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Neutrophil degranulation: therapeutic targets in [NTP]O mediated neutrophil degranulation
Medical Hypotheses (2004) 63, 325–327
http://intl.elsevierhealth.com/journals/mehy
Neutrophil degranulation: therapeutic targets in [NTP]O mediated neutrophil degranulation Subburaj Kannan* Department of Physiology, School of Medicine, Temple University, Philadelphia, PA 19140, USA Received 16 January 2002; accepted 8 May 2002
Summary Extracellular nucleotide-induced stimulation and activation of peripheral blood neutrophil and subsequent degranulation plays a critical role in immediate type hypersensitivity reaction and other inflammatory diseases. The extracellular nucleotides stimulate a P2Y receptor(s) on human PMN with the pharmacological profile similar to that of the P2Y2 receptor. Based on a recent proposal on the molecular mechanism of [NTP]O -induced neutrophil degranulation, a scheme identifying the therapeutic targets, is suggested with potential avenues for attenuating PMN degranulation. c 2004 Elsevier Ltd. All rights reserved.
Based on the proposal delineating the extracellular nucleotides induced neutrophil degranulation [1], the following aspect(s) of the scheme would be conceivable as rational therapeutic targets in attenuating the effect of [NTP]O in PMN degranulation. Stage . Receptor specific neutralizing antibodies: generating and characterizing an P2Y2 receptor exofacial domain specific antibody (monoclonal or polyclonal) could be used to block the [NTP]O binding to the active ligand binding site of the receptor at Stage . [2,3]. Receptor specific antagonists and/or inhibitors directed against P2Y2 Receptor could be of strategic importance. Upon neutralizing the [NTP]O binding to its receptor, essentially the PMN degranulation will be attenuated. Through, high through put screening of large libraries of small molecules, identification of the *
Present address: Department of Microbiology and Immunology, University of Texas Medical Branch, P.O. Box 25056, Galveston, TX 77555, USA. Tel./fax: +1-409-750-9060. E-mail addresses: [email protected], [email protected].
appropriate candidate compound could be used to inhibit competitively the binding of the ligand(s) to its active ligand binding site of the receptor(s). Compound(s) with competitive inhibition would be more appropriate, because of the fact it will bind to the active site of the receptor. If the active ligand-binding site is embedded in the transmembrane region, this class of the inhibitor will cause non-specific effect on receptor homologues in the vicinity. This concept is valid and applicable for the nucleotide receptor P2Y2 [4]. Antisense approach involving the antisense oligo’s directed against P2Y2R specific sequence that could potentially decrease the level of formation of the P2Y2R [5]. Stage . Inhibition of the arachidonic acid formation from the membrane bound phospholipids, could be achieved by utilizing inhibitors specific for the phospholipase isoforms is of significance interms of blocking the arachidonic acid formation. Thus, reducing the availability of the substrate for the 5-lipoxygenase, which mediates the leukotriene synthesis. Stage . Blocking the formation and transport of LTB4 for transcellular metabolism is
0306-9877/$ - see front matter c 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mehy.2002.05.001
326
Kannan
critical in terms of limiting its significant stimulatory effect on the transcellular signaling effect (see Fig. 1). Stage . Leukotriene B4 receptor (LTB4 R) specific antagonists like U75302 could potentially attenuate LTB4 binding to its receptor is of prime significance as LTB4 has been proposed to be essential inter mediate in the [NTP]O or fMLP or PAF stimulated neutrophil(s) resulting degranulation. Stage . Obviously subsequent to the LTB4 binding to its receptor a signaling cascade is expected to take place involving possibly or potentially the Stress Activated Protein kinases or (e.g., p38MAPkinase; p44MAPkinases; c-JUN N-terminal kinases) in granule mobilization and fusion to membrane to result the degranulation processes to complete. Inhibition of the kinases which are known to be the intermediate in the down stream signaling cascade that will limit the exacerbation of LTB4 formed in response to the [NTP]O -induced PMN stimulation [6,7]. Stage . Even though it is known that granule mobilization is stimulated by cytochlasin B in vitro, implicating cytoskeletal network in this processes, the molecular mechanism is not known at present. Agents that inhibit
the granule mobilization towards fusing to the membrane would play a significant role in the last but the critical stage of the degranulation processes. Stage . It is not known whether LTB4 could directly induce or enhance the granule mobilization and fusion to the membrane in order to facilitate the degranulation processes. Blocking this step would possibly decrease the granule mobilization and fusion to membrane. Thus, reducing the effect of granule content release in to the inflamed vasculature [8]. Stage . At present it is unclear as to whether up regulation of phospholipases alone can have direct role in up regulating the fusion of granule(s) with the membrane there by exacerbating the degranulation processes [8]. Stage . While it is known that [NTP]O alone cannot act as a sole agonist in inducing the PMN degranulation, co-stimulatory/priming agent(s) such as fMLP or PAF or TNF are required for the PMN degranulation to occur. As identified can the priming or co-stimulatory molecules alone can act directly to induce the PMN degranulation. The inter junction of the two divergent pathways, one mediated by [NTP]O and other mediated by co-
Figure 1
Neutrophil degranulation stimulatory signals mediated by (fMLP; PAF) is not known at present, but likely to be the LTB4 . Therefore, blocking the merger of two distinct pathways will essentially limit or attenuate the [NTP]O orco stimulatory/priming agent(s) such as fMLP or PAF or TNF induced degranulation.
References [1] Kannan S. Neutrophil degranulation: coactivation of chemokine receptor(s) is required for extracellular nucleotideinduced neutrophil degranulation. Med Hypotheses 2001;57:306–9. [2] Domingo E, Verdaguer N, Ochoa WF, Ruiz-Jarabo CM, Sevilla N, Baranowski E, Mateu MG, Fita I. Biochemical and structural studies with neutralizing antibodies raised against foot-and-mouth disease virus. Virus Res 1999;62: 169–75.
327 [3] Horowski R, Sturzebecher CS, Kapp JF. Neutralizing antibodies (NABS) and interferon beta-1b therapy of multiple sclerosis. Funct Neurol 2001;16:117–28. [4] Fox DA. Cytokine blockade as a new strategy to treat rheumatoid arthritis: inhibition of tumor necrosis factor. Arch Intern Med 2000;160:437–44. [5] Baker BF, Condon TP, Koller E, McKay RA, Siwkowski AM, Vickers TA, Monia BP. Discovery and analysis of antisense oligonucleotide activity in cell culture. Methods 2001;23:191–8. [6] Fukami Y, Tokmakov AA, Konaka K, Sato K. Peptide inhibitors of the mitogen-activated protein kinase pathway: a structure-mimetic peptide corresponding to the conserved interDFG-APE region in the kinase domain. Pharmacol Ther 1999;82:399–407. [7] Howard OM, Oppenheim JJ, Wang JM. Chemokines as molecular targets for therapeutic intervention. J Clin Immunol 1999;19:280–92. [8] Yokomizo T, Izumi T, Shimizu T. Leukotriene B4: metabolism and signal transduction. Arch Biochem Biophys 2001;385:231–41.
http://intl.elsevierhealth.com/journals/mehy
Neutrophil degranulation: therapeutic targets in [NTP]O mediated neutrophil degranulation Subburaj Kannan* Department of Physiology, School of Medicine, Temple University, Philadelphia, PA 19140, USA Received 16 January 2002; accepted 8 May 2002
Summary Extracellular nucleotide-induced stimulation and activation of peripheral blood neutrophil and subsequent degranulation plays a critical role in immediate type hypersensitivity reaction and other inflammatory diseases. The extracellular nucleotides stimulate a P2Y receptor(s) on human PMN with the pharmacological profile similar to that of the P2Y2 receptor. Based on a recent proposal on the molecular mechanism of [NTP]O -induced neutrophil degranulation, a scheme identifying the therapeutic targets, is suggested with potential avenues for attenuating PMN degranulation. c 2004 Elsevier Ltd. All rights reserved.
Based on the proposal delineating the extracellular nucleotides induced neutrophil degranulation [1], the following aspect(s) of the scheme would be conceivable as rational therapeutic targets in attenuating the effect of [NTP]O in PMN degranulation. Stage . Receptor specific neutralizing antibodies: generating and characterizing an P2Y2 receptor exofacial domain specific antibody (monoclonal or polyclonal) could be used to block the [NTP]O binding to the active ligand binding site of the receptor at Stage . [2,3]. Receptor specific antagonists and/or inhibitors directed against P2Y2 Receptor could be of strategic importance. Upon neutralizing the [NTP]O binding to its receptor, essentially the PMN degranulation will be attenuated. Through, high through put screening of large libraries of small molecules, identification of the *
Present address: Department of Microbiology and Immunology, University of Texas Medical Branch, P.O. Box 25056, Galveston, TX 77555, USA. Tel./fax: +1-409-750-9060. E-mail addresses: [email protected], [email protected].
appropriate candidate compound could be used to inhibit competitively the binding of the ligand(s) to its active ligand binding site of the receptor(s). Compound(s) with competitive inhibition would be more appropriate, because of the fact it will bind to the active site of the receptor. If the active ligand-binding site is embedded in the transmembrane region, this class of the inhibitor will cause non-specific effect on receptor homologues in the vicinity. This concept is valid and applicable for the nucleotide receptor P2Y2 [4]. Antisense approach involving the antisense oligo’s directed against P2Y2R specific sequence that could potentially decrease the level of formation of the P2Y2R [5]. Stage . Inhibition of the arachidonic acid formation from the membrane bound phospholipids, could be achieved by utilizing inhibitors specific for the phospholipase isoforms is of significance interms of blocking the arachidonic acid formation. Thus, reducing the availability of the substrate for the 5-lipoxygenase, which mediates the leukotriene synthesis. Stage . Blocking the formation and transport of LTB4 for transcellular metabolism is
0306-9877/$ - see front matter c 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mehy.2002.05.001
326
Kannan
critical in terms of limiting its significant stimulatory effect on the transcellular signaling effect (see Fig. 1). Stage . Leukotriene B4 receptor (LTB4 R) specific antagonists like U75302 could potentially attenuate LTB4 binding to its receptor is of prime significance as LTB4 has been proposed to be essential inter mediate in the [NTP]O or fMLP or PAF stimulated neutrophil(s) resulting degranulation. Stage . Obviously subsequent to the LTB4 binding to its receptor a signaling cascade is expected to take place involving possibly or potentially the Stress Activated Protein kinases or (e.g., p38MAPkinase; p44MAPkinases; c-JUN N-terminal kinases) in granule mobilization and fusion to membrane to result the degranulation processes to complete. Inhibition of the kinases which are known to be the intermediate in the down stream signaling cascade that will limit the exacerbation of LTB4 formed in response to the [NTP]O -induced PMN stimulation [6,7]. Stage . Even though it is known that granule mobilization is stimulated by cytochlasin B in vitro, implicating cytoskeletal network in this processes, the molecular mechanism is not known at present. Agents that inhibit
the granule mobilization towards fusing to the membrane would play a significant role in the last but the critical stage of the degranulation processes. Stage . It is not known whether LTB4 could directly induce or enhance the granule mobilization and fusion to the membrane in order to facilitate the degranulation processes. Blocking this step would possibly decrease the granule mobilization and fusion to membrane. Thus, reducing the effect of granule content release in to the inflamed vasculature [8]. Stage . At present it is unclear as to whether up regulation of phospholipases alone can have direct role in up regulating the fusion of granule(s) with the membrane there by exacerbating the degranulation processes [8]. Stage . While it is known that [NTP]O alone cannot act as a sole agonist in inducing the PMN degranulation, co-stimulatory/priming agent(s) such as fMLP or PAF or TNF are required for the PMN degranulation to occur. As identified can the priming or co-stimulatory molecules alone can act directly to induce the PMN degranulation. The inter junction of the two divergent pathways, one mediated by [NTP]O and other mediated by co-
Figure 1
Neutrophil degranulation stimulatory signals mediated by (fMLP; PAF) is not known at present, but likely to be the LTB4 . Therefore, blocking the merger of two distinct pathways will essentially limit or attenuate the [NTP]O orco stimulatory/priming agent(s) such as fMLP or PAF or TNF induced degranulation.
References [1] Kannan S. Neutrophil degranulation: coactivation of chemokine receptor(s) is required for extracellular nucleotideinduced neutrophil degranulation. Med Hypotheses 2001;57:306–9. [2] Domingo E, Verdaguer N, Ochoa WF, Ruiz-Jarabo CM, Sevilla N, Baranowski E, Mateu MG, Fita I. Biochemical and structural studies with neutralizing antibodies raised against foot-and-mouth disease virus. Virus Res 1999;62: 169–75.
327 [3] Horowski R, Sturzebecher CS, Kapp JF. Neutralizing antibodies (NABS) and interferon beta-1b therapy of multiple sclerosis. Funct Neurol 2001;16:117–28. [4] Fox DA. Cytokine blockade as a new strategy to treat rheumatoid arthritis: inhibition of tumor necrosis factor. Arch Intern Med 2000;160:437–44. [5] Baker BF, Condon TP, Koller E, McKay RA, Siwkowski AM, Vickers TA, Monia BP. Discovery and analysis of antisense oligonucleotide activity in cell culture. Methods 2001;23:191–8. [6] Fukami Y, Tokmakov AA, Konaka K, Sato K. Peptide inhibitors of the mitogen-activated protein kinase pathway: a structure-mimetic peptide corresponding to the conserved interDFG-APE region in the kinase domain. Pharmacol Ther 1999;82:399–407. [7] Howard OM, Oppenheim JJ, Wang JM. Chemokines as molecular targets for therapeutic intervention. J Clin Immunol 1999;19:280–92. [8] Yokomizo T, Izumi T, Shimizu T. Leukotriene B4: metabolism and signal transduction. Arch Biochem Biophys 2001;385:231–41.