Leukotriene B4 produces hyperalgesia that is dependent on polymorphonuclear leukocytes

The critical role of leukotriene B4 in antigen-induced mechanical hyperalgesia in immunised rats

1. We investigated the mediators responsible for mechanical hypersensitivity induced by antigen challenge in rats immunised with ovalbumin (OVA). 2. Challenge with OVA (12.5-100 micro g, intraplantar) caused a dose- and time-dependent mechanical hypersensitivity, which peaked 3 h after, decreased thereafter and reached control levels 24 h later. 3. Levels of TNFalpha, IL-1beta and cytokine-induced neutrophil chemoattractant 1 (CINC-1) were increased in paw skin after antigen challenge. 4. OVA-evoked hypersensitivity was partially inhibited (about 51%) by pretreatment with anti-TNFalpha, IL-1beta and IL-8 sera or with IL-1 receptor antagonist (IL-1ra), but not anti-NGF serum. Pretreatment with thalidomide (45 mg kg(-1)) or pentoxifylline (100 mg kg(-1)) also partially inhibited the hypersensitivity at 1-3 h after challenge. 5. Pretreatment with indomethacin (5 mg kg(-1)) or atenolol (1 mg kg(-1)) reduced the OVA-induced hypersensitivity at 1 and 3 h, but not at 5 h after challenge, while the combination of B(1) and B(2) bradykinin receptor antagonists was ineffective over the same times. 6. Pretreatment with MK886 (5-lipoxygenase-activating protein inhibitor, 3 mg kg(-1)), CP 105696 (LTB(4) receptor antagonist; 3 mg kg(-1)) or dexamethasone (0.5 mg kg(-1)) inhibited the hypersensitivity from 1 to 5 h. Furthermore, LTB(4) levels were increased in the paw skin of challenged rats. 7. In conclusion, our results suggest that the TNFalpha-, IL-1beta- and CINC-1-driven release of prostaglandins, sympathetic amines and LTB(4) mediates the first 3 h of mechanical hypersensitivity induced by antigen challenge in rats. At 5 h after OVA administration, although TNFalpha has some role, LTB(4) is the critical nociceptive mediator.

Platelets abrogate leukotriene B(4) generation by human blood neutrophils stimulated with monosodium urate monohydrate or f-Met-Leu-Phe in vitro

Neutrophils are physiologically associated with platelets in whole blood. Inflammatory reactions can be modulated by the presence of platelets. To investigate the influence of platelets on neutrophil activity, we studied the 5-lipoxygenase (5-LOX) metabolic pathway in normal human blood neutrophils stimulated with f-Met-Leu-Phe (fMLP) or monosodium urate monohydrate (MSUM) in the presence of autologous platelets. Platelets inhibited by more than 90% the synthesis of leukotriene B(4) and 5-HETE in neutrophils activated with fMLP or MSUM. The addition of exogenous arachidonic acid did not reverse the inhibitory effect of platelets on 5-LOX-generated metabolites in fMLP- or MSUM-activated neutrophils. Preincubation of neutrophils with adenosine deaminase reversed the inhibitory effect of platelets in fMLP-treated neutrophils, indicating that adenosine was responsible for the platelet inhibition of leukotriene B(4) and 5-HETE formation. In contrast, adenosine deaminase had no influence on the inhibitory effects of platelets in MSUM-stimulated cells. These results suggest that platelets can inhibit the synthesis of 5-LOX products (a). by acting mainly downstream to phospholipase A(2) in cells stimulated by fMLP or MSUM, (b). through adenosine when neutrophils are activated with fMLP, and (c). by an adenosine-independent mechanism in MSUM-activated neutrophils by an as-yet-unidentified mediator.

Synthesis of potent leukotriene A(4) hydrolase inhibitors. Identification of 3-[methyl[3-[4-(phenylmethyl)phenoxy]propyl]amino]propanoic acid

Leukotriene B(4) (LTB(4)) is a potent, proinflammatory mediator involved in the pathogenesis of a number of diseases including inflammatory bowel disease, psoriasis, rheumatoid arthritis, and asthma. The enzyme LTA(4) hydrolase represents an attractive target for pharmacological intervention in these disease states, since the action of this enzyme is the rate-limiting step in the production of LTB(4). Our previous efforts focused on the exploration of a series of analogues related to screening hit SC-22716 (1, 1-[2-(4-phenylphenoxy)ethyl]pyrrolidine) and resulted in the identification of potent, orally active inhibitors such as 2. Additional structure-activity relationship studies around this structural class resulted in the identification of a series of alpha-, beta-, and gamma-amino acid analogues that are potent inhibitors of the LTA(4) hydrolase enzyme and demonstrated good oral activity in a mouse ex vivo whole blood LTB(4) production assay. The efforts leading to the identification of clinical candidate SC-57461A (8d, 3-[methyl[3-[4-(phenylmethyl)phenoxy]propyl]amino]propanoic acid) are described.

A pyrroloquinazoline derivative with anti-inflammatory and analgesic activity by dual inhibition of cyclo-oxygenase-2 and 5-lipoxygenase

In a previous study, we reported a new pyrroloquinazoline derivative, 3-(4'-acetoxy-3',5'-dimethoxy)benzylidene-1,2-dihydropyrrolo[2,1-b]quinazoline-9-one (PQ), which inhibited human purified 5-lipoxygenase activity and prostaglandin E2 release in lipopolysaccharide-stimulated RAW 264.7 cells. In the present work, we show that PQ inhibits cyclo-oxygenase-2 activity in intact cell assays (human monocytes) and purified enzyme preparations (ovine isoenzymes) without affecting cyclo-oxygenase-1 activity. This behaviour was confirmed in vivo by using the zymosan-injected mouse air pouch model, where PQ caused a marked reduction in cell migration and leukotriene B4 levels at 4 h, as well as inhibition of prostaglandin E2 levels without affecting cyclo-oxygenase-2 expression at 24 h after zymosan stimulation. In addition, oral administration of this compound significantly reduced carrageenan-induced mouse paw oedema and phenyl-p-benzoquinone-induced writhings in mice. These results indicate that oral PQ exerts analgesic and anti-inflammatory effects, which are related to dual inhibition of cyclo-oxygenase-2 and 5-lipoxygenase activities.

Presurgical ketoprofen, but not morphine, dipyrone, diclofenac or tenoxicam, preempts post-incisional mechanical allodynia in rats

The treatment of pain before it initiates may prevent the persistent pain-induced changes in the central nervous system that amplify pain long after the initial stimulus. The effects of pre- or postoperative intraperitoneal administration of morphine (2 to 8 mg/kg), dipyrone (40 and 80 mg/kg), diclofenac (2 to 8 mg/kg), ketoprofen (10 and 20 mg/kg), and tenoxicam (10 and 20 mg/kg) were studied in a rat model of post-incisional pain. Groups of 5 to 8 male Wistar rats (140-160 g) were used to test each drug dose. An incision was made on the plantar surface of a hind paw and the changes in the withdrawal threshold to mechanical stimulation were evaluated with Von Frey filaments at 1, 2, 6 and 24 h after the surgery. Tenoxicam was given 12 or 6 h preoperatively, whereas the remaining drugs were given 2 h or 30 min preoperatively. Postoperative drugs were all given 5 min after surgery. No drug abolished allodynia when injected before or after surgery, but thresholds were significantly higher than in control during up to 2 h following ketoprofen, 6 h following diclofenac, and 24 h following morphine, dipyrone or tenoxicam when drugs were injected postoperatively. Significant differences between pre- and postoperative treatments were obtained only with ketoprofen administered 30 min before surgery. Preoperative (2 h) intraplantar, but not intrathecal, ketoprofen reduced the post-incisional pain for up to 24 h after surgery. It is concluded that stimuli generated in the inflamed tissue, rather than changes in the central nervous system are relevant for the persistence of pain in the model of post-incisional pain.

Neuroimmune alterations in the complex regional pain syndrome

This review focuses on some clinical aspects of the complex regional pain syndrome, such as oedema, local temperature changes and chronic pain, as a result of supposed neurogenic inflammation. Involvement of the immune system could imply the subsequent release of neuropeptides, pro-inflammatory cytokines and eicosanoids, which in turn leads to a complex cross-talk of primary and secondary generated mediators of inflammation. The development and application of drugs that act through selective receptor antagonism or enzymatic synthesis inhibition to prevent further stimulation of this cascade that could inevitably lead to chronicity of this disease are extensively discussed.

Pharmacological modulation of hyperalgesia induced by Bothrops asper (terciopelo) snake venom

The ability of Bothrops asper snake venom to cause hyperalgesia was investigated in rats, using the paw pressure test. Intraplantar injection of the venom (5-15 microg/paw) caused a dose and time-related hyperalgesia, which peaked 2h after venom injection. Bothrops asper venom-induced hyperalgesia was blocked by the bradykinin B(2) receptor antagonist HOE 140 and attenuated by dexamethasone, an inhibitor of phospholipase A(2). Inhibition of the lipoxygenase pathway by NDGA abrogated the algogenic phenomenon. The hyperalgesic response was not modified by pretreatment with indomethacin, an inhibitor of the cyclo-oxygenase pathway, by meloxicam, an inhibitor of the type 2 cyclo-oxygenase pathway, by the PAF receptor antagonist BN52021 or by anti-TNF-alpha or anti-interleukin 1 antibodies. Intraplantar injection of the venom also caused an oedematogenic response which was not modified by any of these pharmacological treatments. These results suggest that hyperalgesia induced by Bothrops asper venom is, at least partially, mediated by bradykinin, phospholipase A(2) activity and leukotrienes. Distinct mechanisms are involved in the development of hyperalgesia and oedema induced by the venom.

Role of cysteinyl leukotrienes in nociceptive and inflammatory conditions in experimental animals

The leukotrienes are potent inflammatory mediators, which may have a role in inflammatory diseases such as allergic rhinitis, inflammatory bowl disease and asthma. Zafirlukast, a cysteinyl leukotriene receptor antagonist, is claimed to be effective in asthma. However, it is not known whether these leukotrienes are involved in nociceptive and peripheral inflammation. The present study aimed to assess the role of cysteinyl leukotrienes in nociceptive and inflammatory conditions in experimental animals. Central nociception was assessed with tail-flick and hot-plate methods and peripheral nociception was assessed by acetic acid-induced chemonociception in mice. Local administration (intraplantar) of carrageenan-induced hyperalgesia and inflammation, measured by paw withdrawal latency and paw volumes, respectively. Zafirlukast (2.5--20 mg/kg, p.o.) produced a significant and dose-dependent antinociceptive and antiinflammatory effect against acetic acid-induced chemonociception in mice and carrageenan-induced paw oedema in rats, respectively. Zafirlukast (2.5 and 5.0 mg/kg, p.o.) also attenuated the carrageenan-provoked hyperalgesia but did not alter the pain threshold in central nociception up to 20 mg/kg. Zafirlukast (5 and 10 mg/kg ) significantly inhibited exudate formation and migration of polymorphonuclear leukocytes in carrageenan-induced pleurisy. Further, zafirlukast (5 mg/kg) also reduced myeloperoxidase activity in carrageenan-treated paw. When nimesulide (2 mg/kg, p.o.) was co-administered with zafirlukast, the antinociceptive, antihyperalgesic and antiinflammatory effects of nimesulide were significantly increased as compared to the per se effect. The results indicate that cysteinyl leukotrienes are involved in nociceptive/inflammatory conditions. It is expected that combination of cysteinyl leukotriene receptor antagonist with cyclooxygenase inhibitor would prove to be a novel approach to treat complex inflammatory conditions.

Roles of thromboxane A2 and leukotriene B4 in radicular pain induced by herniated nucleus pulposus

Biologically active substances, such as prostaglandins, thromboxanes, and leukotrienes, which are metabolites involved in the arachidonic acid cascade, are detected in herniated disc samples obtained from patients with lumbar disc herniation. However, little is known concerning the relationships between these substances and clinical symptoms such as radicular pain. Thromboxane A2 (TXA2) induces not only potent platelet aggregation, but also blood vessel contraction. Leukotriene B4 (LTB4), a potent chemotactic agent, plays a role in inflammatory reactions by recruiting neutrophils and lymphocytes. The purpose of this study was to examine the roles of TXA2 and LTB4 in the hyperalgesia induced by application of nucleus pulposus to the lumbar nerve root in the rat. TXA2 synthetase inhibitor and LTB4 receptor antagonist, which were injected into the epidural space, decreased mechanical hyperalgesia at both three and seven days after epidural injection. There were no significant differences in sensitivity to noxious thermal stimuli following application of the nucleus pulposus or an epidural injection. Epidural injection of LTB4 receptor antagonist and/or TXA2 synthetase inhibitor may attenuate the painful radiculopathy due to lumbar disc herniation. In conclusion, our findings suggest that TXA2 and LTB4 may play significant roles in mechanical hyperalgesia induced by autologous nucleus pulposus.

Hyperalgesia due to nerve injury: role of neutrophils

The hypothesis that the early inflammatory cell, the neutrophil, contributes to the hyperalgesia resulting from peripheral nerve injury was tested in rats in which the sciatic nerve was partially transected on one side. The extent and time-course of neutrophilic infiltration of the sciatic nerve and innervated paw skin after partial nerve damage was characterized using immunocytochemistry. The number of endoneurial neutrophils was significantly elevated in sections of operated nerve compared to sections of sham-operated nerve for the entire period studied, i.e. up to seven days post-surgery. This considerable elevation in endoneurial neutrophil numbers was only observed at the site of nerve injury. Depletion of circulating neutrophils at the time of nerve injury significantly attenuated the induction of hyperalgesia. However, depletion of circulating neutrophils at day 8 post-injury did not alleviate hyperalgesia after its normal induction. It is concluded that endoneurial accumulation of neutrophils at the site of peripheral nerve injury is important in the early genesis of the resultant hyperalgesia. The findings support the notion that a neuroimmune interaction occurs as a result of peripheral nerve injury and is important in the subsequent development of neuropathic pain.

Defective metabolism of leukotriene B4 in the Sjögren-Larsson syndrome

The Sjögren-Larsson Syndrome (SLS) is a neurocutaneous disorder, caused by deficient activity of the microsomal enzyme fatty aldehyde dehydrogenase (FALDH). FALDH catalyzes the oxidation of medium- and long-chain fatty aldehydes to their corresponding carboxylic acids. SLS is diagnosed by demonstrating the enzyme deficiency or by mutation analysis of the FALDH gene, while laboratory investigations of plasma, urine, and cerebrospinal fluid do not reveal any diagnostic abnormality. Leukotriene (LT) B4 is a pro-inflammatory mediator synthesized from arachidonic acid. LTB4 is inactivated by microsomal omega-oxidation, successively yielding 20-OH-LTB4, 20-CHO-LTB4 and 20-COOH-LTB4. Since FALDH is involved in LTB4 degradation, we have analyzed LTB4 and its metabolites in urine and cerebrospinal fluid as well as the degradation capacity for LTB4 in fresh polymorphonuclear leukocytes (PMN) of SLS patients. The urinary concentrations of LTB4, 20-OH-LTB4 and 20-COOH-LTB4 are below the detection limit in healthy controls. The urine of all SLS patients (n=13) exhibited highly elevated concentrations of LTB4 and 20-OH-LTB4, while 20-COOH-LTB4 was absent. Cerebrospinal fluid levels of LTB4, 20-OH-LTB4 and 20-COOH-LTB4 were found to be normal (n=7). PMN isolated from four patients were shown to be unable to convert 20-OH-LTB4 to 20-COOH-LTB4. Our findings provide unambiguous evidence for defective LTB4 degradation in SLS patients, and offer new and non-invasive diagnostic tools. Moreover, they open new pathophysiological considerations, with the prospect of rational treatment strategies.

A novel hepatointestinal leukotriene B4 receptor. Cloning and functional characterization

Leukotriene B(4) (LTB(4)) is a product of eicosanoid metabolism and acts as an extremely potent chemotactic mediator for inflammation. LTB(4) exerts positive effects on the immigration and activation of leukocytes. These effects suggest an involvement of LTB(4) in several diseases: inflammatory bowel disease, psoriasis, arthritis, and asthma. LTB(4) elicits actions through interaction with one or more cell surface receptors that lead to chemotaxis and inflammation. One leukotriene B(4) receptor has been recently identified (LTB(4)-R1). In this report we describe cloning of a cDNA encoding a novel 358-amino acid receptor (LTB(4)-R2) that possesses seven membrane-spanning domains and is homologous (42%) and genetically linked to LTB(4)-R1. Expression of LTB(4)-R2 is broad but highest in liver, intestine, spleen, and kidney. In radioligand binding assays, membranes prepared from COS-7 cells transfected with LTB(4)-R2 cDNA displayed high affinity (K(d) = 0.17 nm) for [(3)H]LTB(4). Radioligand competition assays revealed high affinities of the receptor for LTB(4) and LTB(5), and 20-hydroxy-LTB(4), and intermediate affinities for 15(S)-HETE and 12-oxo-ETE. Three LTB(4) receptor antagonists, 14,15-dehydro-LTB(4), LTB(4)-3-aminopropylamide, and U-75302, had high affinity for LTB(4)-R1 but not for LTB(4)-R2. No apparent affinity binding for the receptors was detected for the CysLT1-selective antagonists montelukast and zafirlukast. LTB(4) functionally mobilized intracellular calcium and inhibited forskolin-stimulated cAMP production in 293 cells. The discovery of this new receptor should aid in further understanding the roles of LTB(4) in pathologies in these tissues and may provide a tool in identification of specific antagonists/agonists for potential therapeutic treatments.

Preliminary studies on the anti-inflammatory and analgesic activity of the methanolic fraction of the root extract of Tragia involucrata Linn

Tragia involucrata has been widely used in the traditional medicinal system for the treatment of a variety of diseases. The effect of methanolic extract of T. involucrata was studied in different experimental animal models and it was revealed that the extract possesses significant analgesic and anti-inflammatory activity.

Direct activation of capsaicin receptors by products of lipoxygenases: endogenous capsaicin-like substances

Capsaicin, a pungent ingredient of hot peppers, causes excitation of small sensory neurons, and thereby produces severe pain. A nonselective cation channel activated by capsaicin has been identified in sensory neurons and a cDNA encoding the channel has been cloned recently. However, an endogenous activator of the receptor has not yet been found. In this study, we show that several products of lipoxygenases directly activate the capsaicin-activated channel in isolated membrane patches of sensory neurons. Among them, 12- and 15-(S)-hydroperoxyeicosatetraenoic acids, 5- and 15-(S)-hydroxyeicosatetraenoic acids, and leukotriene B(4) possessed the highest potency. The eicosanoids also activated the cloned capsaicin receptor (VR1) expressed in HEK cells. Prostaglandins and unsaturated fatty acids failed to activate the channel. These results suggest a novel signaling mechanism underlying the pain sensory transduction.

Synthesis and analgesic activity of novel N-acylarylhydrazones and isosters, derived from natural safrole

Anew series of antinociceptive compounds belonging to the N-acylarylhydrazone (NAH) class were synthesized from natural safrole (7). The most analgesic derivative represented by 10f, [(4'-N,N-dimethylaminobenzylidene-3-(3', 4'-methylenedioxyphenyl)propionylhydrazine], was more potent than dipyrone and indomethacin, used as standards. The NAH compounds described herein were structurally planned by molecular hybridization and classical bioisosterism strategies on previously reported analgesic NAH in order to identify the pharmacophoric contribution of the N-acylarylhydrazone moiety and investigate the structure-activity relationship (SAR) in these series.

The antinociceptive effect of leukotriene D(4) receptor antagonist, MK-571, in mice: possible involvement of opioidergic mechanism

The effect of a leukotriene D(4) receptor antagonist, (3-(3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl(3-dimethyl amino-3-oxo propyl)thio)methyl)thio) propanoic acid (L-660,711; MK-571), was investigated on nociceptive responses in mice using three different assays: acetic-acid-induced abdominal constrictions, formalin response and tail-flick test. MK-571 (8-32 mg/kg, i.v.) produced dose-dependent protection against acetic-acid-induced abdominal constriction (ED(50)=30 mg/kg). The compound (10-80 mg/kg, i.p.) was also effective, in a dose-dependent manner, on the second phase of the formalin response (ED(50)=26 mg/kg). However, it had no effect on the first phase of the formalin response and in the tail-flick test. Naloxone (1 mg/kg, i.v.), an opioid antagonist, almost completely blocked the antinociceptive effect of MK-571 in both acetic-acid-induced abdominal constriction and the second phase of the formalin test. These results provide evidence for an antinociceptive action of MK-571 at peripheral sites and suggest that opioid mechanisms are involved.

The induction of pain: an integrative review

The highly disagreeable sensation of pain results from an extraordinarily complex and interactive series of mechanisms integrated at all levels of the neuroaxis, from the periphery, via the dorsal horn to higher cerebral structures. Pain is usually elicited by the activation of specific nociceptors ('nociceptive pain'). However, it may also result from injury to sensory fibres, or from damage to the CNS itself ('neuropathic pain'). Although acute and subchronic, nociceptive pain fulfils a warning role, chronic and/or severe nociceptive and neuropathic pain is maladaptive. Recent years have seen a progressive unravelling of the neuroanatomical circuits and cellular mechanisms underlying the induction of pain. In addition to familiar inflammatory mediators, such as prostaglandins and bradykinin, potentially-important, pronociceptive roles have been proposed for a variety of 'exotic' species, including protons, ATP, cytokines, neurotrophins (growth factors) and nitric oxide. Further, both in the periphery and in the CNS, non-neuronal glial and immunecompetent cells have been shown to play a modulatory role in the response to inflammation and injury, and in processes modifying nociception. In the dorsal horn of the spinal cord, wherein the primary processing of nociceptive information occurs, N-methyl-D-aspartate receptors are activated by glutamate released from nocisponsive afferent fibres. Their activation plays a key role in the induction of neuronal sensitization, a process underlying prolonged painful states. In addition, upon peripheral nerve injury, a reduction of inhibitory interneurone tone in the dorsal horn exacerbates sensitized states and further enhance nociception. As concerns the transfer of nociceptive information to the brain, several pathways other than the classical spinothalamic tract are of importance: for example, the postsynaptic dorsal column pathway. In discussing the roles of supraspinal structures in pain sensation, differences between its 'discriminative-sensory' and 'affective-cognitive' dimensions should be emphasized. The purpose of the present article is to provide a global account of mechanisms involved in the induction of pain. Particular attention is focused on cellular aspects and on the consequences of peripheral nerve injury. In the first part of the review, neuronal pathways for the transmission of nociceptive information from peripheral nerve terminals to the dorsal horn, and therefrom to higher centres, are outlined. This neuronal framework is then exploited for a consideration of peripheral, spinal and supraspinal mechanisms involved in the induction of pain by stimulation of peripheral nociceptors, by peripheral nerve injury and by damage to the CNS itself. Finally, a hypothesis is forwarded that neurotrophins may play an important role in central, adaptive mechanisms modulating nociception. An improved understanding of the origins of pain should facilitate the development of novel strategies for its more effective treatment.

The role of inflammation in disk herniation-associated radiculopathy

OBJECTIVE

The causes and physiopathology of low-back pain and acute lumbar radiculopathy remain unclear. A compression of the nerve root by protruded disk has been suggested but explains only partially the physiopathology of radicular pain. This article provides an overview of the role of inflammation in disk herniation-associated radiculopathy.

METHODS

A review of the relevant literature in American and European medical journals was performed.

RESULTS

Several studies have identified inflammatory mediators (phospholipase A2, prostaglandin E2, leukotrienes, nitric oxide, immunoglobulins, pro-inflammatory cytokines such as interleukin [IL]-1alpha, IL-1beta, IL-6, and tumor necrosis factor alpha [TNFalpha]) and autoimmune reaction (macrophages expressing IL-1beta, intercellular adhesion molecules) in disk herniation. An appealing hypothesis is that the leakage of these agents may produce an excitation of the nociceptors, a direct neural injury, a nerve inflammation, or an enhancement of sensitization to other pain-producing substances (such as bradykinin), leading to the nerve root pain. However, the role of these inflammatory mediators in the pathophysiology of lumbar radiculopathy has not been proven. Several findings suggest that this inflammatory response, which occurs in the early stage of disk herniation, is transient. Indeed, most studies of chronic disk herniation samples failed to demonstrate inflammation.

CONCLUSION

Although inflammation may partially explain lumbar radiculopathy, involvement of inflammatory mediators in the physiopathology of disk herniation-associated radiculopathy has not been proven.

A randomized clinical trial of the nonsteroidal eyedrop diclofenac after strabismus surgery

OBJECTIVE

This study aimed to compare the anti-inflammatory and analgesic effects of topical diclofenac sodium 0.1% (Voltaren) with prednisolone sodium phosphate 1% ophthalmic solution after strabismus surgery.

DESIGN

A prospective, double-masked, randomized, two-center clinical trial.

PARTICIPANTS

Eighty eyes of 52 patients undergoing strabismus surgery were examined.

INTERVENTION

For 1 week after surgery, the eye that was operated on received one drop of either diclofenac or prednisolone four times a day.

MAIN OUTCOME MEASURES

The diclofenac- and prednisolone-treated eyes were compared on postoperative days 3 and 7 with respect to signs of inflammation (e.g., erythema, edema, discharge), patient comfort, and conjunctival incisional healing.

RESULTS

On postoperative day 7, in eyes that received prednisolone, the conjunctival defects were larger (P = 0.004) and more frequent (P = 0.02). For all subjects, despite adequate statistical power, there was no statistically significant difference in inflammatory scores between eyes that received diclofenac or prednisolone. In cases of bilateral surgery, however, there was less postoperative erythema and edema in the diclofenac-treated eyes.

CONCLUSIONS

In the first week after strabismus surgery, topical diclofenac proved at least as effective as prednisolone in controlling inflammation and discomfort with less delay in incisional wound healing. Topical diclofenac, a nonsteroidal anti-inflammatory agent, may be considered for use after strabismus surgery in place of corticosteroids.

High-dose methylprednisolone prevents extensive sick leave after whiplash injury. A prospective, randomized, double-blind study

STUDY DESIGN

A prospective, randomized, double-blind study comparing high-dose methylprednisolone with placebo.

OBJECTIVES

To evaluate the efficacy of high-dose methylprednisolone when administered within 8 hours after whiplash injury.

SUMMARY OF BACKGROUND DATA

Whiplash injury often results in chronic symptoms. The management of whiplash injuries is controversial, and pharmacologic therapy has received little evaluation. In recent reports, dysfunction of the central nervous system has been indicated in several cases. Methylprednisolone administered within 8 hours after the injury to patients with acute spinal cord injury has been demonstrated to improve the outcome. This procedure was also adopted in a randomized study of cases of whiplash injury in car accidents.

METHODS

Forty patients, 22 men and 18 women with a mean age of 35 years (range, 19-65), were included in the study, 20 in each of two groups. They were treated for whiplash injury, which they had sustained in car accidents. The patients were enrolled if their diagnoses were complete and treatment had begun within 8 hours after injury. Disabling symptoms severe enough to prevent the patient from returning to work, number of sick days before and after injury, and sick-leave profile after injury were used as parameters for the evaluation of the effects of the treatment. Baseline demographic data were controlled for when statistical analysis had been performed.

RESULTS

At the follow-up examination 6 months after initial treatment, there was a significant difference in disabling symptoms between the actively treated patients and the placebo group (P = 0.047), total number of sick days (P = 0.01), and sick-leave profile (P = 0.003).

CONCLUSIONS

The results of this study indicate that acute treatment with high-dose methylprednisolone may be beneficial in preventing extensive sick leave after whiplash injury. However, the number of patients studied was small, and therefore further prospective, controlled studies are needed.

Interleukin-5-producing CD4+ T cells play a pivotal role in aeroallergen-induced eosinophilia, bronchial hyperreactivity, and lung damage in mice

Although activated CD4+ T cells have been implicated in the pathogenesis of asthma, the direct contribution of this leukocyte to the induction of aeroallergen-induced bronchial hyperreactivity and lung damage is unknown. In the present investigation, we have used a model of allergic airways inflammation, which displays certain phenotypic characteristics of late-phase asthmatic responses, together with interleukin-5-deficient (IL-5-/- ) mice and donor antigen-specific CD4+ TH2-type cells to obtain unequivocal evidence for a role of this T lymphocyte in the pathophysiology of allergic airways inflammation. Antigen-primed CD4+ T cells and CD4- cells (CD4+-depleted population) were purified from the spleens of ovalbumin (OVA)-sensitized wild-type mice and adoptively transferred to OVA-sensitized and nonsensitized IL-5-/- mice. In vitro stimulation of the purified cell populations with OVA resulted in the secretion of IL-4 and IL-5, but not interferon-gamma, from the CD4+ T cells, indicating that they were of the TH2 type. In contrast, interferon-gamma, but not IL-4 and IL-5, was produced by the CD4- T cells. The CD4+ TH2-type cells (but not the CD4 cells) reconstituted aeroallergen (OVA)-induced blood and airways eosinophilia, lung damage, and airways hyperreactivity to 1-methacholine in IL-5-/- mice. The reconstitution did not require prior sensitization of the mice, but it did not occur if they were aerosolized with saline instead of OVA. The circulating levels of OVA-specific -IgE and -IgG1 were not significantly altered by the adoptive transfer of either cell population. These investigations establish that IL-5-secreting CD4+ TH2-type cells play a pivotal role in generating blood and airways eosinophilia and in the subsequent development of bronchial hyperreactivity and lung damage that occurs in response to aeroallergens.

The inflammatory properties of contained and noncontained lumbar disc herniation

STUDY DESIGN

The inflammatory properties of nucleus pulposus were assessed in biopsy samples from patients who underwent surgery for lumbar disc herniation.

OBJECTIVES

To investigate the inflammatory properties of the different types of disc herniation.

BACKGROUND DATA

High levels of phospholipase A2 previously have been demonstrated in a small number of patients undergoing lumbar disc surgery. Phospholipase A2 is the enzyme responsible for the liberation of arachidonic acid from cell membranes at the site of inflammation and is considered to be the limiting agent in the production of prostaglandins and leukotrienes, which are powerful mediators of inflammation. Cytokines are among the many agonists inducing phospholipase A2 activation. Several reports previously have demonstrated the difference in clinical appearance of different types of lumbar disc herniation.

METHODS

Thirty-seven patients undergoing surgery for lumbar disc herniation were investigated. During surgery the disc pathology of each patient was classified into one of three groups: bulging disc, contained herniation, and noncontained disc herniation. Also during surgery, biopsy samples were taken from the nucleus, immediately frozen in liquid nitrogen, and subsequently stored at -70 C until analyzed.

RESULTS

No traces of interleukin-6 or tumor necrosis factor alpha were found in the biopsy samples. There was a significant difference in the levels of leukotriene B4 and thromboxane B2 in contained versus noncontained disc herniation, and the highest concentration was found in the noncontained disc herniation group.

CONCLUSION

The results support the theory that inflammatory mechanisms are involved in sciatica because of lumbar disc herniation and indicate that the different types of disc herniation have different inflammatory properties.

Nonsteroidal anti-inflammatory drugs and corticosteroids for the management of canine osteoarthritis

Anti-inflammatory medications have long been prescribed for relief of the pain and discomfort associated with OA. This occurs despite the recognized side effects associated with use of NSAIDs and corticosteroids. Available evidence suggests that NSAIDs provide this relief through a combination of central and peripheral actions. Recent discovery of two isoforms of cyclooxygenase has increased our understanding of NSAID activity and may result in identification of drugs that potentially will have fewer side effects. A review of NSAIDs used in veterinary medicine indicates that relatively little is known regarding their role in treating OA, although controlled studies involving carprofen and etodolac have increased our knowledge of the efficacy of specific NSAIDs used for this purpose.

Transpedicle instrumentation in the degenerative spine

Controversy continues regarding the use of pedicle instrumentation in fusion surgery on the degenerative lumbar spine. Recently, however, published reports are increasingly demonstrative of the positive effect of pedicle fixation on fusion and outcome success in the management of these disorders. Recent developments in surgical technique and implant design have improved operative risk and implant related complications. However, patient selection and demonstration of the underlying pathophysiology of degenerative lumbar motion segment pain remain 2 of the main challenges to clinical practice. The importance of well designed clinical studies are of paramount consequence in the solution of the existing controversies surrounding surgical treatment of the degenerative lumbar spine. Equally significant is the need to establish general and accepted measures of outcome to assess and compare treatment options. Combining study design and accepted outcome assessment will permit the resolution of the remaining controversies. The future of pedicle instrumentation of the degenerative lumbar spine is of necessity tied to the resolution of these remaining points of controversy-only thereafter can the current rate of advances continue.

NSAIDs revisited: selection, monitoring, and safe use

Although nonsteroidal anti-inflammatory drugs (NSAIDs) are effective analgesic and anti-inflammatory agents, they may have adverse effects on the gastrointestinal, hepatic, renal, pulmonary, and platelet aggregation systems in susceptible patients. Careful consideration of the risks and benefits, judicious dosing, and careful monitoring by the primary care physician are therefore essential. The authors of this article review both the therapeutic and adverse effects of NSAIDs and provide suggestions for safe clinical use.

Role of peridural fibrosis in the failed back: a review

Failed back surgery syndrome (FBSS) is the presence of persistent, disabling pain in the hip, thigh, leg, or lower back of a patient who has undergone a laminectomy or discectomy. Some degree of FBSS is found in approximately 15% of such patients. There may be a direct relationship between the extent of pathology found during the initial surgical procedure and the probability that FBSS will develop. Although FBSS is usually due to improper diagnosis and surgery, another important cause is peridural fibrosis. Part of the answer may have to do with neuromechanics. In a healthy person, pain associated with dural and nerve root movement does not typically occur when performing activities of daily living. In contrast, in a person with peridural scarring, the dura and nerve roots are bound by fibrosis, and putting traction on the nerve roots and dura by back and limb movement produces pain. This pain is aggravated by the presence of inflammation at the surgical site. Research has shown that disc herniation activates the arachidonic acid cascade, resulting in the production of prostaglandins E1 and E2 and leukotriene B, substances that contribute to an inflammatory process that persists after discectomy. In an attempt to inhibit peridural fibrosis, methylprednisolone, polyethylene films, and fat grafts have been applied to the dura after discectomy. These experimental treatments have had limited success. Development of a therapy that reliably prevents peridural adhesive fibrosis will reduce the incidence of FBSS.

Human group II phospholipase A2 in normal and diseased intervertebral discs

We measured calcium-dependent phospholipase A2 (PLA2) activity and immunoreactive group II PLA2 levels of 54 normal discs obtained from cadavers and 73 disc samples surgically obtained from patients with spinal disorders, including intervertebral disc herniations, spondylosis, and spondylolisthesis. Both cadaveric and surgical disc specimens contained about two-fold greater PLA2 activity than the ileal mucosa, one of the richest sources of group II PLA2. Discs of middle-aged cases had significantly higher activity than those of younger and elder cases. In cadaveric normal discs, calcium-dependent PLA2 activity was significantly higher in females than in males. Annulus fibrosus and nucleus pulposus contained the same PLA2 levels. In diseased disc, herniated fragments that had extruded or protruded out of the discs possessed lower activity than other parts of discs in the intervertebral space. Immunoreactive group II PLA2 levels of intervertebral discs closely correlated with PLA2 enzymatic activity. We purified a PLA2 from human intervertebral disc to homogeneity to further identify the isozymic nature of discal PLA2. Its NH2-terminal amino acid sequences and molecular weight were identical to those of human group II PLA2. Immunohistochemical analysis using a monoclonal anti-group II PLA2 antibody showed that in both annulus fibrosus and nucleus pulposus chondrocytes contained intense group II PLA2 immunoreactivity in their cytoplasm, and that the matrix contained no substantial immunoreactivity. These results suggest that group II PLA2 in chondrocytes has important physiological roles in discal ordinary metabolism, maintaining discal homeostasis.

Prostaglandin production after experimental discectomy

STUDY DESIGN

This study ascertained the effects of discectomy on prostaglandin synthesis.

OBJECTIVES

The purpose of these novel experiments was to measure the levels of two prostaglandins in lumbar epidural fluid obtained from an area subjected to discectomy. For comparison, lumbar epidural fluid from a site not disturbed by discectomy and fluid from a subcutaneous site were analyzed for the prostaglandins.

SUMMARY OF BACKGROUND DATA

Previous studies have shown that nuclear material obtained from degenerative discs manifests an extraordinarily high level of phospholipase A2 activity. Others have hypothesized that the known inflammatory effects of phospholipase A2 are due to the release of arachidonic acid, which is converted to various eicosanoids, including several algesic prostaglandins (PGI2 and PGE2). No previous study has continuously measured prostaglandin levels in epidural fluid or assessed the effect of discectomy on prostaglandin production.

METHODS

An ultrafiltrate of lumbar epidural fluid of dogs was obtained from indwelling catheters located adjacent to spinal areas that were and were not subjected to discectomy as well as from subcutaneous tissue. The fluid was collected daily for 14 days and analyzed for PGE2 and 6-keto PGF1(alpha) (the stable metabolite of PGI2) by radioimmunoassay.

RESULTS

The concentration of 6-keto PGF1(alpha) and PGE2 in fluid collected during the first 24 hours was significantly higher in the area of discectomy than in the epidural region that was not subjected to discectomy and significantly higher than in fluid obtained from the subcutaneous site. The high level of these prostaglandins at the discectomy site fell rapidly, so that by the end of 48 hours the differences in values between spinal fluid from the discectomy and nondiscectomy regions were not statistically significant. The concentration of the prostaglandins in epidural fluid decreased with time and became minimal within the second week.

CONCLUSION

The removal of normal discs is accompanied for 24 hours by a marked rise in the synthesis of two prostaglandins known to produce pain. Because the concentration of prostaglandins in epidural fluid decreased rapidly thereafter, the initial surge obtained appears to be associated more with chemical factors such as phospholipase A2 than with wound healing.

Mechanisms of chronic pain

Chronic pain differs from acute pain in that it serves no useful function, causes suffering, limits activities of daily living, and increases costs of healthcare payments, disability, and litigation fees. Pain perception begins with activation of peripheral nociceptors and conduction through myelinated A delta and unmyelinated C fibers to the dorsal root ganglion. From here, signals travel via the spinothalamic tract to the thalamus and the somatosensory cortex. Modulation of sensory input (i.e., pain) occurs at many levels. Nociceptors are also neuroeffectors, and transmission can be modulated by their cell bodies, which secrete inflammatory mediators, neuropeptides, or other pain-producing substances. Descending pathways from the hypothalamus, which has opioid-sensitive receptors and is stimulated by arousal and emotional stress, can transmit signals to the dorsal horn that modulate ascending nociceptive transmissions. Modulation to alter the perception of pain also can occur at higher centers (e.g., frontal cortex, midbrain, medulla) by opioids, anti-inflammatory agents, as well as antagonists and agonists of neurotransmitters. This article will review our current knowledge of the mechanisms involved in (1) the transduction of tissue injury or disease signals (nociception and nociceptive receptors); (2) the transmission of signals rostrally to the thalamus and higher nervous system centers (involving perception of the quality, location, and intensity of noxious signals); and (3) the modulation of ascending sensory messages at all levels (periphery, spinal cord, and higher centers).

The effect of leukotriene synthesis inhibitors in models of acute and chronic inflammation

OBJECTIVE

To assess the efficacy of leukotriene synthesis inhibitors, alone and in combination with a nonsteroidal antiinflammatory drug, as potential treatments for rheumatoid arthritis (RA), using the mouse air pouch model and the collagen-induced arthritis (CIA) model.

METHODS

Two selective leukotriene synthesis inhibitors, Bay x 1005 and Bay y 1015, were compared with zileuton in terms of their ability to decrease exudate volume, cell infiltration, and leukotriene B4 (LTB4) production in response to zymosan injection in the mouse air pouch model. The mouse CIA model was used to assess the effect of leukotriene synthesis inhibitors in a model of chronic inflammation. Bay y 1015 and Bay x 1005, and the cyclooxygenase inhibitor naproxen, were evaluated individually and in combination, for their antiarthritic potency in the mouse CIA model.

RESULTS

The results indicate that neither zileuton, Bay x 1005, nor Bay y 1015 inhibited exudate production. All 3 compounds decreased LTB4 levels in be air pouch, with Bay y 1015 being the most effective. Cell infiltration was significantly decreased with Bay x 1005, but the degree of this decrease did not appear to correlate with LTB4 levels. No inhibition of arthritis was observed with any compound administered alone. In contrast, a significant inhibition of CIA was observed in animals that received both naproxen and either Bay y 1015 or Bay x 1005.

CONCLUSION

Inhibitors of both cyclooxygenase and leukotriene synthesis in combination may be a more effective treatment of RA than either class of inhibitors alone.

Role of lipoxygenase metabolites in platelet-activating factor- and antigen-induced bronchial hyperresponsiveness and eosinophil infiltration

The effect of a novel leuktriene B4 receptor antagonist N-[5[[8-(1-hydroxy-2- phenyl)ethyl]dibenzofuran-2yl]5-hydroxypentanoyl]pyrrolidine (PF 10042) has been evaluated in comparison with 2-[3(1-hydroxyhexyl)phenoxymethyl]quinoline hydrochloride (PF 5901), a specific inhibitor of the 5-lipoxygenase pathway of arachidonic acid metabolism, against platelet activating factor (PAF) and allergen induced bronchial hyperresponsiveness and pulmonary eosinophil infiltration in the guinea pig. PF 10042 significantly displaced radiolabelled [3H]leukotriene B4 from binding sites on human neutrophils with an EC50 of 3 muM. PF 10042 (100 mg/kg, i.p.) significantly inhibited PAF and allergen induced bronchial hyperresponsiveness without reducing the concomitant eosinophil infiltration, whereas PF 5901 (100 mg/kg, p.o.) significantly inhibited both PAF and allergen induced bronchial hyperresponsiveness and eosinophil infiltration. We suggest from these results that PAF and allergen induced bronchial hyperresponsiveness may be secondary to the release of leukotriene B4, but this lipoxygenase metabolite does not contribute significantly to the observed eosinophil infiltration.

Pain due to nerve damage: are inflammatory mediators involved?

Damage to peripheral nerves often results in pain and hyperalgesia. We suggest that nerve damage causes an inflammatory response in which cells associated with the nerve release inflammatory mediators such as eicosanoids; these mediators may contribute to the hyperalgesia which results from nerve injury. The cell types most likely to be responsible include macrophages and postganglionic sympathetic neurones. A better understanding of the mechanisms involved should lead to improved therapies for neuropathic pain.

Antinociceptive activity of filenadol on inflammatory pain

The novel analgesic filenadol (d, 1-erythro-1-(3',4'-methylenedioxyphenyl)-1- morpholinopropan-2-ol) inhibited phenyl-p-benzoquinone-induced writhing in mice with ID50 values of 68.8 (p.o.), 1.67 (i.v.) and 0.48 (i.c.v.) mg/kg. Hyperalgesia induced by arachidonic acid, PGE2 or LTB4 in this test was also decreased by filenadol (ID50 = 24.4, 3.7 and 50.1 mg/kg p.o., respectively). This compound was effective on PGE2, LTB4, bradykinin, PAF or IL-1 beta-induced decrease in pain threshold in the rat paw pressure model and almost totally suppressed the writhing induced by zymosan in mice, while peritoneal production of 6-ketoPGF1 alpha was inhibited by 48.5-62% and only at 100 mg/kg significant inhibition of LTC4 was achieved. The late phase of formalin-induced pain response in mice was prevented by filenadol, without affecting the oedema. Filenadol is an antinociceptive agent that reduces the hyperalgesic effects of inflammatory mediators besides inhibiting partially the synthesis of eicosanoids.

Eicosanoids, fatty acids and neutrophils: their relevance to the pathophysiology of disease

PUFA and their eicosanoid metabolites are potent biological modifiers. They have beneficial effects in a number of diseases, which may result in part from their direct actions on neutrophils as well as from their ability to modulate eicosanoid biosynthesis. A consideration of their interactions with other cell types, e.g. lymphocytes and macrophages, is beyond the scope of this review. Small alterations in structure can result in large changes in the neutrophil response. This will have important implications for the further development and use of fatty acids for therapeutic purposes.

Mu-opioid agonist enhancement of prostaglandin-induced hyperalgesia in the rat: a G-protein beta gamma subunit-mediated effect?

Guanine nucleotide-binding regulatory protein stimulation of adenylyl cyclase has been shown to be an important second messenger system for many processes, including mechanical hyperalgesia. Recently, interactions between guanine nucleotide-binding regulatory protein subunits and adenylyl cyclase affecting the level of cyclic adenosine 3',5'-monophosphate accumulation have been demonstrated. In this study we evaluated such an interaction by measuring paw-withdrawal thresholds to mechanical stimuli in Sprague-Dawley rats in the presence of two direct-acting hyperalgesic agents, prostaglandin E2 and the adenosine A2-agonist, CGS21680. The effects of two agents expected to liberate inhibitory guanine nucleotide-binding regulatory protein subunits were also studied: [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (a mu-opioid receptor agonist) and N6-cyclopentyladenosine (an A1-adenosine agonist). Injection of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin immediately before prostaglandin E2 or CGS21680 significantly attenuated the hyperalgesia subsequently induced by these agents, i.e. the sensitivity to these hyperalgesic agents was decreased. On the other hand, injection of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin 5 min after prostaglandin E2 or CGS21680 significantly enhanced the hyperalgesia observed. Injection of the adenosine A1-agonist N6-cyclopentyladenosine immediately before and 5 min after prostaglandin E2 or CGS21680 had a similar effect to [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin. The decrease in sensitivity to prostaglandin E2- and CGS21680-induced hyperalgesia by preadministration of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin or N6-cyclopentyladenosine and the enhancement by postadministration were all reversed by pertussis toxin, an inhibitor of inhibitory guanine nucleotide-binding regulatory protein, suggesting the involvement of an inhibitory guanine nucleotide-binding regulatory protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered inflammatory responses in leukotriene-deficient mice

Leukotrienes have been implicated in the regulation of immune responses, including inflammation and immediate hypersensitivity reactions. Here, we describe the phenotypic analysis of leukotriene-deficient mice generated by inactivation of the 5-lipoxygenase (5LO) gene. These 5LO(-/-) mice were unable to synthesize detectable levels of leukotrienes and were more resistant to lethal anaphylaxis induced by platelet-activating factor. The intensity of an acute inflammatory response induced by arachidonic acid was similar in 5LO(-/-) mice and controls. However, the response in 5LO(-/-) mice, but not in controls, could be virtually eliminated by a cyclooxygenase inhibitor. These data suggest that inflammatory responses are modulated by arachidonic acid metabolites through a variety of interconnected mechanisms. This has important implications for understanding the early events of an inflammatory response and for designing drugs for use in therapeutic intervention.

Regulation of leukotriene biosynthesis

Leukotrienes are products of arachidonic acid metabolism derived through the action of the 5-lipoxygenase enzyme pathway. Leukotriene B4 has been implicated as a mediator of inflammation through induction of leukocyte and lymphocyte activation. The cysteinyl leukotrienes are important mediators of immediate hypersensitivity reactions and initiate smooth muscle contraction. Regulation of the production of leukotrienes can be achieved either through the action of direct 5-lipoxygenase inhibitors or indirect leukotriene biosynthesis inhibitors which bind to 5-lipoxygenase activating protein. Leukotriene C4 synthase and leukotriene A4 hydrolase represent alternative enzymic targets within the biosynthetic cascade. Leukotriene receptor antagonists also have important therapeutic possibilities and in particular, leukotriene D4 receptor antagonists have shown utility in the treatment of human bronchial asthma.

Tolfenamic acid and migraine--aspects on prostaglandins and leukotrienes

Migraine is a paroxysmal disorder characterized by recurrent attacks of headache, with or without associated visual and gastrointestinal disturbances. Migraine can be classified in two main groups, common and classic. Theories trying to explain the pathogenesis of a migraine attack may emphasize either the central or peripheral aspects of the disease. The vascular theory may stress the importance of either central or peripheral blood flow or both. Cerebral vasoconstriction in the early phases of the attack is followed by vasodilatation and pain. Biochemical mediators of vascular responses are not exactly known, but platelets and 5-hydroxytryptamine and thromboxane released from them as well as noradrenaline are potent vasoconstrictors, while kinins and prostaglandins can explain the vasodilatory phase of migraine attacks. This review presents evidence for the role of arachidonic acid metabolites, prostaglandins and leukotrienes in migraine. The evidence comes from the measurements of eicosanoids in biological fluids during and after the attack, infusion studies where vasodilatory prostaglandins mimic the migraneous symptoms, and the good effect of non-steroidal anti-inflammatory drugs in the treatment and prophylaxis of migraine attacks. Additional data are based on experimental biochemical studies in which catecholamines and indolamines have been shown to increase the synthesis of vasodilatory prostaglandins. However, the final evidence still awaits its confirmation.

Comparison of prostaglandin E1- and prostaglandin E2-induced hyperalgesia in the rat

We have studied prostaglandin E1-induced mechanical hyperalgesia in the rat hindpaw, by assessing paw-withdrawal thresholds, before and after injecting prostaglandin E1 alone or with other agents, in normal and streptozotocin-induced diabetic rats. In normal and diabetic rats, prostaglandin E1 (1-1000 ng) produced a dose-dependent decrease in mechanical nociceptive threshold. In diabetic rats, prostaglandin E1 was more potent than in normal rats, in producing hyperalgesia, whereas prostaglandin E2 hyperalgesia was not changed in normal and diabetic rats. Prostaglandin E1-induced hyperalgesia was not inhibited by E-type 1 prostaglandin receptor antagonists, SC19220 or SC51089, either in normal or diabetic rats. In fact, in the presence of SC19220, prostaglandin E1 produced enhanced hyperalgesia, in normal rats. Prostaglandin E1 hyperalgesia was not significantly modified by sympathectomy or indomethacin. Unlike prostaglandin E2, prostaglandin E1 hyperalgesia was not blocked by the inhibitor of the stimulatory guanine nucleotide-binding regulatory protein, guanosine 5'-O-(2-thiodiphosphate). It is suggested that prostaglandin E1 decreases primary afferent nociceptive threshold directly, by activating a prostaglandin receptor other than the E-type 1 prostaglandin receptor, and that this receptor is not coupled to a stimulatory guanine nucleotide-binding regulatory protein.

Neural form of voltage-dependent sodium current in human cultured dental pulp cells

Intradental, i.e. pulpal, cells may play an important part in sensory transduction in teeth, although the cellular mechanisms and the identity of the specific cell types involved are still unclear. Because the majority of cells in dental pulp are derived from neural crest, it seemed likely that these might have the membrane properties of other neural-derived cells found in the peripheral or central nervous system. The patch-clamp recording technique was used to show that cells in explant cultures from human dental pulp contain a voltage-gated, tetrodotoxin-sensitive inward current. Mean activation potential of the current was -42 +/- 2.5 mV and the voltage at half-inactivation was -79.4 +/- 5.3 mV, suggesting a neural-like sodium conductance. In addition, these cells were immunoreactive to glial acidic fibrillary protein, growth-associated protein (GAP-43), and vimentin, further suggesting that dental pulp contains a population of cells with membrane properties similar to neuronal satellite cells. These cells may contribute, either directly or indirectly, to somatosensation in teeth.

Identification of a B2 bradykinin receptor expressed by PC12 pheochromocytoma cells

We have used rat PC12 pheochromocytoma cells, a clonal cell line closely related to sympathetic neurons, to investigate reports that the bradykinin receptor expressed in the peripheral nervous system is distinct from the well-characterized B2 bradykinin receptor of smooth muscle. Although there have been reports that [Thi5,8,D-Phe7]bradykinin [where Thi is beta-(2-thienyl)alanine] is a full agonist at some sites in the peripheral nervous system, we find that in PC12 cells [Thi5,8,D-Phe7]bradykinin behaves as a competitive antagonist of bradykinin-stimulated phosphatidylinositol turnover. In particular, sufficient concentrations of [Thi5,8,D-Phe7]bradykinin completely block the increase in inositol bisphosphate and trisphosphate in response to 100 nM bradykinin; [Thi5,8,D-Phe7]bradykinin alone, at up to 10 microM, does not appreciably increase inositol bisphosphate and trisphosphate. In contrast to the absence of evidence for a distinctive neuronal receptor, we have found convincing evidence that the bradykinin receptor previously identified in smooth muscle is present in PC12 cells. Using the polymerase chain reaction, we have isolated a full-length cDNA encoding a bradykinin receptor that is expressed in PC12 cells and verified that its nucleotide sequence is identical except at a single position to that of the rat uterine B2 bradykinin receptor. When expressed in COS cells this uterine bradykinin receptor exhibits the same high affinity for [3H]bradykinin (Kd 4.4 nM), the same relative affinities for a series of kinin antagonists, and the same efficient coupling to phosphatidylinositol turnover (EC50 2.5 nM) as the receptor in PC12 cells. We interpret our data, and the findings of a number of pharmacological studies, as strengthening the view that the B2 receptor expressed in PC12 cells and in certain cells of the peripheral nervous system is identical to the receptor in rat uterine smooth muscle.