CaCa2+2+ signallingsignalling in in healthhealth and and diseasedisease

Martin Hohenegger

Center for Physiology and Pharmacology

Institute of Pharmacology PhD-program

Pharmakologisches Institut der Medizinischen Universität Wien

CaCa2+2+freefree 1010--77 MM

CaCa2+2+free

10-3 M

CaCa2+2+free 10-3 M

InsP3cADPrNAADPCa2+

Depol.

Receptors

Ion channels

CaCa2+2+ distributiondistribution in and in and aroundaround cellscells

EncodingEncoding a Caa Ca2+2+ signalsignal

Amplitude decoded

Fequence decoded

EncodingEncoding a Caa Ca2+2+ signalsignal

SequentialSequential calciumcalciumamplificationamplification signalsignal

Blip/QuarkBlip/Quark: single channel

Puff/SparkPuff/Spark: single Channel unit

WaveWave: CICR

Global Global wavewave: concertedinteraction of cells

Skeletal muscle fibers and connective

tissues

ExcitationExcitation--ContractionContraction (EC) (EC) CouplingCoupling

(Anetseder and Roewer, Maligne Hyperthermie; Anästhesiologie, Springer Verlag, HD)

ExcitationExcitation NervNerv

Action potentialAction potential MuscleMuscle

depolarisationdepolarisation

CaCa2+2+ transienttransientRyRRyR

Tension Tension ActinActin

DevelopmentDevelopment MyosinMyosin

Voltage sensitive Ca2+ channels (Cav 1.1)Heteromultimers:

1 ion pore, gating function and drug binding site

2- , 2 highly glycosylated attached to -subunit via disulfide bonds; the domain modulates the kinetic properties

: localized intracellularly and is involved in the membrane trafficking of 1 subunits

: glycoprotein, having four transmembrane segments

Pharmakologisches Institut der Medizinischen Universität Wien

Adopted from : Melzer and Dietze, Acta Physiol. Scand. 171:367(2001)

SS

DHP - Receptor ( 15 )

TT - Membrane

I II III IV

Ryanodine receptor(RyR1)

N C

SR - Membrane

Ca2+

CaM

FKBP

2

1

ExcitationExcitation--ContractionContraction CouplingCouplingof Skeletal Muscleof Skeletal Muscle

Pharmakologisches Institut der Medizinischen Universität Wien

SS

DHP - Receptor ( 15 )

TT - Membrane

I II III IV

Ryanodine receptor(RyR1)

N C

SR - Membrane

Ca2+

FKBP

2

1

CaM

ExcitationExcitation--ContractionContraction CouplingCouplingof Skeletal Muscleof Skeletal Muscle

Adopted from : Melzer and Dietze, Acta Physiol. Scand. 171:367(2001)

Pharmakologisches Institut der Medizinischen Universität Wien

SS

DHP - Receptor ( 15 )

TT - Membrane

I II III IV

Ca2+

Ryanodine receptor(RyR1)

N C

SR - Membrane

Ca2+

FKBP

2

1

CaM

ExcitationExcitation--ContractionContraction CouplingCouplingof Skeletal Muscleof Skeletal Muscle

Adopted from : Melzer and Dietze, Acta Physiol. Scand. 171:367(2001)

Pharmakologisches Institut der Medizinischen Universität Wien

CaCa2+2+ Release Release channelchannel: : Ryanodine Ryanodine ReceptorReceptor

• Three isoforms; related to InsP3 receptor• RyR1(skeletal muscle) • RyR2 (cardiac) • RyR3 (brain, ubiquitous)

Pharmakologisches Institut der Medizinischen Universität Wien

Pharmakologisches Institut der Medizinischen Universität Wien, Hohenegger

Ryanodine receptor Type 1: skeletal muscle isoform

Type 2: cardiac isoform (also in brain and others)

Type 3: ubiquitous, with exceptions

Ryanodine, alkaloid from Ryania speciosa

NH2 COOH

TM 1-4

D1D3 D2

PP** CaMCaM

FKBP

Homotetramer: 560 kDa per subunit, 5037 aa

Ryanodine receptor Type 1

RyanodineInstitute of Pharmacology, Medical University Vienna, Hohenegger

EmergingEmerging mutationsmutations in RyR2 in RyR2

Associated with arrhythmia (catecholaminergic polymorphogenic ventricular tachycardia, suden heart death)

and heart failurePharmakologisches Institut der Medizinischen Universität Wien

RyRRyR11 and RyRand RyR22 mutationsmutations

Yano M et al. (2006)

Eindeutig zugewiesene Erkrankungen bei Eindeutig zugewiesene Erkrankungen bei

genetischen Defekten im genetischen Defekten im RyanodinrezeptorgenRyanodinrezeptorgen

RyR1- Mutationen: maligne Hyperthermie central core disease

RyR2- Mutationen:ARVC: arrhythmogenic right ventricular dysplasiaCPVT: Catecholaminergic polymorphic ventriculartachycardia

Pharmakologisches Institut der Medizinischen Universität Wien

Malignant Hyperthermia (MH)

• lifethreatening

• acute pharmacogenetic disorder

• developping during or after a generalanaesthesia

Other related diseasesCentral Core disease

Special RyR1 mutations:King-Denborough-Syndrom

RYR1 gene Arg2452Trp

NADH staining reduced =

less mitochondria

Fleckig/spotted = „core-like“

Muscular Dystrophieshigher risk vor malignant hyperthermia

Freeman Sheldon SyndromeMHC3 mutations: embryonic SKM myosin heavy chain 3 expressed

EtiologyEtiology and and PathogenesisPathogenesis of MH of MH withwithRyR1 RyR1 mutationsmutations

• autosomal-dominant inherited disorder, Chr.19q13.1

• incidence of the genetic MH predisposition is 1:10000

• clinical incidence about 1:30000; not every patient(mutation) developes a MH crisis

• specific early changes are the raise of the endexpiratoryCO2 together with the metabolic acidosis

• hyperthermia is a late sign.

• Rhabdomyolysis is a sign of the severity of the MH

Pathophysiology•Volatile anaesthetics (Chloroform, Ether, Halothane, Enflurane, Isoflurane, Sevoflurane, Deflurane)

• and/or suxamethonium, succinylxholine = 2 x Ach

• cause a raise in the myoplasmatic calcium concentration

• contractions lead to muscle injury and

• metabolic acidosis (when CO2 further raises then also respiratory acidosis)

• hyperkalemia, raised creatinkinase and myoglobinuria, arecaused by a damaged cell membrane

RhabdomyolyseRhabdomyolyse--MyoglobinurieMyoglobinurie

Necrosis

Differential Differential diagnosisdiagnosis

Thyreotoxicosis

Pheochromocytoma

Porphyria,

Histamine liberation (allergic reactions)

Hypovolemia

Hypoxia and hyperventilation

Epilepsia

Malignant neuroleptic syndrome

CaseCase reportreport

• Masseter spasm = chewing musculature

• Generalised skeletal muscle fasciculations

• Metabolic acidosis, later resiratory acidosis

• Raise of the creatin kinase and temperature

• Arrhythmias and tachycardia

TherapyTherapy I I

Masseterspasm or abortive MH crisis (mild form)

•Stop triggering (volatile anesthetics) and adminster 100% O2

•Deepen anesthesia with opioids, benzodiazepines (centralrelaxent), barbiturates or propofol

•Adjust ventilation according to blood gas analysis and endexpiratory CO2

•Check immediately, after 30 min, 4h, 12h, 24h blood gases, electrolytes, creatin kinase, myoglobin and lactat (arterialcatheter)

•Stop surgery, if fulminant MH crisis otherwise continue

•Give Dantrolene 2.5 mg/kg intravenous as bolus

TherapyTherapy IIIIFulminant MH crisis (severe form)

•Stop triggering, remove vaporizer and hyperventilation with100% O2

•Deepen anesthesia with opioids and sedatives, muscle relaxationwith a non depolarizing relaxant

•Check lab (see above), prepare dantrolene perfusion

•Dantrolene 2.5 mg/kg i.v. bolus, repeat bolus untilhypermetabolism stops (endexpiratory CO2), give dantrolen 10 mg/kg over 24 h continuously

•Sodium bicarbonate according to blood gas analysis or blind (1-2 mval/kg)

TherapyTherapy IIIIII

•Antiarrhythmic therapy with betablocker (esmolol 0.25 mg/kg i.v.) or lidocaine (1 mg/kg i.v.)

•Stop surgery as soon as possible

•Cooling: extremity or ice water through a nasogastric tube

•Postopersative Intensive care unit: monitoring: arterialcatheter, central venous catheter, swan-ganz-catheter, urinarycatheter; Force diuresis

•Check renal function, possible renal failure (myoglobin), coagulation, temperature, electrolytes and creatinkinase

ConsequencesConsequences

• Inform patient and relatives

• Test patient and relatives for MH susceptibility in a MH diagnostic center (in vitro contracture test, IVCT)

• If positive: MH susceptibility ID card

ConsequencesConsequences• Inform patient and relatives

• test patient and relatives for MH susceptibility in a MH diagnostic center (in vitro contracture test, IVCT)

• if positive: MH susceptibility ID card

In vitro In vitro contractioncontraction testtest

In vitro In vitro contractioncontraction testtest

MH

control

In vitro In vitro contractioncontraction testtestMH

control

TypicalTypical MH MH familyfamily

MH Abzeichen für Patientenmit positivem IVCT

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