geranylgeranylacetone and Atrial-Fibrillation

The heat shock protein (HSP) inducer, geranylgeranylacetone (GGA), was previously found to protect against atrial fibrillation (AF) remodeling in experimental model systems. Clinical application of GGA in AF is limited, due to low systemic concentrations owing to the hydrophobic character of GGA.. To identify novel HSP-inducing compounds, with improved physicochemical properties, that prevent contractile dysfunction in experimental model systems for AF.. Eighty-one GGA-derivatives were synthesized and explored for their HSP-inducing properties by assessment of HSP expression in HL-1 cardiomyocytes pretreated with or without a mild heat shock (HS), followed by incubation with 10 µM GGA or GGA-derivative. Subsequently, the most potent HSP-inducers were tested for preservation of calcium transient (CaT) amplitudes or heart wall contraction in pretreated tachypaced HL-1 cardiomyocytes (with or without HSPB1 siRNA) and. Thirty GGA-derivatives significantly induced HSPA1A expression after HS, and seven showed exceeding HSPA1A expression compared to GGA. GGA and nine GGA-derivatives protected significantly from tachypacing (TP)-induced CaT loss, which was abrogated by HSPB1 suppression. GGA and four potent GGA-derivatives protected against heart wall dysfunction after TP compared to non-paced control. We identified novel GGA-derivatives with improved physicochemical properties compared to GGA. GGA-derivatives, particularly GGA

Topics: Animals; Atrial Fibrillation; Diterpenes; Dose-Response Relationship, Drug; Drosophila; Drug Evaluation, Preclinical; Heat-Shock Proteins; Molecular Structure; Myocytes, Cardiac; Structure-Activity Relationship

Atrial Fibrillation (AF) is the most common progressive tachyarrhythmia. AF progression is driven by abnormalities in electrical impulse formation and contractile function due to structural remodeling of cardiac tissue. Previous reports indicate that structural remodeling is rooted in derailment of protein homeostasis (proteostasis). Heat shock proteins (HSPs) play a critical role in facilitating proteostasis. Hence, the HSP-inducing compound geranylgeranylacetone (GGA) and its derivatives protect against proteostasis derailment in experimental models for AF. Whether these compounds also accelerate reversibility from structural remodeling in tachypaced cardiomyocytes is unknown.. To investigate whether the potent HSP inducer GGA*-59 restores structural remodeling and contractile dysfunction in tachypaced cardiomyocytes and explore the underlying mechanisms.. HL-1 cardiomyocytes post-treated with GGA*-59 or recombinant HSPB1 (rcHSPB1) revealed increased levels of HSPB1 expression and accelerated recovery from tachypacing (TP)-induced calcium transient (CaT) loss compared to non-treated cardiomyocytes. In addition, protein levels of the microtubule protein (acetylated) α-tubulin, and contractile proteins cardiac troponin I (cTnI) and troponin T (cTnT) were reduced after TP and significantly recovered by GGA*-59 or rcHSPB1 post-treatment. The mRNA levels of α-tubulin encoding genes, but not cardiac troponin genes, were reduced upon TP and during recovery, but significantly enhanced by GGA*-59 and rcHSPB1 post-treatment. In addition, TP increased calpain activity, which remained increased during recovery and GGA*-59 post-treatment. However, HDAC6 activity, which deacetylates α-tubulin resulting in microtubule disruption, was significantly increased after TP and during recovery, but normalized to control levels by GGA*-59 or rcHSPB1 post-treatment in HL-1 cardiomyocytes.. Our results imply that the HSP inducer GGA*-59 and recombinant HSPB1 accelerate recovery from TP-induced structural remodeling and contractile dysfunction in HL-1 cardiomyocytes. GGA*-59 increases HSPB1 levels, represses HDAC6 activity and restores contractile protein and microtubule levels after TP, indicating that HSP-induction is an interesting target to accelerate recovery from AF-induced remodeling.

Topics: Animals; Atrial Fibrillation; Atrial Remodeling; Cells, Cultured; Diterpenes; Mice; Microtubules; Models, Theoretical; Muscle Contraction; Myocardial Contraction; Myocytes, Cardiac; Proteostasis

Geranylgeranylacetone (GGA) has been reported up-regulating heat shock protein (HSP) expression, and protecting against atrial remodeling. This study aimed to investigate the effects of GGA on atrial electrophysiology and inducibility of atrial fibrillation (AF) in heart failure (HF) model.. HF rabbits were created 4 weeks after coronary artery ligation. Monophasic action potential recordings and multielectrode array were used to record the electrophysiological characteristics of left atrium (LA) in normal, or HF rabbits with (HF-GGA) and without (HF-control) oral administration of GGA (200 mg/kg, 24 h before experiments). The mRNA and protein expressions of ionic channels were measured by Western blot and PCR. HF-GGA LA (n = 10), similar to normal LA (n = 10) had a shorter action potential duration (APD) and effective refractory period than HF-control LA (n = 10). HF-GGA LA had less triggered activity and APD alternans (20% vs. 100%, P = 0.001), lower maxima slope of restitution curve of APD (0.94 ± 0.04 vs.1.69 ± 0.04, P < 0.001), and less inducibility of AF (50% vs. 100%, P = 0.033) than HF-control LA. HF-GGA LA had a shorter activation time and higher conduction velocity than HF-control LA. HF-GGA LA had a higher mRNA expression of Cav1.2, Nav1.5, Kir2.1, Kv1.4, Kv7.1, Kv11.1, sarcoplasmic reticulum Ca(2+)-ATPase, and higher phosphorylation of phospholamban than HF-control LA.. GGA decreases triggered activity, dispersion of APD and inducibility of AF in failing heart through induction of HSP, and modulation of ionic channels and calcium homeostasis.

Topics: Action Potentials; Animals; Atrial Fibrillation; Diterpenes; Heart Failure; Heat-Shock Proteins; Rabbits

The most common clinical tachycardia, Atrial Fibrillation (AF), is a progressive disease, caused by cardiomyocyte remodeling, which finally results in contractile dysfunction and AF persistence. Recently, we identified a protective role of heat shock proteins (HSPs), especially the small HSPB1 member, against tachycardia remodeling in experimental AF models. Our understanding of tachycardia remodeling and anti-remodeling drugs is currently hampered by the lack of suitable (genetic) manipulatable in vivo models for rapid screening of key targets in remodeling. We hypothesized that Drosophila melanogaster can be exploited to study tachycardia remodeling and protective effects of HSPs by drug treatments or by utilizing genetically manipulated small HSP-overexpressing strains. Tachypacing of Drosophila pupae resulted in gradual and significant cardiomyocyte remodeling, demonstrated by reduced contraction rate, increase in arrhythmic episodes and reduction in heart wall shortening, compared to normal paced pupae. Heat shock, or pre-treatment with HSP-inducers GGA and BGP-15, resulted in endogenous HSP overexpression and protection against tachycardia remodeling. DmHSP23 overexpressing Drosophilas were protected against tachycardia remodeling, in contrast to overexpression of other small HSPs (DmHSP27, DmHSP67Bc, DmCG4461, DmCG7409, and DmCG14207). (Ultra)structural evaluation of the tachypaced heart wall revealed loss of sarcomeres and mitochondrial damage which were absent in tachypaced DmHSP23 overexpressing Drosophila. In addition, tachypacing induced a significant increase in calpain activity, which was prevented in tachypaced Drosophila overexpressing DmHSP23. Tachypacing of Drosophila resulted in cardiomyocyte remodeling, which was prevented by general HSP-inducing treatments and overexpression of a single small HSP, DmHSP23. Thus, tachypaced D. melanogaster can be used as an in vivo model system for rapid identification of novel targets to combat AF associated cardiomyocyte remodeling.

Topics: Animals; Atrial Fibrillation; Calpain; Disease Models, Animal; Diterpenes; Drosophila melanogaster; Drosophila Proteins; Gene Expression; Gene Expression Regulation; Heart; Heat-Shock Proteins; Heat-Shock Proteins, Small; Myocardial Contraction; Oximes; Piperidines; Tachycardia

Atrial fibrillation (AF) is the commonest arrhythmia. Studies have shown that atrial tachypacing (artificial persistent AF) causes electrical remodelling. This is characterised by the shortening of the atrial effective refractory period (ERP), in which reduction in L-type Ca(2+) channel current plays an essential part. Atrial fibrosis, a feature of structural remodelling, is induced by continuous infusion of angiotensin II, and has been associated with conduction delay in atria, which promotes AF. Acute atrial ischaemia, frequently observed during development of acute coronary syndrome, has been associated with atrial conduction heterogeneity, which also promotes AF. Induction of heat shock proteins (Hsp72 and Hsp27) by hyperthermia and/or geranylgeranylacetone has demonstrated to protect the heart against such atrial remodelling. The potent protective role of Hsp72 and Hsp27 against clinical AF in patients who underwent open heart surgery has been shown. Taken together, interventions that induce heat shock responses (including induction of Hsp72 and Hsp27) may prevent newly developed AF and delay the progression of paroxysmal AF to persistent AF.

Topics: Animals; Atrial Fibrillation; Diterpenes; Dogs; Fever; Fibrosis; Heart Atria; HSP27 Heat-Shock Proteins; HSP72 Heat-Shock Proteins; Humans

Heat shock proteins (HSPs) are a set of endogenous cytoprotective factors activated by various pathological conditions. This study addressed the effects of geranylgeranylacetone (GGA), an orally active HSP inducer, on the atrial fibrillation (AF) substrate associated with acute atrial ischaemia (AI).. Four groups of mongrel dogs were studied: (1) a group subjected to AI without GGA (AI-CTL, n = 13 dogs); (2) dogs that underwent AI after GGA pretreatment (120 mg/kg/day; AI-GGA, n = 12); (3) dogs receiving GGA pretreatment without AI (n = 5); (4) control dogs for tissue sampling (n = 5). Isolated right AI was produced by occluding a right atrial (RA) coronary-artery branch. AI reduced ischaemic-zone conduction velocity (CV, from 94 +/- 3 to 46 +/- 5 cm/s; P < 0.01) and increased maximum local phase delays (P95, from 1.6 +/- 0.1 to 4.6 +/- 0.6 ms/mm; P < 0.01), conduction heterogeneity index (CHI, from 0.7 +/- 0.1 to 2.9 +/- 0.5; P < 0.01), and the mean duration of burst pacing-induced AF (DAF, from 44 +/- 18 to 890 +/- 323 s; P < 0.01) in AI-CTL dogs. GGA pretreatment attenuated ischaemia-induced conduction abnormalities (CV, 77 +/- 8 cm/s; P95, 2.1 +/- 0.4 ms/mm; CHI, 1.1 +/- 0.2; all P < 0.01 vs. AI-CTL) and DAF (328 +/- 249 s; P < 0.01) in AI-GGA dogs. GGA treatment alone, without ischaemia, did not alter DAF or conduction indices. AI slightly prolonged atrial refractory period, an effect also prevented by GGA. GGA significantly increased HSP70 protein expression in RA tissues of ischaemic hearts.. GGA prevents ischaemia-induced atrial conduction abnormalities and suppresses ischaemia-related AF. These results suggest that HSP induction might be a useful new anti-AF intervention for patients with coronary artery disease.

Topics: Action Potentials; Administration, Oral; Animals; Anti-Arrhythmia Agents; Atrial Fibrillation; Disease Models, Animal; Diterpenes; Dogs; Heart Atria; Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Myocardial Ischemia; Myocardium; Time Factors; Up-Regulation

Atrial fibrillation (AF) causes myocyte stress by inducing structural changes, predominantly myolysis, which is related to the progression of AF. As heat shock proteins (Hsp) protect against cellular stress, their efficacy in preventing myolysis was investigated in a tachy-paced cell model for AF and in patients with AF. HL-1 atrial myocytes were subjected to tachy-pacing, which induced myolysis. Hsp overexpression was accomplished by a mild heat shock or by the drug geranylgeranylacetone (GGA). Hsp-gene-transfection studies were carried out to investigate roles of individual Hsp. In left and/or right atrial appendages from patients with paroxysmal (n=14), persistent (n=17) AF and controls (n=13) in sinus rhythm (SR), Hsp levels (Westerns) and localization (confocal microscopy) were determined. Heat shock and GGA administered prior to tachy-pacing resulted in almost complete protection against tachy-pacing-induced myolysis. Overexpression of Hsp27, but not of Hsp70, also provided complete protection against pacing-induced myolysis. In patients with paroxysmal AF, Hsp27 expression was significantly increased compared to SR and persistent AF. No changes in Hsp40, Hsc70, Hsp70 and Hsp90 expression levels were observed. Hsp27 levels correlated inversely with the duration of paroxysmal and persistent AF and the extent of myolysis. Furthermore, Hsp27 was localized on myofibrils in tachy-paced HL-1 myocytes and in human cardiomyocytes. These data demonstrate that upregulation of Hsp, especially Hsp27, protects tachy-paced atrial myocytes from myolysis. Therefore, the observed elevated Hsp27 expression in patients with paroxysmal AF might serve to protect myocytes from myolysis and limit the progression to persistent AF. Pharmacological induction of Hsp, with drugs such as GGA, may represent a novel therapeutic approach in AF.

Topics: Aged; Animals; Atrial Appendage; Atrial Fibrillation; Diterpenes; Heart Diseases; Heat-Shock Proteins; HSP27 Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Humans; Mice; Middle Aged; Molecular Chaperones; Myocytes, Cardiac; Neoplasm Proteins; Time Factors; Up-Regulation

There is evidence suggesting that heat shock proteins (HSPs) may protect against clinical atrial fibrillation (AF). We evaluated the effect of HSP induction in an in vitro atrial cell line (HL-1) model of tachycardia remodeling and in tachypaced isolated canine atrial cardiomyocytes. We also evaluated the effect of HSP induction on in vivo AF promotion by atrial tachycardia-induced remodeling in dogs. Tachypacing (3 Hz) significantly and progressively reduced Ca(2+) transients and cell shortening of HL-1 myocytes over 4 hours. These reductions were prevented by HSP-inducing pretreatments: mild heat shock, geranylgeranylacetone (GGA), and transfection with human HSP27 or the phosphorylation-mimicking HSP27-DDD. However, treatment with HSP70 or the phosphorylation-deficient mutant HSP27-AAA failed to alter tachycardia-induced Ca(2+) transient and cell-shortening reductions, and downregulation (short interfering RNA) of HSP27 prevented GGA-mediated protection. Tachypacing (3 Hz) for 24 hours in vitro significantly reduced L-type Ca(2+) current and action potential duration in canine atrial cardiomyocytes; these effects were prevented when tachypacing was performed in cells exposed to GGA. In vivo treatment with GGA increased HSP expression and suppressed refractoriness abbreviation and AF promotion in dogs subjected to 1-week atrial tachycardia-induced remodeling. In conclusion, our findings indicate that (1) HSP induction protects against atrial tachycardia-induced remodeling, (2) the protective effect in HL-1 myocytes requires HSP27 induction and phosphorylation, and (3) the orally administered HSP inducer GGA protects against AF in a clinically relevant animal model. These findings advance our understanding of the biochemical determinants of AF and suggest the possibility that HSP induction may be an interesting novel approach to preventing clinical AF.

Topics: Animals; Atrial Fibrillation; Cardiotonic Agents; Diterpenes; Dogs; Heart Atria; Heat-Shock Proteins; Heat-Shock Response; HSP27 Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Humans; Molecular Chaperones; Myocardial Contraction; Myocytes, Cardiac; Neoplasm Proteins; Pacemaker, Artificial; Patch-Clamp Techniques; Phosphorylation; RNA, Small Interfering; Transfection