responsiveness: studies on human airway smooth muscle cells and mouse models.

Asthma is an inflammatory disease in which altered calcium regulation, contractility, and airway smooth muscle (ASM) proliferation contribute to airway hyper-responsiveness and airway wall remodeling. The enzymatic activity of CD38, a cell-surface protein expressed in human ASM cells, generates calcium mobilizing second messenger molecules such as cyclic ADP-ribose. CD38 expression in human ASM cells is augmented by cytokines (e.g., TNF-α) that requires the activation of MAP kinases and the transcription factors, NF-κB and AP-1, and is post-transcriptionally regulated by miR-140-3p and miR-708 by binding to 3' Untranslated Region of CD38 as well as by modulating the activation of signaling mechanisms involved in its regulation. Mice deficient in Cd38 exhibit reduced airway responsiveness to inhaled methacholine relative to the response in wild-type mice. Intranasal challenge of Cd38-deficient mice with TNF-α or IL-13, or the environmental fungus Alternaria alternata, causes significantly attenuated methacholine responsiveness compared with wild-type mice, with comparable airway inflammation. Reciprocal bone marrow transfer studies revealed partial restoration of airway hyper-responsiveness to inhaled methacholine in the Cd38-deficient mice. These studies provide evidence for CD38 involvement in the development of airway hyper-responsiveness; a hallmark feature of asthma. Future studies aimed at drug discovery and delivery targeting CD38 expression and (or) activity are warranted.

Airway responsiveness in CD38-deficient mice in allergic airway disease: studies with bone marrow chimeras.

CD38 is a cell-surface protein involved in calcium signaling and contractility of airway smooth muscle. It has a role in normal airway responsiveness and in airway hyperresponsiveness (AHR) developed following airway exposure to IL-13 and TNF-α but appears not to be critical to airway inflammation in response to the cytokines. CD38 is also involved in T cell-mediated immune response to protein antigens. In this study, we assessed the contribution of CD38 to AHR and inflammation to two distinct allergens, ovalbumin and the epidemiologically relevant environmental fungus Alternaria. We also generated bone marrow chimeras to assess whether Cd38(+/+) inflammatory cells would restore AHR in the CD38-deficient (Cd38(-/-)) hosts following ovalbumin challenge. Results show that wild-type (WT) mice develop greater AHR to inhaled methacholine than Cd38(-/-) mice following challenge with either allergen, with comparable airway inflammation. Reciprocal bone marrow transfers did not change the native airway phenotypic differences between WT and Cd38(-/-) mice, indicating that the lower airway reactivity of Cd38(-/-) mice stems from Cd38(-/-) lung parenchymal cells. Following bone marrow transfer from either source and ovalbumin challenge, the phenotype of Cd38(-/-) hosts was partially reversed, whereas the airway phenotype of the WT hosts was preserved. Airway inflammation was similar in Cd38(-/-) and WT chimeras. These results indicate that loss of CD38 on hematopoietic cells is not sufficient to prevent AHR and that the magnitude of airway inflammation is not the predominant underlying determinant of AHR in mice.

Effects of pre-operative administration of medetomidine on plasma insulin and glucose concentrations in healthy dogs and dogs with insulinoma.

OBJECTIVE: To investigate the effect of medetomidine on plasma glucose and insulin concentrations in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery. ANIMALS: Twenty-five dogs with insulinoma and 26 healthy dogs. METHODS: In dogs with insulinoma, medetomidine (5 µg kg(-1) ) was randomly included (n = 12) or omitted (n = 13) from the pre-anesthetic medication protocol, which typically contained an opioid and an anticholinergic. Healthy dogs received medetomidine (5 µg kg(-1) ; n = 13) or acepromazine (0.04 mg kg(-1) ; n = 13) plus an opioid (morphine 0.5 mg kg(-1) ) and an anticholinergic (atropine 0.04 mg kg(-1) ) as pre-anesthetic medications. Pre-anesthetic medications were given intramuscularly. Plasma glucose and insulin concentrations were measured before (sample 1) and 30 minutes after pre-anesthetic medication (sample 2), and at the end of surgery in dogs with insulinoma or at 2 hours of anesthesia in healthy dogs (sample 3). Glucose requirement to maintain intra-operative normoglycemia in dogs with insulinoma was quantified and compared. Data were analyzed with anova and Bonferroni post-test, t-tests or chi-square tests as appropriate with p < 0.05 considered significant. Data are shown as mean ± SD. RESULTS: Medetomidine significantly decreased plasma insulin concentrations and increased plasma glucose concentrations in healthy dogs and those with insulinoma. These variables did not change significantly in the dogs not receiving medetomidine. In the dogs with insulinoma, intra-operative glucose administration rate was significantly less in the animals that received medetomidine compared to those that did not. CONCLUSIONS: Pre-anesthetic administration of medetomidine significantly suppressed insulin secretion and increased plasma glucose concentration in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery. CLINICAL RELEVANCE: These findings support the judicious use of medetomidine at low doses as an adjunct to the anesthetic management of dogs with insulinoma.

Potential role of the CD38/cADPR signaling pathway as an underlying mechanism of the effects of medetomidine on insulin and glucose homeostasis.

OBJECTIVE: To investigate the CD38/cADPR signaling pathway as possible underlying mechanism of the effects of medetomidine on insulin and glucose homeostasis. ANIMALS: Thirty-two C57BL/6 mice of both sexes. METHODS: Wild-type (WT) and CD38-knockout (CD38(-/-) ) mice received medetomidine (50 µg kg(-1) ) or a similar volume of 0.9% NaCl (control) by intraperitoneal (IP) injection (each group n = 8). The mice were euthanized 45 minutes later with sodium pentobarbital IP and blood was sampled via cardiac puncture. Insulin and glucose concentrations were measured by radioimmunoassay and by the oxygen rate method, respectively. Data were analyzed with anova and Bonferroni post hoc (5% significance) and are shown as mean ± SD. RESULTS: Plasma insulin and glucose concentrations were similar between WT and CD38(-/-) mice under control conditions. As compared to controls, medetomidine administration produced a statistically significant decrease in plasma insulin concentrations in the WT mice whereas the decrease in the CD38(-/-) mice was not statistically significant. Correspondingly, medetomidine caused a significantly greater increase in plasma glucose concentrations in the WT than in the CD38(-/-) mice. CONCLUSION: The CD38/cADPR signaling pathway may be one underlying mechanism of the glucose and insulin effects of the alpha-2 adrenergic receptor agonist medetomidine and likely other drugs of its class.

Use of a soluble epoxide hydrolase inhibitor as an adjunctive analgesic in a horse with laminitis.

HISTORY: A 4-year old, 500 kg Thoroughbred female horse diagnosed with bilateral forelimb laminitis and cellulitis on the left forelimb became severely painful and refractory to non-steroidal anti-inflammatory therapy (flunixin meglumine on days 1, 2, 3 and 4; and phenylbutazone on days 5, 6 and 7) alone or in combination with gabapentin (days 6 and 7). PHYSICAL EXAMINATION: Pain scores assessed independently by three individuals with a visual analog scale (VAS; 0 = no pain and 10 = worst possible pain) were 8.5 on day 6, and it increased to 9.5 on day 7. Non-invasive blood pressure monitoring revealed severe hypertension. MANAGEMENT: As euthanasia was being considered for humane reasons, a decision was made to add an experimental new drug, trans-4-{4-[3-(4-Trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid (t-TUCB), which is a soluble epoxide hydrolase (sEH) inhibitor, to the treatment protocol. Dose and frequency of administration were selected based on the drug potency against equine sEH to produce plasma concentrations within the range of 30 nmol L(-1) and 2.5 µmol L(-1) . Pain scores decreased sharply and remarkably following t-TUCB administration and blood pressure progressively decreased to physiologic normal values. Plasma concentrations of t-TUCB, measured daily, were within the expected range, whereas phenylbutazone and gabapentin plasma levels were below the suggested efficacious concentrations. FOLLOW UP: No adverse effects were detected on clinical and laboratory examinations during and after t-TUCB administration. No new episodes of laminitis have been noted up to the time of writing (120 days following treatment). CONCLUSIONS: Inhibition of sEH with t-TUCB was associated with a significant improvement in pain scores in one horse with laminitis whose pain was refractory to the standard of care therapy. No adverse effects were noticed. Future studies evaluating the analgesic and protective effects of these compounds in painful inflammatory diseases in animals are warranted.

Effect of ketamine hydrochloride on the analgesic effects of tramadol hydrochloride in horses with signs of chronic laminitis-associated pain.

OBJECTIVE: To investigate the effects of ketamine hydrochloride on the analgesic effects of tramadol hydrochloride in horses with signs of pain associated with naturally occurring chronic laminitis. ANIMALS: 15 client-owned adult horses with chronic laminitis. PROCEDURES: Each horse received tramadol alone or tramadol and ketamine in a randomized, crossover study (≥ 2 months between treatments). Tramadol (5 mg/kg) was administered orally every 12 hours for 1 week. When appropriate, ketamine (0.6 mg/kg/h) was administered IV for 6 hours on each of the first 3 days of tramadol administration. Noninvasive systemic blood pressure values, heart and respiratory rates, intestinal sounds, forelimb load and off-loading frequency (determined via force plate system), and plasma tumor necrosis factor-α and thromboxane B(2) concentrations were assessed before (baseline) during (7 days) and after (3 days) each treatment. RESULTS: Compared with baseline data, arterial blood pressure decreased significantly both during and after tramadol-ketamine treatment but not with tramadol alone. Forelimb off-loading frequency significantly decreased during the first 3 days of treatment with tramadol only, returning to baseline frequency thereafter. The addition of ketamine to tramadol treatment reduced off-loading frequency both during and after treatment. Forelimb load did not change with tramadol alone but increased with tramadol-ketamine treatment. Plasma concentrations of tumor necrosis factor-α and thromboxane B(2) were significantly reduced with tramadol-ketamine treatment but not with tramadol alone. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with chronic laminitis, tramadol administration induced limited analgesia, but this effect was significantly enhanced by administration of subanesthetic doses of ketamine.

Role of CD38 in TNF-alpha-induced airway hyperresponsiveness.

CD38 is involved in normal airway function, IL-13-induced airway hyperresponsiveness (AHR), and is also regulated by tumor necrosis factor (TNF)-alpha in airway smooth muscle (ASM) cells. This study aimed to determine whether TNF-alpha-induced CD38 upregulation in ASM cells contributes to AHR, a hallmark of asthma. We hypothesized that AHR would be attenuated in TNF-alpha-exposed CD38-deficient (CD38KO) mice compared with wild-type (WT) controls. Mice (n = 6-8/group) were intranasally challenged with vehicle control or TNF-alpha (50 ng) once and every other day during 1 or 4 wk. Lung inflammation and AHR, measured by changes in lung resistance after inhaled methacholine, were assessed 24 h following the last challenge. Tracheal rings were incubated with TNF-alpha (50 ng/ml) to assess contractile changes in the ASM. While a single TNF-alpha challenge caused no airway inflammation, both multiple-challenge protocols induced equally significant inflammation in CD38KO and WT mice. A single intranasal TNF-alpha challenge induced AHR in the WT but not in the CD38KO mice, whereas both mice developed AHR after 1 wk of challenges. The AHR was suppressed by extending the challenges for 4 wk in both mice, although to a larger magnitude in the WT than in the CD38KO mice. TNF-alpha increased ASM contractile properties in tracheal rings from WT but not from CD38KO mice. In conclusion, CD38 contributes to TNF-alpha-induced AHR after a brief airway exposure to the cytokine, likely by mediating changes in ASM contractile responses, and is associated with greater AHR remission following chronic airway exposure to TNF-alpha. The mechanisms involved in this remission remain to be determined.

CD38-deficient mice have reduced airway hyperresponsiveness following IL-13 challenge.

The transmembrane glycoprotein CD38 in airway smooth muscle is the source of cyclic-ADP ribose, an intracellular calcium-releasing molecule, and is subject to regulatory effects of cytokines such as interleukin (IL)-13, a cytokine implicated in asthma. We investigated the role of CD38 in airway hyperresponsiveness using a mouse model of IL-13-induced airway disease. Wild-type (WT) and CD38-deficient (CD38KO) mice were intranasally challenged with 5 microg of IL-13 three times on alternate days under isoflurane anesthesia. Lung resistance (R(L)) in response to inhaled methacholine was measured 24 h after the last challenge in pentobarbital-anesthetized, tracheostomized, and mechanically ventilated mice. Bronchoalveolar cytokines, bronchoalveolar and parenchymal inflammation, and smooth muscle contractility and relaxation using tracheal segments were also evaluated. Changes in methacholine-induced R(L) were significantly greater in the WT than in the CD38KO mice following intranasal IL-13 challenges. Airway reactivity after IL-13 exposure, as measured by the slope of the methacholine dose-response curve, was significantly higher in the WT than in the CD38KO mice. The rate of isometric force generation in tracheal segments (e.g., smooth muscle reactivity) was greater in the WT than in the CD38KO mice following incubation with IL-13. IL-13 treatment reduced isoproterenol-induced relaxations to similar magnitudes in tracheal segments obtained from WT and CD38KO mice. Both WT and CD38KO mice developed significant bronchoalveolar and parenchymal inflammation after IL-13 challenges compared with naïve controls. The results indicate that CD38 contributes to airway hyperresponsiveness in lungs exposed to IL-13 at least partly by increasing airway smooth muscle reactivity to contractile agonists.