Identification of neuropeptide-degrading enzymes in the pancreas

Neutral endopeptidase (NEP) and aminopeptidase M (APM) were identified in the pancreas by enzymatic assays and Western blotting. The NEP activity, assessed by the phosphoramidon- and DL-thiorphan-inhibitable degradation of glutaryl-Ala-Ala-Phe-4-methoxy-2-naphthylamine, was 28.8 pmol/h/micrograms of pancreatic membrane protein and 124 pmol/h/10(6) pancreatic acinar cells. The APM enzymatic activity, assessed by the actinonin- and amastatin-inhibitable degradation of Ala-4-methoxy-2-naphthylamine, was 633 pmol/h/micrograms pancreatic membrane protein and 17.4 nmol/h/10(6) pancreatic acinar cells. Proteins corresponding to NEP (95 kDa) and APM (140 kDa) were identified in membranes by Western blotting. Both NEP and APM on acinar cells may degrade neuropeptides and regulate their effects on exocrine secretion.

Mediators of communication and adaptation in the neuroendocrine and immune systems

Bidirectional interactions between the immune and neuroendocrine systems influence specifically physiological activities as diverse as tissue localization of lymphocytes, antibody responses, hypothalamic-pituitary hormone secretion, and neural signal transmission. Our understanding of intersystem communications has been increased by the delineation of the innervation of immune organs, effects of neuromediators on immune cells, and neuroendocrine responses to individual immune cytokines. Two patterns of responses to neuroimmune mediators have been defined to distinguish between direct alterations in cellular function and the more complex states of differentiation and adaptation that condition the threshold and nature of reactions to subsequent stimuli. Recent identification of the molecular mechanisms of action of neuroimmune mediators is exemplified by elucidation of the requirement for prolactin in T lymphocyte proliferation and of the effects of vasoactive intestinal peptide on B lymphocyte expression of adherence proteins. Further knowledge of the advantages of multisystem integration of functions in host defense may reveal other novel mechanisms of cellular communication and biological adaptation.

Mouse monoclonal antibody to a latent epitope of leucocyte receptors for leukotriene B4

Human blood polymorphonuclear (PMN) leucocytes and human leucocytes of the HL-60 line, which were induced to differentiate by 1,25-dihydroxyvitamin D3, express stereospecific receptors for the potent chemotactic mediator, leukotriene B4 (LTB4), that is derived by 5-lipoxygenation from arachidonic acid. Monoclonal antibodies to LTB4 receptors (LTB4-R) were generated by immunizing BALB/c mice with partially purified PMN leucocyte membrane proteins, and fusing their splenocytes with P3X63Ag8 mouse myeloma cells. Hybridoma supernatants were screened initially by binding to PMN leucocyte LTB4-R protein, which had been affinity cross-linked with aminopropylamide (APA)-LTB4 and immobilized in plastic wells through attachment of the linked APA-LTB4 to adherent Fab of monoclonal anti-LTB4. Of the three clones producing antibodies which bound to LTB4-R, 0.5 mg/ml of one IgG3k antibody, termed E2, precipitated over 90% of the [3H]LTB4-binding activity of solubilized PMN leucocyte membrane proteins. E2 also bound to a radiolabelled protein of 70,000-80,000 MW from 125I-labelled PMN leucocyte membranes [35S]-labelled HL-60 cell membranes, and PMN leucocyte membranes affinity-labelled with [3H]APA-LTB4, that was identical in size to the LTB4-R precipitated by the rabbit IgG anti-idiotypic antibodies. E2 did not bind to intact PMN leucocytes or modify the binding of [3H]LTB4 by PMN leucocytes. The binding of E2 to LTB4-R in purified membranes of PMN leucocytes was less than one-fourth of that observed for the anti-idiotypic antibodies, but increased substantially after solubilization of the LTB4-R. The E2 monoclonal antibody thus recognizes a partially latent substituent of LTB4-R, which does not contribute to combining site function.

An acidic fibroblast growth factor protein generated by alternate splicing acts like an antagonist

Polymerase chain reaction amplification of cDNA for acidic fibroblast growth factor in several lines of cultured human cells revealed two forms of mRNA. The novel smaller mRNA lacks the entire second coding exon of the acidic fibroblast growth factor gene, whereas the previously identified mRNA consists of three coding exons. The truncated variant of acidic fibroblast growth factor (aFGF') is only 60 amino acids long with an apparent molecular mass of 6.7 kD on sodium dodecyl sulfate gels in contrast to 18 kD for the full-length acidic fibroblast growth factor. aFGF' elicits only minimal fibroblast proliferation and antagonizes the effects of acidic fibroblast growth factor when added exogenously to or when coexpressed with aFGF in BALB/c/3T3 fibroblasts. Thus, the truncated variant of acidic fibroblast growth factor may provide fibroblasts with a unique mechanism for endogenous regulation of their responses to acidic fibroblast growth factor.

Ligand-induced formation of the leukotriene B4 receptor-G protein complex of human polymorphonuclear leukocytes

The components of the polymorphonuclear leukocyte (PMNL) receptor for leukotriene B4 (LTB4) were examined by Sephacryl S-300 exclusion chromatography of PMNL membrane proteins, which were solubilized before and after the binding of [3H] LTB4. When the PMNL membranes were solubilized in 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) and filtered on Sephacryl S-300 prior to addition of [3H] LTB4, the binding activity was associated with a 65 kD protein. In contrast, the radioactivity of [3H] LTB4 bound to PMNL membranes prior to solubilization was recovered predominantly with a 140 kD protein. When PMNL membranes had been pretreated with pertussis toxin, but not cholera toxin, before the addition of LTB4 and subsequent solubilization, radioactivity was recovered predominantly with the 65 kD protein. The addition of guanylylimidodiphosphate (GMP-PNP), a nonhydrolyzable derivative of guanosine triphosphate (GTP), to PMNL membrane receptors bearing [3H] LTB4 either prior to or after CHAPS solubilization reduced the yield of the 140 kD presumed LTB4 receptor protein-G protein complex. That the maximum specific binding of [35S] guanosine-5'-0-3-thiotriphosphate (GTP-gammaS) to LTB4-binding proteins in the Sephacryl S-300 effluent corresponded to the 140 kD protein supported the presence of a G protein in the LTB4 receptor complex.

Eicosanoids, but not tachykinins, excite C-fiber endings in rat sciatic nerve-end neuromas

Normal nociceptors are sensitized by hyperalgesic mediators such as eicosanoids and tachykinins. The possibility that these mediators contribute to hyperalgesic pain associated with neural injury was investigated by examining their effects on the excitability of injured afferent nerve endings. In amounts that sensitize normal nociceptors and are hyperalgesic in normal skin, the eicosanoids prostaglandin I2 (PGI2), and 8(R),15(S)-dihydroxyicosatetraenoic acid (8(R),15(S)-diHETE) both excited some C-fibers in chronic neuromas of rat sciatic nerve. In contrast, the selective tachykinin-receptor agonists septide and senktide did not excite C-fibers. None of the mediators affected A-fibers. We conclude that PGI2 and 8(R),15(S)-diHETE may contribute to post-injury pain and hyperalgesia by an action on injured afferent endings.

Polymerase chain reaction amplification of messages for growth factors in cells from human bronchoalveolar lavage fluids

Genetic messages for polypeptide growth factors were assessed in human alveolar macrophages, obtained by bronchoalveolar lavage (BAL) from normal subjects (N = 3) and from patients with pneumonia (N = 3), pulmonary lymphoma (N = 3), and idiopathic pulmonary fibrosis (N = 3). Complementary DNAs (cDNAs) were prepared by reverse transcription of the RNA extracted from alveolar macrophages before and after culture on a plastic surface. The cDNAs encoding 10 different growth factors were amplified for electrophoretic analysis by polymerase chain reaction with a pair of 3' and 5' primers specific for each factor. Alveolar macrophages from all normal subjects and patients expressed the messages for interleukin-1 beta and transforming growth factor-beta. Alveolar macrophages from some normal subjects also contained message for insulin-like growth factor-1. Alveolar macrophages from six of nine patients with lung diseases also expressed messages for one or more additional growth factors, including epidermal growth factor, transforming growth factor-alpha, interleukin-1 alpha, and platelet-derived growth factor. The polymerase chain reaction technique thus permits determination of the profile of growth factors contributed to pulmonary reactions by alveolar macrophages, which may be important in pulmonary healing and fibrosis.

Down-regulation of receptor antigen in leukotriene B4-induced chemotactic deactivation of human polymorphonuclear leucocytes

Pretreatment of suspensions of human polymorphonuclear leucocytes (PMNL) with leukotriene B4 (LTB4) induces chemotactic deactivation, characterized by diminished expression of high-affinity LTB4 receptors and selectively decreased chemotactic responsiveness of the PMNL to LTB4. Rabbit anti-idiotypic antibodies (a-Id) to mouse monoclonal anti-LTB4, which bind to 60,000-80,000 molecular weight (MW) membrane protein of PMNL receptors for LTB4 in Western blots and block binding of [3H]LTB4 to high-affinity receptors of PMNL, detected a reduction in LTB4 receptor antigen during chemotactic deactivation. Loss of high-affinity receptors for LTB4 from the surface of PMNL deactivated by incubation with 10 nM LTB4 was significant after 1 min and after 20 min reached a mean maximum of 82% and 61%, respectively, as assessed by binding of [3H]LTB4 and a-Id. Inhibitors of PMNL proteases did not prevent the deactivation-induced decreases in surface receptors for LTB4. Disruption of deactivated PMNL and solubilization of membrane proteins failed to expose intracellular LTB4 receptors. Incubation of membranes isolated from PMNL with 100 nM LTB4 resulted in a loss of LTB4 receptors similar to that observed in intact PMNL. Changes in LTB4 receptor protein structure or membrane localization, rather than endocytosis or proteolysis, thus appear to explain the rapidly decreased expression of LTB4 receptors, which results from stimulus-specific deactivation.

Cloning and expression of the human vasoactive intestinal peptide receptor

Vasoactive intestinal peptide (VIP) is a neuroendocrine mediator found in the central and peripheral nervous system. Distinct subsets of neural, respiratory, gastrointestinal, and immune cells bear specific high-affinity receptors for VIP, which are associated with a guanine nucleotide-binding (G) protein capable of activating adenylate cyclase. A cDNA clone (GPRN1) encoding the human VIP receptor was identified in libraries prepared from the Nalm 6 line of leukemic pre-B lymphoblasts and the HT-29 line of colon carcinoma cells. The deduced 362-amino acid polypeptide sequence encoded by GPRN1 shares a seven-transmembrane-segment hydropathicity profile with other G protein-coupled receptors. Northern blot analyses identified a 2.7-kilobase transcript of the VIP receptor in Nalm 6 and HT-29 cells as well as in tissues from rat brain, colon, heart, lung, kidney, spleen, and small intestine. COS-6 cells transfected with GPRN1 bound 125I-labeled VIP specifically with a dissociation constant (Kd) of 2.5 nM. VIP--and less effectively secretin, peptide histidine isoleucine (PHI), and glucagon competitively displaced bound 125I-VIP from transfected COS-6 cells, with potencies in the order VIP greater than secretin = PHI much greater than glucagon. VIP stimulated adenylate cyclase activity in stably transfected Chinese hamster ovary K1 cells, inducing a 3-fold increase in the intracellular level of cAMP. When the antisense orientation of the VIP receptor clone was introduced into HT-29 cells, there was a 50% suppression of the specific binding of 125I-VIP and of the VIP-induced increase in cAMP level, relative to untransfected cells. The VIP receptor cloned exhibits less than or equal to 24% homology with other receptors in the same superfamily and thus represents a subset of G protein-coupled receptors for peptide ligands.

Affinity labeling of the membrane protein-binding component of human polymorphonuclear leukocyte receptors for leukotriene B4

A radiolabeled N-(3-aminopropyl)-leukotriene B4 amide ([3H]LTB4-APA) analog of the potent leukocyte chemotactic factor leukotriene B4 (LTB4) binds to receptors for LTB4 in plasma membrane-enriched preparations from human blood polymorphonuclear leukocytes (PMNL) and intact PMNL with respective mean dissociation constants of 2.3 nM and 69 nM at 4 degrees C. The [3H]LTB4-APA bound to plasma membrane-enriched preparations from PMNL was covalently cross-linked to membrane proteins with disuccinimidyl suberate. Solubilization and resolution by SDS-PAGE of proteins from [3H]LTB4-APA-labeled PMNL membranes revealed predominant labeling of a 60-kDa protein. Labeling of the PMNL membrane protein was inhibited by LTB4 and its analogs at concentrations similar to those inhibiting the binding of [3H]LTB4 to its receptor, with an identical rank order of potency of LTB4 greater than 20-hydroxy-LTB4 greater than LTB4-APA = 5(S),12(R)-dihydroxy-eicosa-14-cis-6,8,10-trans-tetraenoic acid much greater than LTD4 = LTC4. GTP suppressed the labeling of the 60-kDa PMNL membrane protein to an extent consistent with the decrease in receptor affinity for LTB4 induced by GTP. The stereospecificity of the affinity cross-linking reaction and the regulation by GTP support the identification of an approximately 60-kDa protein as the binding component of the PMNL receptor for LTB4.

Affinity labeling of the membrane protein-binding component of human polymorphonuclear leukocyte receptors for leukotriene B4

A radiolabeled N-(3-aminopropyl)-leukotriene B4 amide ([3H]LTB4-APA) analog of the potent leukocyte chemotactic factor leukotriene B4 (LTB4) binds to receptors for LTB4 in plasma membrane-enriched preparations from human blood polymorphonuclear leukocytes (PMNL) and intact PMNL with respective mean dissociation constants of 2.3 nM and 69 nM at 4 degrees C. The [3H]LTB4-APA bound to plasma membrane-enriched preparations from PMNL was covalently cross-linked to membrane proteins with disuccinimidyl suberate. Solubilization and resolution by SDS-PAGE of proteins from [3H]LTB4-APA-labeled PMNL membranes revealed predominant labeling of a 60-kDa protein. Labeling of the PMNL membrane protein was inhibited by LTB4 and its analogs at concentrations similar to those inhibiting the binding of [3H]LTB4 to its receptor, with an identical rank order of potency of LTB4 greater than 20-hydroxy-LTB4 greater than LTB4-APA = 5(S),12(R)-dihydroxy-eicosa-14-cis-6,8,10-trans-tetraenoic acid much greater than LTD4 = LTC4. GTP suppressed the labeling of the 60-kDa PMNL membrane protein to an extent consistent with the decrease in receptor affinity for LTB4 induced by GTP. The stereospecificity of the affinity cross-linking reaction and the regulation by GTP support the identification of an approximately 60-kDa protein as the binding component of the PMNL receptor for LTB4.

Chemotactic activity and receptor binding of neutrophil attractant/activation protein-1 (NAP-1) and structurally related host defense cytokines: interaction of NAP-2 with the NAP-1 receptor

Neutrophil attractant/activation protein-1 (NAP-1) has sequence similarity to platelet factor-4 (PF-4) and to NAP-2 (a truncated from of connective tissue activating protein-III [CTAP-III(des 1-15)]. We compared chemotactic activity for neutrophils of these related proteins. We also included for comparison CTAP-III, CTAP-III(des 1-13), the C-terminal dodecapeptide of PF-4 [PF-4(59-70)], and C5a. Chemotactic potency (EC50) was highest for NAP-1 and C5a. Although chemotactic efficacy (peak percentage of neutrophils migrating) was comparable for C5a, NAP-1, and NAP-2, the NAP-2 response occurred only at concentrations 100-fold higher than the NAP-1 EC50 of 10(8) M. Data for the CTAP-III proteins confirmed that CTAP-III is not an attractant and that chemotactic activity appears as a result of cleavage of residues at the N-terminus to make CTAP-III(des 1-13) or NAP-2 [CTAP-III(des 1-15)]. Chemotactic activity of PF-4 was low and variable, with no significant response by neutrophils from six of nine subjects. In contrast, PF-4(59-70) regularly induced high chemotactic responses, although the EC50 of 1.6 x 10(5)M was 1,000-fold greater than that of NAP-1. The binding of fluoresceinated NAP-1 to neutrophils was inhibited by unlabeled NAP-1 or NAP-2 but not by PF-4 or PF-4 (59-70). This suggests that NAP-2 interacts with the neutrophil NAP-1 receptor. Despite the low chemotactic potency of NAP-2, it is a potential attractant at sites of injury because of the relatively large amounts of the parent CTAP-III released from platelets, as indicated by a serum concentration of approximately 10(-6) M.

Isolation and partial characterization of the structures of fibroblast activating factor-related proteins from U937 cells

Human cultured monocyte-like tumour cells of the U937 histiocyte derived line were stimulated with phorbol myristate acetate, and generated and released an 18,000 MW polypeptide fibroblast-activating factor (FAF). Based on recognition by an antiserum to a synthetic peptide representing the 17 amino-terminal amino acids of FAF, two proteins of 32,000 and 35,000 MW were identified in extracts of U937 cells. Purification of the intracellular FAF-related proteins to homogeneity allowed the generation and amino acid sequencing of nine tryptic fragments of 4-11 amino acids. Neither of the intracellular FAF-related proteins exhibited the fibroblast proliferation-stimulating activity of FAF, suggesting that they are biosynthetic precursors analogous to the inactive propeptides of interleukin-1 beta and tumour necrosis factor-alpha.

Relative quantification of collagen mRNA in fibroblasts by a radioactive polymerase chain reaction technique

A radioactive polymerase chain reaction (PCR) method has been developed for the relative quantification of the human alpha-2 chain of type I collagen [hu alpha-2(I)] in cells. cDNAs generated by reverse transcription from the total pool of cytoplasmic RNA serve as a template for polymerase chain reaction amplification of a hu alpha-2(I) cDNA primed by two sequence-specific synthetic oligonucleotides. The distinctive 390 bp hu alpha-2(I) cDNA and two Aval fragments of 220 and 170 bp are identified by agarose gel electrophoresis. alpha-32P-dCTP of defined specific activity is included in the PCR reaction and the 390 bp cDNA is excised from the electrophoresis gel to permit direct radioactive quantification of hu alpha-2(I) mRNA. The amount of hu alpha-2(I) mRNA expressed in as few as 111 fibroblasts was determined reliably. In contrast, the hu alpha-2(I) mRNA from at least 5 x 10(5) fibroblasts was required for detection by Northern blot analysis developed with the same cDNA probe radiolabelled with alpha-32P-dCTP by random priming. Human bronchoalveolar lavage (BAL) fluids of six patients with fibrosing lung diseases stimulated the level of expression of hu alpha-2(I) mRNA in cultured human fibroblasts as determined by this technique. The radioactive PCR method thus quantifies hu alpha-2(I) mRNA in fibroblasts with sufficient sensitivity to study fibroblast activation in vitro and detect fibroblast stimuli in human clinical samples.

Elevated serum concentrations of IgE antibodies to environmental antigens in HIV-seropositive male homosexuals

Forty-five homosexual male subjects with human immunodeficiency virus (HIV) infection, who received care during a 4-month period in an ambulatory center for acquired immunodeficiency syndrome (AIDS), were classified according to their principal presentation with characteristic secondary infections (CDC group IV C, N = 28), cancers (IV D, N = 10), or limited or no symptoms (groups II, III, IV A, or IV B, N = 7). The incidence of allergic rhinitis and conjunctivitis increased after HIV seroconversion by approximately twofold in patients of groups IV C and IV D. The mean serum concentration of IgE was significantly higher for group IV C than for the other HIV-seropositive groups and for a control group of 45 HIV-seronegative homosexual male subjects from the same community who were studied concurrently. More patients in groups IV C and IV D had positive RASTs for a panel of environmental antigens than patients in the other HIV-seropositive groups and the HIV-seronegative control group. Patients with AIDS presenting with typical secondary infections thus have a high frequency of some clinical and laboratory manifestations of allergic diseases.

Neuropeptides, mast cells and allergy: novel mechanisms and therapeutic possibilities

Diverse neuropeptides are released by neuroendocrine and immune cells at the sites of allergic and inflammatory reactions. The neuropeptides and other neuromediators affect functions of smooth muscle, microvasculature and secretory cells, and are potent stimuli of mast cell, lymphocyte and other leucocyte contributions to such reactions. The distinctive immune sources, structures and cellular receptors for neuromediators suggest the possibility of novel pathogenetic mechanisms and levels of pharmacological intervention specific for neuroregulation of immunity and hypersensitivity.

Mediation of prolonged increases in nasal mucosal blood flow by calcitonin gene-related peptide (CGRP)

Calcitonin gene-related peptide (CGRP) is a vasoactive and smooth muscle contractile neuropeptide, which is released during human nasal allergic reactions. Mean values for nasal blood flow (NBF), quantified in each nostril by a laser Doppler technique, varied no more than +/- 25% of a mean initial reading in normal human subjects over 4 hr in a controlled environment. Intranasal administration of multiple doses of CGRP to 17 normal subjects stimulated significant mean increases in NBF at 30-1000 ng of CGRP, with maximal mean rises of 86-130% after 100 and 300 ng of CGRP. Delivery of incremental doses of CGRP every 30 min for 2 hr evoked repetitive responses without tachyphylaxis. A single vasoactive dose of CGRP, which achieved nasal fluid concentrations similar to those elicited by antigen challenge, elicited the sensation of nasal obstruction in most subjects at 1 hr and for up to 4 hr after CGRP, without elevating nasal fluid concentrations of histamine. CGRP thus is a potent histamine-independent mediator of allergic reactions.

Elevated synovial tissue concentration of the common acute lymphoblastic leukaemia antigen (CALLA)-associated neutral endopeptidase (3.4.24.11) in human chronic arthritis

The cell-surface neutral endopeptidase 3.4.24.11 (NEP) activity of the common acute lymphoblastic leukaemia antigen (CALLA) cleaves diverse peptide mediators at specific sites and it has been postulated that it regulates immune responses. The concentration of NEP was quantified in detergent extracts of synovial tissues by the percentage hydrolysis of [3H-D-Ala]-Leu enkephalin/hr/100 mg of tissue. The synovial tissue concentration of NEP was higher in all patients with rheumatoid arthritis (n = 7; group mean +/- SD = 29.4 +/- 20.2%), and was higher with degenerative joint disease (n = 6 of 8; group mean +/- SD = 11.9 +/- 10.4%) than with traumatic arthropathy (n = 3; 1.1 +/- 0.7%). The lack of direct relationship between synovial tissue NEP concentration and leukocytic infiltration suggests that the cellular source of NEP may be synoviocytes or fibroblasts, and that NEP may have distinctive pathogenetic roles in human arthritis.

The 15-lipoxygenase product, 8R,15S-diHETE, stereospecifically sensitizes C-fiber mechanoheat nociceptors in hairy skin of rat

1. This study examined the effects of the 15-lipoxygenase product of arachidonic acid metabolism, (8R,15S)-dihydroxyicosa-(5E-9,11,13Z)tetraenoic acid (8R,15S-diHETE), on mechanical thresholds and thermal responses of saphenous nerve cutaneous C-fiber nociceptors that innervate the hairy skin of the rat hindpaw. Single C-fiber mechanoheat nociceptors (C-MH) that had von Frey hair (VFH) thresholds greater than 5 g and were activated by a noxious heat stimulus were chosen for study. We also studied the effects of prostaglandin E2 (PGE2), a cyclooxygenase product of arachidonic acid metabolism, on these nociceptors. 2. The 63 C-MHs studied had a conduction velocity of 0.82 +/- 0.03 m/s (mean +/- SE) and a mechanical threshold of 13.4 +/- 2.4 g. In a subgroup of these (n = 24), the thermal threshold was measured as (44 +/- 1 degree C) (mean +/- SE). 3. 8R,15S-diHETE produced a significant decrease in mechanical threshold of C-MHs (n = 33). The 8R,15S-diHETE-induced sensitization of C-MHs to mechanical stimuli was completely antagonized by coadministration with a stereoisomer, 8S,15S-diHETE (n = 10). 4. The mechanical threshold of C-MHs (n = 10), previously injected with the combination of 8R,15S-diHETE and 8S,15S-diHETE, was significantly reduced by a subsequent injection of PGE2. In a separate group of C-MHs (n = 7), PGE2 was co-injected with 8S,15S-diHETE, which failed to antagonize the sensitizing effect of PGE2 on mechanical threshold. 5. 8R,15S-diHETE also sensitized C-MHs (n = 9) to a thermal stimulus consisting of 37 degrees C for 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression by ingested eicosapentaenoic acid of the increases in nasal mucosal blood flow and eosinophilia of ryegrass-allergic reactions

Nasal mucosal blood flow, assessed by a laser Doppler probe technique, and the concentration of eosinophils in nasal secretions were quantified during challenge of one nostril with ryegrass-pollen antigen and the other nostril with diluent alone in seven patients with ryegrass-allergic rhinitis. The identical studies were repeated after an 8-week course of 3.5 gm/day of eicosapentaenoic acid (EPA). Ryegrass antigen evoked mean rises in nasal blood flow of 30% to 100% after 10 and 30 minutes that were significant, relative to prechallenge levels and to levels after diluent challenge, both before and after EPA. Antigen-induced increases in nasal blood flow were significantly less after than before EPA at 10 minutes, and at 180 minutes increases were significant only before EPA. In ryegrass-allergic patients with rhinitis who did not take EPA between the two studies, the increases in blood flow after antigen challenge were the same on both occasions. Similarly, the nasal eosinophilia elicited by antigen was significant at 180 minutes only before EPA. Both a composite index of signs and symptoms and the constituent variables, reflecting the clinical response to antigen challenge, were unaffected by EPA. The suppression by EPA of responses of nasal blood flow and nasal eosinophils to antigen challenge supports a role for fatty acid and phospholipid mediators in allergic rhinitis, but the clinical assessment did not provide evidence for any symptomatic benefit from EPA.

Diverse responses of human fibroblasts to a highly purified fibroblast-activating factor from the U937 line of human monocytes

The responses of human dermal fibroblasts to highly purified fibroblast-activating factor (FAF), derived from supernatants of U937 human monocytes stimulated with phorbol myristate acetate (PMA), were investigated with several in vitro assays of specific synthetic functions. The highly purified peptide was detected as a single 16,000-18,000 MW protein, by both silver staining and Western blot analysis, with an antiserum generated against a synthetic peptide representing the amino-terminal sequence of 17 amino acids. At concentrations that induced similar levels of fibroblast proliferation, transforming growth factor-beta (TGF-beta), interleukin-1 (IL-1), acidic fibroblast growth factor (aFGF) and FAF also stimulated fibroblasts to generate and release prostaglandin E2 (PGE2) and proteoglycans. TGF-beta had the least effect on proteoglycan production. In contrast, the production and secretion of collagen evoked by FAF was only minimal when compared to that observed with IL-1 and aFGF. FAF and aFGF promoted fibroblast-induced collagen gel contraction with similar potency. Thus, the profile of fibroblast effects is a specific property of each cytokine.

Unique pattern of cleavage of vasoactive intestinal peptide by human lymphocytes

Human cultured T lymphocytes of the Jurkat line and myeloma cells of the U266 line cleaved the 28 amino acid vasoactive intestinal peptide (VIP1-28) preferentially at three sites with time- and temperature-dependence. The fragments VIP4-28 and VIP23-28) from an endopeptidase activity, and VIP15-28 from a trypsin-like peptidase, together represented a range of 26-65% of the VIP1-28 recovered after 2 hr at 37 degrees C or 4 hr at 22 degrees C, based on the absorbance of purified peptides and the radioactivity of [125I]Tyr10 VIP1-28. The endopeptidase activity was associated with membranes recovered after disruption of U266 cells by nitrogen cavitation. Pretreatment of intact U266 and Jurkat cells with diisopropylfluorophosphate (DFP) and the subsequently isolated subcellular particles with phenylmethylsulphonylfluoride (PMSF) and leupeptin inhibited the trypsin-like enzyme by a mean of 80%, without suppressing endopeptidase activity. In contrast, 0.1 mM DL-thiorphan and phosphoramidon blocked selectively a range of 35-70% of the endopeptidase activity in membrane preparations and intact cells. The capacity of lymphocytes to degrade VIP1-28 may substantially alter the effects of this neuromediator on functions of some subsets of T and B cells.

High-affinity receptors for vasoactive intestinal peptide on human myeloma cells

Cultured human myeloma cells of the U266 line and leukemic T cells of the Jurkat line bound synthetic [125I]Tyr10-vasoactive intestinal peptide1-28 ([125I]VIP1-28) specifically and with an affinity similar to that of neuroendocrine cells. Specific binding reached equilibrium after 2 h at 22 degrees C for both myeloma cells and T cells, attained a maximum of 57 to 71% of total binding, and was reversed in 1.5 to 3 h by an excess of non-radioactive VIP1-28. Analyses of the ligand concentration-dependence of binding of the ligand concentration-dependence of binding of [125I]VIP1-28 revealed a mean Kd of 7.6 nM for a mean of 41,207 receptors per myeloma cell and 5.2 nM for 12,266 receptors per T cell. The relative affinity of binding of mast cell-derived VIP10-28 free acid and synthetic analogues suggested differences in specificity between lymphocyte and neuroendocrine receptors. Distinct sets of receptors thus appear to mediate the effects of VIP on functions of both antibody-producing cells and T cells.

High-affinity receptors for vasoactive intestinal peptide on human myeloma cells

Cultured human myeloma cells of the U266 line and leukemic T cells of the Jurkat line bound synthetic [125I]Tyr10-vasoactive intestinal peptide1-28 ([125I]VIP1-28) specifically and with an affinity similar to that of neuroendocrine cells. Specific binding reached equilibrium after 2 h at 22 degrees C for both myeloma cells and T cells, attained a maximum of 57 to 71% of total binding, and was reversed in 1.5 to 3 h by an excess of non-radioactive VIP1-28. Analyses of the ligand concentration-dependence of binding of the ligand concentration-dependence of binding of [125I]VIP1-28 revealed a mean Kd of 7.6 nM for a mean of 41,207 receptors per myeloma cell and 5.2 nM for 12,266 receptors per T cell. The relative affinity of binding of mast cell-derived VIP10-28 free acid and synthetic analogues suggested differences in specificity between lymphocyte and neuroendocrine receptors. Distinct sets of receptors thus appear to mediate the effects of VIP on functions of both antibody-producing cells and T cells.

Appearance of neuropeptides in ascitic fluid after peritoneal therapy with interleukin-2 and lymphokine-activated killer cells for intraabdominal malignancy

Administration of intravenous interleukin-2 (IL-2), followed by intraperitoneal IL-2 and autologous lymphokine-activated killer (LAK) cells to six patients with colonic, ovarian, or endometrial carcinoma restricted to peritoneal spread increased significantly the ascitic fluid concentrations of the neuropeptides substance P (SP) and calcitonin-gene related peptide (CGRP). After intravenous IL-2 alone, the level of SP rose 10- to 140-fold, without a change in that of CGRP. Intraperitoneal IL-2 and LAK cells led to elevations in the concentrations of SP and CGRP to respective maximal means of 319 and 175 pM after 8 hr, which were maintained for 24-48 hr without alterations in the levels of vasoactive intestinal peptide or somatostatin. SP and CGRP from peritoneal fluid were chromatographically indistinguishable from synthetic neuropeptides. The increases in concentrations of SP and CGRP after IL-2 and LAK-cell therapy are the first demonstration of a neural response to a human cellular immunological reaction. The time course and magnitude of the neuropeptide response suggest a role in the vascular side effects of this form of treatment.

Late appearance of phospholipid platelet-activating factor and leukotriene B4 in human skin after repeated antigen challenge

Inflammatory mediators were assessed in supernatants of chamber fluids from eight ragweed- or grass-sensitive subjects during antigen-induced cutaneous inflammatory responses. Platelet activating factor (PAF) accumulated at concentrations of 1 pm to 90 mumol/L in six of eight subjects beginning at 3 hours and continuing for 9 hours after antigen challenge. Leukotriene B4 (LTB4) was detectable at cutaneous sites of antigen challenge in five of five subjects throughout the 9-hour period at levels from 1 to 36 nmol, a range of 38% to 80% of which were omega-oxidation metabolites. Histamine levels peaked in the first hour at 106 +/- 18 ng/ml and decreased to a plateau of 11 to 13 ng/ml at 3 to 9 hours after antigen challenge. No PAF and only very low levels of LTB4 (0.1 to 1.3 nmol) and of histamine (less than 2 ng/ml) were detected at buffer-control sites during the 9 hours of study. Continuous antigen exposure thus results in the persistent release of histamine and LTB4 and the late appearance of PAF, all of which may contribute to the chronicity of allergic disorders and may have a bearing on the IgE-mediated, late-phase cutaneous response.

Preferential cleavage of amino- and carboxyl-terminal oligopeptides from vasoactive intestinal polypeptide by human recombinant enkephalinase (neutral endopeptidase, EC 3.4.24.11)

Human recombinant enkephalinase (neutral endopeptidase, EC 3.4.24.11) cleaved synthetic vasoactive intestinal peptide (VIP1-28) with time-and peptidase concentration-dependence, which left less than 30% intact after 30 micrograms was incubated at 37 degrees C with 0.1 micrograms and 10 micrograms of peptidase for 120 min and 15 min, respectively. The rank order of relative rates of peptidolysis amino-terminal to hydrophobic amino acids was Ala4 and Val5 greater than Tyr22 and Ile26 much greater than Leu13 and Met17. The many effects of VIP1-28 on epithelial cell and leukocyte functions thus may be influenced by degradation of the mediator by enkephalinase at the surface of target cells.

Distinct subsets of somatostatin receptors on cultured human lymphocytes

Somatostatin (SOM) is a neuroendocrine tetradecapeptide that suppresses specific functions of differentiated T-cells and antibody-producing cells. The Jurkat line of human leukemic T-cells and U266 IgE-producing human myeloma cells bound [I-Tyr11]SOM specifically. The maximal level of specific binding was attained by 1-2 h at 22 degrees C for both types of cells and reversed by 70-85% within 2-3 h after the addition of excess nonradioactive SOM. Computer-assisted Scatchard analysis of the competition curves revealed two classes of binding sites for both cells. An average of 144 and 1295 high affinity receptors per Jurkat and U266 cells had a Kd value of 3 pM and 5 pM, respectively, whereas a large number of low affinity sites had Kd values of 66 nM and 100 nM. The affinity of the analogs somatostatin 28, [I-Tyr11]SOM, and [D-Trp8, D-Cys14]SOM for Jurkat and U266 cell lines, relative to SOM, suggested a degree of specificity similar to receptors on neuroendocrine cells.

Identification of leukotriene B4 as the neutrophil chemotactic factor released by antigen challenge from passively sensitized guinea pig lungs

Neutrophils are prominent in some IgE-mediated allergic reactions and may contribute to the pathophysiology of immediate hypersensitivity. Antigen challenge of fragments of guinea pig lung tissue that were passively sensitized with IgE or IgG antibody evoked the release of neutrophil chemotactic activity (NCA) in parallel with histamine. The NCA released from lung tissue by both IgG- and IgE-dependent stimulation coeluted from a column of Sephacryl S-300 with synthetic leukotriene B4 (LTB4). The NCA in eluates from the Sephacryl S-300 column contained LTB4, as determined by high-performance liquid chromatography and specific radioimmunoassay, in quantities that accounted for the observed chemoattractant activity in the eluates. Furthermore, the NCA of supernatants from antigen-challenged lung fragments was reduced by a mean of 80% after absorption with a monoclonal antibody to LTB4. LTB4 thus constitutes the major functional constituent of NCA released after anaphylactic challenge of IgE- and IgG-sensitized guinea pig lung tissue.

Mediation of primary afferent peripheral hyperalgesia by the cAMP second messenger system

Cyclooxygenase (prostaglandin E2 and prostaglandin I2) and lipoxygenase [8(R), 15(S)-dihydroxyicosa-(5E-9,11,13Z)-tetraenoic acid] products of arachidonic acid metabolism are thought to produce peripheral hyperalgesia by a direct action on the primary afferent nociceptor. In this study we investigated the possibility that these eicosanoids generate hyperalgesia through a common second messenger in the rat. We report that 8-bromo cAMP, a membrane permeable analogue of cAMP, produces a dose-dependent hyperalgesia that is not affected by treatments that interrupt indirect routes of hyperalgesia production including sympathectomy with 6-hydroxydopamine, depletion of polymorphonuclear leukocytes (a source of hyperalgesic eicosanoids) with hydroxyurea, or blockade of the cyclooxygenase pathway of arachidonic acid metabolism with indomethacin. The phosphodiesterase inhibitor isobutyl-methylxanthine markedly prolongs the hyperalgesic effect of 8-bromo cAMP as well as those of the directly acting hyperalgesic agents prostaglandin E2, prostaglandin I2 and 8(R),15(S)-dihydroxyicosa-(5E-9,11,13Z)-tetraenoic acid. We conclude that the effect of all known hyperalgesic eicosanoids is mediated by the cAMP second messenger system and suggest, therefore, that cAMP mediates peripheral hyperalgesia in primary afferent nociceptors.

Enzymatic properties of the 15-lipoxygenase of human cultured keratinocytes

The arachidonic acid 15-lipoxygenase or linoleic acid omega-6 lipoxygenase of human neonatal foreskin cultured keratinocytes converts arachidonic acid to 15-hydroxy-eicosatetraenoic acid and linoleic acid to 13-hydroxy-linoleic acid. A mean of 93% of the 15-lipoxygenase activity in sonicates of cultured keratinocytes was recovered in the 400,000 X g supernatant, attesting to the cytosolic localization of this enzyme. Optimal 15-lipoxygenase activity in the 400,000 X g supernatant was expressed at pH 6.7-7.3 and in the presence of calcium at a concentration of 2 mM or higher. Keratinocyte 15-lipoxygenase metabolized arachidonic acid (Km = 10.6 microM) and linoleic acid (Km = 9.5 microM) with similar efficiency. Nordihydroguaiaretic acid and 5,8,11,14-eicosatetraynoic acid both inhibited the conversion of arachidonic acid to 15-HETE with respective 50% inhibitory concentrations of 2.0 microM and 0.9 microM, while ATP, GTP, and cyclic AMP had no effect on activity at pH 6.8-7.2. The enzymatic properties of human keratinocyte 15-lipoxygenase thus resemble those of PMN leukocyte 15-lipoxygenase and the mediators generated may contribute to the regulation of cutaneous sensation and inflammation.

Isolation and partial characterization of a fibroblast-activating factor generated by U-937 human monocytic leukocytes

Human cultured monocyte-like tumor cells of the U-937 line, that are incubated for 24 h at 37 degrees C with 100 ng/ml of PMA, generate and release a fibroblast-activating factor (FAF) capable of enhancing the uptake of [3H]TdR by human dermal fibroblasts in vitro. The predominant FAF activity in unpurified supernatants from U-937 cells was associated with one protein of 16 to 18 kDa, as assessed by SDS-PAGE and pI 4 to 5, as determined by IEF in gel. Isolation of the FAF in 15-liter batches of supernatant from cultures of 1.5 x 10(10) PMA-stimulated U-937 cells by ammonium sulfate precipitation and sequential filtration on Sephadex G-50, anion exchange chromatography, and reversed phase HPLC yielded microgram quantities of a homogeneous protein of sufficient purity for structural studies. Purified FAF was not absorbed by affinity columns bearing antisera to IL-1 beta, TNF or basic fibroblast growth factor die not share any tryptic peptides with IL-1 alpha or acidic fibroblast growth factor when analyzed by two-dimensional electrophoresis/chromatography on cellulose thin-layer plates, and has an amino-terminal sequence of amino acids that is different from any known fibroblast growth factor. FAF thus represents a unique human monocyte-derived protein that selectively stimulates human fibroblast proliferation and other functions.

Isolation and partial characterization of a fibroblast-activating factor generated by U-937 human monocytic leukocytes

Human cultured monocyte-like tumor cells of the U-937 line, that are incubated for 24 h at 37 degrees C with 100 ng/ml of PMA, generate and release a fibroblast-activating factor (FAF) capable of enhancing the uptake of [3H]TdR by human dermal fibroblasts in vitro. The predominant FAF activity in unpurified supernatants from U-937 cells was associated with one protein of 16 to 18 kDa, as assessed by SDS-PAGE and pI 4 to 5, as determined by IEF in gel. Isolation of the FAF in 15-liter batches of supernatant from cultures of 1.5 x 10(10) PMA-stimulated U-937 cells by ammonium sulfate precipitation and sequential filtration on Sephadex G-50, anion exchange chromatography, and reversed phase HPLC yielded microgram quantities of a homogeneous protein of sufficient purity for structural studies. Purified FAF was not absorbed by affinity columns bearing antisera to IL-1 beta, TNF or basic fibroblast growth factor die not share any tryptic peptides with IL-1 alpha or acidic fibroblast growth factor when analyzed by two-dimensional electrophoresis/chromatography on cellulose thin-layer plates, and has an amino-terminal sequence of amino acids that is different from any known fibroblast growth factor. FAF thus represents a unique human monocyte-derived protein that selectively stimulates human fibroblast proliferation and other functions.

Leukotriene B4 decreases the mechanical and thermal thresholds of C-fiber nociceptors in the hairy skin of the rat

1. We have recently shown that leukotriene B4 (LTB4), a product of the 5-lipoxygenase pathway of arachidonic acid metabolism, sensitizes nociceptors to mechanical stimuli. The present study examined whether LTB4 also induces a heat sensitization of cutaneous C-fiber nociceptors. The C-fiber nociceptors studied had von Frey hair thresholds greater than 5 g and were characterized according to their responses to noxious heat and chemical stimuli, including glacial acetic acid, bradykinin, and capsaicin. Thirty-four of the C-fibers that were activated by intense thermal stimulation were also activated by topical application of glacial acetic acid. They were classified as C-polymodal nociceptors (2, 28). Those that were activated by intense mechanical and thermal stimulation, but were unresponsive to acid, were classified as C-mechanoheat nociceptors (27). 2. Ninety-four percent of C-polymodal nociceptors and 60% of C-mechanoheat nociceptors were sensitized by LTB4. All C-fiber nociceptors that showed a decrease of their heat threshold also had a decrease of their mechanical threshold. LTB4 (75 ng) lowered the average heat threshold from 45 degrees C to 35 degrees C and produced an average decrease in the mechanical threshold of 86%. 3. The magnitude of the LTB4-evoked decrease in thermal threshold was similar to that produced by 75 ng of prostaglandin E2 (PGE2). These data demonstrate that LTB4 sensitizes C-mechanoheat nociceptors to both mechanical and thermal stimuli. 4. We conclude that LTB4 may contribute to the component of hyperalgesia that is resistant to nonsteroidal anti-inflammatory agents.

Leukotriene D4-induced increases in the cytoplasmic pH of human myelocytic leukocytes

The effects of leukotriene D4 on the intracellular pH of human myelocytes, derived from cultured HL-60 cells by dimethylsulfoxide-induced differentiation, were quantified with the fluorescent indicator 2',7'-bis-(2-carboxy-ethyl)-5,6-carboxyfluorescein. Leukotriene D4, but not C4 or E4, increased intracellular pH optimally by 3 min with a half-maximal effect at 1-2 nM. The increases in intracellular pH stimulated by leukotriene D4 were prevented by pretreatment of myelocytes with leukotriene D4 but not peptide chemotactic factors. Analogs of amiloride that inhibit selectively the Na+/H+ antiport also prevented the intracellular alkalinization induced by leukotriene D4. The rate of recovery of intracellular pH after an acid load with 30 mM sodium propionate was approximately 30% higher at each level of intracellular pH for myelocytes exposed to leukotriene D4 than for those challenged in buffer alone. The increase elicited by leukotriene D4 in the adherence of myelocytic leukocytes to surfaces thus is associated with an enhanced sensitivity of the Na+/H+ antiport to intracellular pH, that is, not coupled to an earlier rise in the cytosolic level of Ca+2.

Structurally distinctive vasoactive intestinal peptides from rat basophilic leukemia cells

Peptides recognized by rabbit antibodies to vasoactive intestinal peptide (VIP) were extracted from diisopropyl fluorophosphate-treated rat basophilic leukemia (RBL) cells and resolved by filtration on Sephadex G-25 in 50 mM acetic acid. The immunoreactive VIPs of RBL cells eluted from Sephadex G-25 at 35-41%, 53-60%, and 69-73% bed volume, but not at 63-68% as for the neuropeptide VIP1-28. The two forms of immunoreactive VIP larger than VIP1-28 reacted with antibodies to both VIP1-9 and VIP10-28, but the smallest was bound only by antibodies to VIP10-28. The smallest immunoreactive VIP was purified by ion-exchange and reverse-phase high-performance liquid chromatography, and the amino acid sequence was determined to be that of VIP10-28 with asparagine-free acid at the carboxyl terminus rather than the amide of VIP neuropeptide. Challenge of RBL cells with 1 microM ionophore A23187 at 37 degrees C released VIP10-28 rapidly to a mean of 75% at 5 min and 77% at 30 min. The VIP generated and released by mast cells thus consists of a mixture of peptides that all differ structurally from the neuropeptide VIP.

Sulfidopeptide-leukotriene peptidases in pulmonary edema fluid from patients with the adult respiratory distress syndrome

The human pulmonary edema fluid concentrations of LTC4 and of LTD4 and LTE4, derived peptidolytically from LTC4, were assessed by radioimmunoassays of the mediators resolved by reverse-phase high-performance liquid chromatography. The mean pulmonary edema fluid concentration (+/- SD) of LTD4 of 19.2 +/- 25.6 nM for 12 patients with the adult respiratory distress syndrome and of LTE4 of 192 +/- 309 nM for 10 of the patients were significantly higher (P less than 0.005 and P less than 0.05) than those of 2.2 +/- 2.4 and 11.0 +/- 18.2 nM, respectively, for 10 patients with cardiogenic pulmonary edema, whereas the lower mean concentrations of LTC4 were not significantly different for the two groups. Pulmonary edema fluid from five patients with adult respiratory distress syndrome, one with cardiogenic pulmonary edema, and one with an indeterminate syndrome contained similar concentrations of peptidoleukotriene peptidases. The LTC4 and LTD4 peptidolytic activities in ARDS fluids were 81 and 142 kD, respectively, by gel filtration. The extents of peptidolysis of [3]LTC4 and [3]LTD4 by 100 microliter of pulmonary edema fluid attained respective mean maximum levels of 74.5 +/- 2.9% (N = 5) and 37.7 +/- 10.2% (N = 4) after 30 min at 37 degrees C and were inhibited by serine-borate and by cysteine, respectively. The predominance of LTD4 and LTE4 over LTC4 in states of altered pulmonary vascular pressure and permeability thus is attributable to two distinct peptidases.

Selective modulation by guanine nucleotides of the high affinity subset of plasma membrane receptors for leukotriene B4 on human polymorphonuclear leukocytes

Isolated human polymorphonuclear (PMN) leukocyte plasma membranes express high affinity (mean Kd = 0.12 nM) and low affinity (mean Kd = 50 nM) receptors for the chemotactic factor leukotriene B4 (5(S),12(R)-dihydroxy-eicosa-6,14 cis-8,10 trans-tetraenoic acid; LTB4) that are similar to those on intact PMN leukocytes. A portion of high affinity LTB4-R on PMN leukocyte membranes were converted to the low affinity state by GTP (mean +/- SE = 28.6 +/- 14.0%) and nonhydrolyzable GTP analogues, such as 5'-guanylylimidodiphosphate (GMP-PNP), in a concentration-dependent, nucleotide-specific, and reversible manner, without altering the intrinsic binding affinities of either class. [3H]GMP-PNP bound specifically to one class of receptors (mean Kd = 13 nM) on PMN leukocyte membranes. The interdependence of the LTB4-binding membrane protein and guanine nucleotide-binding protein was suggested by the capacity of LTB4 to enhance by a maximum of 150% the binding of [3H]GMP-PNP to PMN leukocyte membranes by increasing the number, but not altering the affinity, of receptors for GMP-PNP. Pertussis toxin, but not cholera toxin, reversed the enhancement of binding of [3H]GMP-PNP produced by LTB4. Guanine nucleotide-binding proteins and high affinity LTB4-R thus exhibit a mutual regulation that differs mechanistically from that of peptide chemotactic factor receptors on PMN leukocytes.

Selective modulation by guanine nucleotides of the high affinity subset of plasma membrane receptors for leukotriene B4 on human polymorphonuclear leukocytes

Isolated human polymorphonuclear (PMN) leukocyte plasma membranes express high affinity (mean Kd = 0.12 nM) and low affinity (mean Kd = 50 nM) receptors for the chemotactic factor leukotriene B4 (5(S),12(R)-dihydroxy-eicosa-6,14 cis-8,10 trans-tetraenoic acid; LTB4) that are similar to those on intact PMN leukocytes. A portion of high affinity LTB4-R on PMN leukocyte membranes were converted to the low affinity state by GTP (mean +/- SE = 28.6 +/- 14.0%) and nonhydrolyzable GTP analogues, such as 5'-guanylylimidodiphosphate (GMP-PNP), in a concentration-dependent, nucleotide-specific, and reversible manner, without altering the intrinsic binding affinities of either class. [3H]GMP-PNP bound specifically to one class of receptors (mean Kd = 13 nM) on PMN leukocyte membranes. The interdependence of the LTB4-binding membrane protein and guanine nucleotide-binding protein was suggested by the capacity of LTB4 to enhance by a maximum of 150% the binding of [3H]GMP-PNP to PMN leukocyte membranes by increasing the number, but not altering the affinity, of receptors for GMP-PNP. Pertussis toxin, but not cholera toxin, reversed the enhancement of binding of [3H]GMP-PNP produced by LTB4. Guanine nucleotide-binding proteins and high affinity LTB4-R thus exhibit a mutual regulation that differs mechanistically from that of peptide chemotactic factor receptors on PMN leukocytes.

Generation and recognition of leukotriene mediators of hypersensitivity and inflammation

The potent mediators generated by the 5- and 15-lipoxygenation of arachidonic acid have diverse effects on smooth muscles, blood vessels, leukocytes, epithelial cells and glands, and sensory neurons, which suggest possible roles in the initiation and regulation of physiological and biochemical events. The responses to leukotrienes and related mediators are attributable to binding by stereospecific cellular receptors and consequent activation of biochemical transductional sequences analogous to those characteristic of other receptor systems. The elevated concentrations of these mediators in lesional fluids and tissues of inflammatory bowel disease and other hypersensitivity and inflammatory states are, in some instances, clearly related to the time course of development of the disease process. Systematic application of specific inhibitors and antagonists that are becoming available will define more clearly the involvement of leukotrienes in health and disease and possibly lead to new therapeutic approaches.

Effect of eicosapentaenoic acid in asthma

The role of arachidonic acid metabolites in the pathogenesis of airway inflammation and clinical asthma is currently unknown. The addition of eicosapentaenoic acid (EPA) to the diet of humans has been shown to generate metabolites that are less potent than their arachidonic acid counterparts. The substitution of EPA for arachidonic acid metabolites in patients might cause a decrease in airway inflammation and an improvement in clinical asthma. We studied the effect of addition of EPA to the diet of twelve asthmatic patients. Standard clinical evaluations and pulmonary function tests were done on weeks 0, 3, 6, 10, 12 and 14. Patients ingested either low-dose EPA (0.1 g/day) or high-dose EPA (4.0 g/day) from weeks 6-14 (total of 8 weeks). There was no difference in clinical status or pulmonary function between groups at the start of the study. There was no change in clinical status or pulmonary function between or within groups at the end of 8 weeks of EPA ingestion.

Distinctive patterns of release of neuroendocrine peptides after nasal challenge of allergic subjects with ryegrass antigen

The concentrations of the neuropeptides substance P, somatostatin, and calcitonin gene-related peptide in human nasal secretions were quantified by radioimmunoassays, concurrently with that of histamine, in the course of nasal challenge of allergic and control subjects with ryegrass antigen to examine contributions of neuromediation of the tissue response. Each of the neuropeptides and histamine were detected in nasal lavage fluid prior to challenge. In allergic patients, but not normal controls, antigen evoked significant increases of 3-fold in histamine at 15-60 min, 1.5- to 4-fold in calcitonin gene-related peptide at 15 min-24 hr, and more than 2-fold in somatostatin at 6 hr, without altering the concentration of substance P in nasal lavage fluid. The identity of the neuropeptides was confirmed chromatographically. Thus calcitonin gene-related peptide may mediate nasal congestion directly and somatostatin may be one of the factors regulating the late involvement of basophils and mast cells in allergic rhinitis.

Neuropeptide regulation of immediate and delayed hypersensitivity

Peptide mediators of sensory nerves that are released in tissues by noxious stimuli or inflammatory reactions rapidly elicit local and systemic responses similar to those of immediate hypersensitivity. These sensory neuropeptides affect functions of smooth muscles, blood vessels, leukocytes, and epithelial glands both directly and indirectly, through the actions of mediators released from mast cells stimulated by the peptides. Stereospecific receptors transduce the effects of neuropeptides of the peripheral nervous system (PNS) and central nervous system (CNS) on diverse functions of human, murine and guinea pig mononuclear and polymorphonuclear leukocytes, mast cells, and basophils in vitro and in vivo. Stimulatory and inhibitory effects of neuropeptides on leukocytes are attained in vitro at concentrations which are similar to those in the circulation and in tissues. The dissociation constant (KD) for the binding of a neuropeptide to its leukocyte receptor is within the range of concentrations that evoke cellular responses critical to immunity and hypersensitivity. Neuropeptides exhibit both cellular and stimulus specificities, as exemplified by the greater potency of substance P in activating mucosal than connective tissue mast cells and the capacity of somatostatin to inhibit the release of mediators from basophils challenged by IgE-dependent mechanisms, but not by basic peptides or ionophores. The selective release of distinct neuropeptides from different subsets of sensory nerve endings, the specificity of neuropeptide recognition by mast cells, basophils, lymphocytes, and other target cells, and the diversity of relevant activities of the neuropeptides suggest that the nervous system may initiate and modulate immediate and delayed hypersensitivity by unique mechanisms.