Transcript Document

Cellular communications present
in cardiovascular system
In this system are involved many biological
substances of different therapeutic importance
and relevance with different signal transductions
Blood Pressure Regulation
Sympathetic nervous control
Blood Pressure Regulation
Involvement of RAS system
Drugs affecting the cardiovascular apparatus
Most prescribed classes of antihypertensive drugs (US)
Beta blockers and ACE inhibitors account for 58% of all antihypertensives prescribed in the US.
Antihypertensive drugs
ACE inhibitors, indications include heart failure, left ventricular dysfunction and diabetic
nephropathy; contra-indications include renovascular disease and pregnancy;
Angiotensin-II receptor antagonists are alternatives for those who can not tolerate ACE
inhibitors because of persistent dry cough, but they have the same contra-indications as
ACE inhibitors.
Beta-blockers, indications include myocardial infarction, angina; compelling contra-indications
include asthma, heart block;
Calcium-channel blockers: are valuable in isolated systolic hypertension in the elderly when a
low-dose thiazide is contra-indicated or not tolerated.
Alpha-blockers, a possible indication is prostatism; a contra-indication is urinary incontinence;
Diuretics, particularly indicated for hypertension in the elderly; a contra-indication is gout;
Drugs affecting the renin-angiotensin system (RAS)
1.
2.
3.
Renin inhibitors,
Angiotensin-converting enzyme inhibitors
Angiotensin-II receptor antagonists
Therapeutic application for:
HYPERTENSION
ACE inhibitors should be considered for hypertension when thiazides and beta-blockers are
contra-indicated, not tolerated, or fail to control blood pressure.
HEART FAILURE
ACE inhibitors have a valuable role in all grades of heart failure, usually combined with a
diuretic.
MYOCARDIAL INFARCTION
ACE inhibitors are used in the immediate and long-term management of patients who have
had a myocardial infarction.
Angiotensin-II receptor antagonists, although not licensed for heart failure, may be useful
alternatives for patients who, because of symptoms such as cough, cannot tolerate ACE
inhibitors.
Renin-Angiotensin System
vasopressin
La secrezione di renina
renina
La
è un enzima proteolitico che viene secreto nel circolo
ematico delle cellule dell’apparato iuxtaglomerulare, un agglomerato
di cellule di origine muscolare, che rivestono le arteriole afferenti
determinandone la pressione interna.
Gli stimoli per la liberazione di renina sono:
a)di origine neuronale, neuroni simpatici b-1,
b)quantità di liquido che passa nelle arteriole (pressione di perfusione
renale)
c)concentrazione di ioni sodio nei fluidi presenti nel tubulo distale al
quale è esposta la macula densa. (Le cellule della macula densa sono in
grado di sintetizzare prostanoidi che danno un segnale positivo di
secrezione alla juxtaglomerulare e negativo con la secrezione di
adenosina).
Comunicazione paracrina per la sintesi di renina
Corpuscolo renale
L'apparato juxtaglomerulare è indicato dalla lettera D e comprende:
5b. Mesangio – cellule extraglomerulari
6. Cellule granulari (cellule juxtaglomerulari)
7. Macula densa
RENIN-ANGIOTENSIN CASCADE
Angiotensinogen is the precursor molecule, and it is produced mainly in the liver, (although other sites
have been thought to contribute to local effects of the molecule).
In humans, the peptide sequence for angiotensinogen (485 amino acids long) which contains (immediatly
after the signal peptide) the 10 aa:
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Xaa-XbbRenin acts to cleave the peptide bond between the leucine (Leu) and the valine (Val) residues.
The ten amino acid peptide (bold) angiotensin I is created.
Angiotensinogen
Angiotensinogen is an  -2-globulin, a group of globular proteins in
plasma, that is produced constitutively and released into the circulation
mainly by the liver.
It is a member of the SERPIN family, a group of proteins with similar
structures that were first identified as a “set of proteins” able to inhibit
proteases, (the acronym serpin was originally coined because many
serpins inhibit chymotrypsin-like enzymes, serine protease inhibitors),
although it is not known to inhibit other enzymes, unlike most serpins.
Plasma angiotensinogen levels are increased by plasma corticosteroid,
estrogen, thyroid hormone, and angiotensin II levels.
Angiotensinogen is also known as renin substrate.
Human angiotensinogen is 452 amino acids long, but other species have
angiotensinogen of varying sizes.
The first 12 amino acids are the most important for activity.
ACE processing
The decapeptide angiotensin I (AI) is cleaved into the octapeptide angiotensin II (AII) by
angiotensin-converting enzyme (ACE).
Angiotensin-converting enzyme (ACE) has a critical role in cardiovascular function by cleaving
the carboxy terminal His-Leu dipeptide from angiotensin I to produce a potent vasopressor
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu
octapeptide, angiotensin II.
+ H-L
Localizzazione dell’ ACE
L’ACE è un enzima di membrana posto sulla superficie delle cellule endoteliali, ed
è particolarmente abbondante nei polmoni dove è presente una superficie di
endotelio vascolare molto grande.
La proteina enzimatica è presente anche in altri tessuti vascolari del cuore, del
SNC, nel muscolo striato e la sua localizzazione non sembra limitata al solo
endotelio.
The endothelium is the thin layer of cells that lines the interior surface of blood vessels,
forming an interface between circulating blood in the lumen and the rest of the vessel wall.
ACE cleaves also Bradykinin peptides
Inhibitors of ACE are a first line of therapy for hypertension, heart failure,
myocardial infarction and diabetic nephropathy.
Notably, these inhibitors were developed without knowledge of the structure of human
ACE, but were instead designed on the basis of an assumed mechanistic homology with
Carboxypeptidase A.
The peptidase reaction
R
H
N
O
A peptide substrate
R'
Enzyme + H2O
R
OH
O
H2N
R'
RENIN is an Aspartyl Proteases,
a sub-subclass of ENDOPEPTIDASES that depend on an
ASPARTIC ACID residue for their activity. EC 3.4.23.
Mammalian Renin
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Xaa-Xbb-
Design of renin inhibitors
pseudopeptide
amino component
The time neded to develop renin inhibitor to use in therapy
Tekturna: the first renin inhibitor
Tekturna (Aliskiren) was approved by the FDA in March 2007 and it is the first renin inhibitor and the
first member of a new class of antihypertensive drugs in a decade.
The drug inhibits the activity of renin, leading to a decrease in angiotensin I and a subsequent
reduction in angiotensin II.
Specific inhibitors of renin reduce Ang II generation, but unlike ACE-inhibitors they do not cumulate
other peptides like Substance P or Bradykinin and consequently untoward drug effects like:
cough and angioedema are not to be expected.
Several specific renin inhibitors were synthesized as of the 1970s, but low efficacy or the lack of oral
availability or high cost of synthesis always prevented renin inhibitors from becoming successful drugs.
OH
H2N
*
H
N
*
*
*
O
NH2
O
O
O
O
COOH
HOOC
2(S),4(S),5(S),7(S)-N-(2-carbamoyl-2-methylpropyl)-5-amino-4-hydroxy-2,7-diisopropyl-8-[4-methoxy-3-(3-methoxypropoxy-)phenyl]octanamid hemifumarate
Design of ACE inhibitors
Knowledge of the
similar enzyme
Carboxypeptidase A
A mechanism of Carboxypeptidase A
Carboxypeptidase A is a digestive enzyme that hydrolyzes the carboxyl-terminal peptide
bond in polypeptide chains.
The enzyme serves as a good illustration of protein secondary structure. The single polypeptide chain
of 307 amino acids contains regions of alpha helix (385) and beta pleated sheet (17%).
Hydrolysis occurs most readily if the carboxyl-terminal residue has an aromatic
or a bulky aliphatic side chain
Catalitic mechanism of CPA
Binding of a typical substrate such as glycyl-tyrosine results in a structural rearrangement of the active
site (induced fit). Residues which are thought to interact with the substrate include Glutamate 270,
Arginine 145, Arginine 127, and Tyrosine 248.
A zinc atom is coordinated in a tetrahedral array with the amino acids Histidine 69, Histidine 196,
and Glutamate 72, and either a water or substate molecule. The zinc atom is a prosthetic group that is
essential for enzymatic activity and is largely responsible for the electronic strain created at the active
site. In the illustration below, zinc polarizes the carbonyl group of the peptide bond in glycyl-tyrosine,
making it more susceptible to attack by Glutamate 270.
Subtrate and inhibitor of CPA
Requirements of CPA and ACE for the development of enzyme inhibitors
OH
O
EDITPEP
OH
N
H
O
O
CPA inhibitor
CPA substrate
HN
HN
N
N
O
EDITPEP
OH
R
N
H
H
N
O
H
N
R
OH
O
OH
O
O
ACE substrate
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-OH
ACE inhibitor ?
Interaction of ACE with a substrate
Angiotensin I
Phe
His
Leu-OH
Glu H2O
Angiotensin I
is a substrate
of ACE
Arg
His
His
His
Design of ACE inhibitors considering the knowledge of CPA inhibitors
O
H
N
O
R
N
H
R'
O
HS
R'
OH
O
R
N
H
OH
O
Teprotide, is a Bradykinin-Potentiating Peptide
Pyr-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro-OH
In the 1960 it was observed that the venom of the Brazilian pit viper Bothrops jararaca, contains
peptides capable of intensifying responses to bradykinin.
The venomous peptides tourned out to be inhibitors of kininase II, a bradikynin-inactivating
enzyme, which subsequently was shown to be identical with ACE.
Based on the sequence of one of the key venomous peptides, the peptide teprotide was synthesized
and shown also to be an inhibitor of ACE.
The presence of Pro residues and an N-terminal Pyroglutammic acid, made the teprotide
relatively resistant to proteolytic decomposition in vivo, but it was not sufficiently stable for oral
administration.
Teprotide became the primary lead struucture in a drug design project aiming at the development
of the low-molecular weight analogues showing potent ACE inhibition activity and desirable
pharmacokinetic properties.
Two structural features were considerd essential for activity, namely the presence of a C-terminal
Pro residue and a functional group capable of co-ordinating effectively with the zinc atom in the enzyme.
As a result of the sistematic reduction of the moleculat weight of teprotide following this strategy and
by using bovin carboxypeptidase A as the assay enzyme, N-succinyl-Pro was synthesized and shown to
be a mederately potent ACE inhibitor.
HN N
O
HO
O
COOH
N
H
N
R
O
O
OH
Ace Inhibitors in therapy
captopril - Capoten by Bristol-Myers Squibb
enalapril - Vasotec by Merck benazepril - Lotensin by Novartis
lisinopril - Prinivil by Merck or Zestril by Astra-Zeneca
quinapril - Accupril by Pfizer
ramipril - Altace by Hoechst Marion Roussel, King Pharmaceuticals
moexipril/spirapril - Univasc by Schwarz Pharma
trandolapril - Mavik by Knoll Pharmaceutical (BASF)
perindopril erbumine - Aceon by Rhone-Polenc Rorer
imidapril - Not approved for human use in the USA - approved in Japan
fosinopril - Monopril by Bristol-Myers Squibb
O
HS
COOH
N
Captopril
(S)-1-(3-Mercapto-2-methyl-1-oxopropyl)-L-proline
Chemical approach to captopril analogues HN
N
O
EDITPEP
N
H
O
HO
O
H
N
O
COOH
N
O
ACE substrate
OH
O
O
HO
O
HS
COOH
N
COOH
N
O
Captopril
modify distance
HO
O
H
N
COOH
N
R
New analogues
O
H
N
O
O
HO
R
N
H
R'
OH
O
O
H
N
Design of ENALAPRIL
COOH
H
N
N
R
Enalapril
H3 C-H 2C-OOC
O
COOH
N
(S)-1-[N2-[(1-Etossicarbonyl)-3-phenylpropyl-]-L-alanyl-]-L-proline
H
N
HOOC
O
COOH
N
(S)-1-[N-(1-Carboxy-3-phenylpropyl-)-L-alanyl-]-L-proline
Design of ENALAPRIL analogues with modifications
at the Alanine or Proline residue
H
N
HOOC
Lisinopril
O
COOH
N
H
N
H3 C-H 2C-OOC
H2N
(S)-1-[N2-[(1-Carboxy)-3-phenylpropyl-]-L-lysyl-]-L-proline
O
COOH
N
Quinapril
H
N
H
N
H3 C-H 2C-OOC
O
COOH
H3 C-H 2C-OOC
O
COOH
N
N
(S)-2-[2-[[1-(Ethoxycarbonyl)-3-phenylpropyl-]-amino-]-1-oxopropyl]-1,2,3,4-tetrahydroisoquinolin-3-carboxylic acid
COOH
COOH
H2N
COOH
HN
HN
COOH
HN
Pipecolic acid
Phe
Tic, a constrained analog of Phe
an analog of Pro
H
N
O
N
H3 C-H 2C-OOC
H
N
H3 C-H 2C-OOC
O
H
COOH
COOH
COOH
N
HN
H
COOH
HN
H
H
Ramipril
(S)-1-[2-[[1-(Ethoxycarbonyl)-3-phenylpropyl]-amino]-1-oxopropil]-octaidrociclopenta-[b]-pirrolo-2-carboxylic acid
H
N
Trandolapril
H3 C-H 2C-OOC
H
N
H3 C-H 2C-OOC
O
H
COOH
O
COOH
N
Enalapril
N
H
(S)-1-[2-[[1-(Ethoxycarbonyl)-3-phenylpropyl-]-amino-]-oxopropil]-octaidro-1H-indolo-2-carboxylic acid
H
N
O
N
H3 C-H 2C-OOC
H
N
H3 C-H 2C-OOC
O
COOH
COOH
Spirapril
N
S
S
COOH
HN
(8S)-7-(2S)-[2-[[(1S)-1(-etoxycarbonyl)-3-phenylpropyl]-amino]-1-oxopropyl]1,4-dithia-7-azaspiro[4,4]nonan-8-carboxylic acid
COOH
HN
S
S
H
N
H3 C-H 2C-OOC
H
N
H3 C-H 2C-OOC
O
O
COOH
N
COOH
N
COOH
HN
COOH
HN
N-alkyGly
Delapril
(S)-N1-(2,3-Dihydro-1H-inden-2-yl)-N1-[N2-(1-ethoxycarbonyl)-3-phenylpropyl-]L-alanil-]-glicine
Design of ENALAPRIL analogues with modifications
at the Ala and Pro residues
O
H
N
COOH
H
N
O
H3 C-H 2C-OOC
COOH
N
N
N
H3 C-H 2C-OOC
Cilazapril
[S-[1a, 9a ]-9-[1-(etossicarbonil)3-fenilpropil]-amino]-octaidro-10-oxo-6H-piridazino-[1,2a][1,2]-diazepin-1-carbossilico acido
COOH
H2N
COOH
H2N
COOH
COOH
Glu
COOH
HN
HN
Piperazic acid
HN
H
N
H3 C-H 2C-OOC
O
H
N
COOH
N
H3 C-H 2C-OOC
Quinapril
O
COOH
N
O
H
N
COOH
N
H3 C-H 2C-OOC
Delapril
H
N
O
COOH
N
N
H3 C-H 2C-OOC
Cilazapril
H
N
H3 C-H 2C-OOC
O
COOH
N
H2N
O
COOH
N
H2N
O
N
N
Benazepril
(3S)3-[[(1S) 1-(etossicarbonil)-3-fenilpropil]-amino]-2,3,4,5-tetraidro-2-oxo-1H-1-benzazepin-1-acetico acido
COOH
Design of ENALAPRIL analogues with modifications
in different points of the molecule
O
H
N
N
H3 C-H 2C-OOC
General structure of
these derivatives
O
R2
p
R3 O
O
X
COOH
N
R1
COOH
R
O
HS
COOH
N
X= CH2 , O, NH, o r a b sent
O
P
O
O
COOH
N
O
X is absent, R1 is H, R2 is an alkyl
group and R3 is an ether/ester function
O
Fosinopril
(4S) 4-Cyclohexyl-1-[[[2-methyl-1(1-oxopropoxy)-propoxy]-(4-phenybuthyl)-phosphinyl]-acetyl]-L-proline
Zofenopril calcium chemically known as (4S)-l-[(2S)-3-(benzoylthio)-2-methylpropionyl]-4- (phenylthio)-L-proline calcium salt
Zofenopril is a non-peptidic orally active sulphydryl ACE inhibitor with long
lasting action, which is approved for the treatment of hypertension.
It is a further modification of the CAPTOPRIL, the first ACE inhibitor
Angiotensin-II receptor antagonists
Candesartan, irbesartan, losartan, and valsartan
are specific angiotensin-II receptor antagonists with many properties similar to those of the
ACE inhibitors.
Eprosartan, olmesartan, and telmisartan have been introduced more recently.
However, unlike ACE inhibitors, they do not inhibit the breakdown of bradykinin and other
kinins, and thus do not appear to cause the persistent dry cough which commonly complicates
ACE inhibitor therapy.
This panel shows the Angiotensin II and AT1 receptor in cartoon mode, with some of the
loops connecting the helices omitted for clarity. This 3D-structure is a model based on the
rhodopsin receptor to guide folding of the AT1-receptor sequence.
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-OH
Angiotensin II receptor, type 1
Angiotensin II receptor, type 1 or AT1 receptor is an angiotensin receptor. It has vasopressor effects
and regulates aldosterone secretion. It is an important effector controlling blood pressure and
volume in the cardiovascular system.
Angiotensin II receptor antagonists are drugs indicated for hypertension, diabetic nephropathy and
congestive heart failure
The angiotensin receptor is activated by the vasoconstricting peptide angiotensin II.
The activated receptor in turn couples to Gq/11 and thus activates Phospholipase C and increases the
cytosolic Ca2+ concentrations, which in turn triggers cellular responses such as stimulation of protein
kinase C.
Activated receptor also inhibits adenylate cyclase and activates various tyrosine kinases.
Angiotensin II receptor, type 2
AT2 belongs to a family 1 of G protein-coupled receptors, it is an integral membrane protein that plays a
role in the central nervous system and cardiovascular functions that are mediated by the renin-angiotensin
system. This receptor mediates programmed cell death (apoptosis).
In adults, it is highly expressed in myometrium with lower levels in adrenal gland and fallopian tube.
Stimulation of AT2 by the selective agonist increases mucosal nitric oxide production
Amino acid residues of AII involved
in receptor interaction
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-OH
Binding of Angiotensin II to the AT1
receptor, looking down on the receptor
from the top, circles represent
transmembrane helicies .
Some transmembrane helicies have been
omitted for clarity.
The N-terminal region of angiotensin is
represented by R for simplicity.
The D(Asp 281) N(Asn 111) K(Lys 199)
H(His 256) binding sequence is shown in
RED, other amino acids that are
peripherally related in stabilizing the
molecule are shown in BLACK.
Drugs act by mimicking the structure of the natural neurotransmittesr and hormones.
There may be an almost direct structural correspondence between the drug and hormone
(e.g. saralasin/angiotensin) or the structures may be superficially quite different (e.g. losartan), but the
drugs shape and electrostatic charge distribution mimics the shape and charge of the natural compound.
Whether a drug is an agonist or antagonist depends on a number of structural issues.
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-OH, angiotensin II
agonist
H-Sar-Arg-Val-Tyr-Val-His-Pro-Ala-OH, SARALASIN
antagonist
Design of Losartan
H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-OH, angiotensin II
Cl
N
Cl
COOH
N
COOH
N
N
R
R
R = Cl, NO2, CH3, OH, OCH3
X
X = spacer, CH2, O, CO-NH, CH=CH, etc.
Design of Losartan
Losartan
Cl
N
Cl
OH
N
COOH
N
N
N N
N
N
H
R
R = CO OH or oth er groups
2-Butyl-4-chloro-1 {[2'-(1H-tetrazol-5-yl)-1,1’-biphenyl-4-yl]methyl}-1H-imidazol-5-methanol
Cl
N
OH
N
Design of LOSARTAN analogues
N N
N
N
H
N
O
N
COOH
N
O
O
N
O
N N
N
N
H
candesartan
O
O
O
N N
N
N
H
Candesartan cilexetil
2-etossi-1-[[2'-(1H-tetrazol-5-il)[1,1'-bifenil]-4-il]-metil]-1H-benzimidazolo-7-carbossilico acido
Cl
N
OH
N
N
N
irbesartan
O
N N
N
N
H
2-butil-3-[[2'-(1H-tetrazol-5-il)-1,1'-bifenil-4-il]-metil]-1,3-diazaspiro[4.4]non-1-en-4-one
N N
N
N
H
Cl
N
O
OH
N
N
COOH
N N
N
N
H
valsartan
N-(1-oxopentil)-N-[[2'-(1H-tetrazol-5-il)-1,1'-bifenil-4-il]-metil]-L-valina
N N
N
N
H
Fine presentazione
L'adenoipofisi secerne sei importanti ormoni:
il GH (Ormone della Crescita o Somatotropina), che regola la crescita ed il metabolismo intermedio;
la PRL (Prolattina), essenziale per la produzione del latte durante la gravidanza ed il puerperio;
l'LH (Ormone Luteinizzante) e l'FSH (Ormone Follicolo Stimolante), che controllano le funzioni gonadiche
nell'uomo e nella donna;
il TSH (Ormone Tiroido Stimolante o Tireotropina), che regola la funzione della tiroide;
l'ACTH (Ormone Adrenocorticotropo) che, regolando le funzioni della corteccia delle ghiandole surrenali,
influenza i livelli di cortisolo circolanti.
La neuroipofisi svolge la sua funzione agendo da "serbatoio" per due ormoni prodotti dai neuroni dell'ipotalamo:
la Vasopressina (AVP o Ormone Antidiuretico), che controlla l'equilibrio idrico dell'organismo agendo sul rene;
l'Ossitocina ha, invece, importanza nel regolare la lattazione ed i fenomeni del parto.omeni del parto.
Comparison of binding of angiotensin (left hand panel) and
the antagonist Losartan (Right hand panel) to the AT1
receptor
This is a molecular model of the unbound
carboxypeptidase A enzyme. The cpk, or
space-filled, representation of atoms is
used here to show the approximate
volume and shape of the active site.
Note the zinc ion (magenta) in the
pocket of the active site. Three amino
acids located near the active site
(Arg 145, Tyr 248, and Glu 270) are labeled.
This is a cpk representation of carboxypeptidase A
with a substrate (turquoise) bound in the active site.
The active site is in the induced conformation.
The same three amino acids (Arg 145, Tyr 248,
and Glu 270) are labeled to demonstrate the shape
change.
Tekturna: the new kid on the block
•
Novartis's Tekturna (aliskiren) was approved by the FDA in March 2007 and is the first renin inhibitor and
the first member of a new class of antihypertensive drugs in a decade. The drug inhibits the activity of renin,
leading to a decrease in angiotensin I and a subsequent reduction in angiotensin II. Late-stage trials with
Tekturna used as monotherapy (75–600 mg daily), showed a significant decline in blood pressure compared
with placebo.
•
Specific inhibitors of renin reduce Ang II generation, but unlike ACE-inhibitors they do not cumulate other peptides
like substance P or bradykinin and consequently untoward drug effects like cough and angioedema are not to be
expected.
•
Several specific renin inhibitors were synthesized as of the 1970s, but low efficacy or the lack of oral
availability or high cost of synthesis always prevented renin inhibitors from becoming successful drugs.
H
N
H3 C-H 2C-OOC
Imidapril
O
COOH
N
O
N
(4S)-3-[(2S)-2[[1-(Ethoxycarbonyl)-3-phenylpropyl]-amino]-1-oxopropyl]-1-methyl-2-oxo-imidazolidine
-4-carboxylic acid
2(S),4(S),5(S),7(S)-N-(2-carbamoyl-2-methylpropyl)-5-amino-4-hydroxy-2,7-diisopropyl-8-[4-methoxy-3-(3-methoxypropoxy-)phenyl]octanamid hemifumarate
Most prescribed classes of antihypertensive drugs (US)
Beta blockers and ACE inhibitors account for 58% of all antihypertensives prescribed in the US.