The cysteinyl-leukotriene D4 induces cytosolic Ca2+ elevation and contraction of the human detrusor muscle.
OBJECTIVE
The role of intracellular Ca2+ in the activation of human detrusor smooth muscle cells (SMCs) is pivotal. Recently we showed that the mast cell derived pro-inflammatory mediator leukotriene D(4) (LTD(4)) induces increase in intracellular free Ca2+ ([Ca2+](i)) in human detrusor myocytes. In the current study we examined the mechanisms underlying LTD(4) induced increase in [Ca2+](i) and tested whether LTD(4) induces muscle contraction by measuring force development in human detrusor tissue.


METHODS
Cultures of human detrusor SMCs were obtained from patients with benign bladder diseases undergoing cystoscopy. [Ca2+](i) was measured in fura-2 loaded SMCs using micro-spectrofluorometry and dynamic video imaging. Contractile force was monitored with an especially built mini-myograph.


RESULTS
Spontaneous oscillations in [Ca2+](i) and force were observed. In the absence of calcium these oscillations were absent. LTD(4) caused a concentration dependent increase in [Ca2+](i) and isometric force. Calcium was released exclusively from intracellular stores. Increases in [Ca2+](i) and force were inhibited in dose dependent fashion by the LTD(4) receptor antagonists montelukast and zafirlukast. Likewise, LTC(4) and LTE(4) induced an increase in [Ca2+](i) and contractile force in the rank order LTD(4) >LTC(4) >LTE(4). Inhibition of Ca2+ induced Ca2+ release (CICR) with thapsigargin and ryanodine suggested the presence of a functional CICR in SMCs.


CONCLUSIONS
To our knowledge this study demonstrates for the first time that the cysteinyl-leukotriene LTD(4) induces contraction in human detrusor SMCs. LTD(4) induced force and increased [Ca2+](i) were entirely dependent on Ca2+ release from intracellular stores. The action of LTD(4) on force development and increased [Ca2+](i) appeared to be specific, mediated by the binding and activation of specific LTD(4) receptors on SMCs. Also, to our knowledge this report is the first to show that human detrusor SMCs are sensitive to ryanodine, consistent with the hypothesis that a CICR is present and functional in these cells. The presence and role of endogenous cysteinyl leukotrienes for normal contractile functioning of the human detrusor during inflammation remains to be elucidated.
Bouchelouche
Kirsten
K
Smooth Muscle Laboratory and Department of Urology, Herlev Hospital, University of Copenhagen, Denmark.
Andersen
Lisa
L
Nordling
Jørgen
J
Horn
Thomas
T
Bouchelouche
Pierre
P
D000085:Acetates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003521:Cyclopropanes; D003545:Cysteine / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles; D020024:Leukotriene Antagonists / Q000494:pharmacology; D017998:Leukotriene D4 / Q000494:pharmacology*; D015289:Leukotrienes / Q000494:pharmacology*; D008565:Membrane Proteins; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D048448:Phenylcarbamates; D011804:Quinolines / Q000494:pharmacology; D018077:Receptors, Leukotriene / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013440:Sulfides; D013449:Sulfonamides; D014105:Tosyl Compounds / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D000085:Acetates; D003521:Cyclopropanes; D007211:Indoles; D020024:Leukotriene Antagonists; D015289:Leukotrienes; D008565:Membrane Proteins; D048448:Phenylcarbamates; D011804:Quinolines; D018077:Receptors, Leukotriene; D013440:Sulfides; D013449:Sulfonamides; D014105:Tosyl Compounds; C112381:cysteinyl-leukotriene; D017998:Leukotriene D4; C412375:cysteinyl leukotriene receptor 2; D003545:Cysteine; C083169:leukotriene D4 receptor; C093875:montelukast; D002118:Calcium; C062735:zafirlukast