Therapeutic drugs during healing after myocardial infarction modify infarct collagens and ventricular distensibility at elevated pressures

We investigated whether therapeutic drugs given during healing following acute myocardial infarction (AMI) modify infarct collagens and left ventricular (LV) distensibility. We treated dogs with drugs from major classes (i.e., indomethacin, ibuprofen, captopril, enalapril, verapamil, amlodipine, propranolol, isosorbide dinitrate [ISDN] and digoxin) between day 2 and 6 weeks and measured hemodynamics, LV remodeling and function during healing over 6 weeks after transmural anterior AMI, and regional collagens, LV distensibility under increasing pressure, rupture threshold (RT), and topography at 6 weeks. Relative to sham, AMI controls showed infarct zone (IZ) expansion and thinning, 9.3-fold increase in IZ collagen, LV dilation and dysfunction, and no change in distensibility and RT. Relative to controls, indomethacin as well as enalapril, captopril and amlodipine decreased IZ collagen. Infarct expansion was attenuated by ibuprofen, captopril, amlodipine and ISDN but augmented by indomethacin. Infarct thinning was prevented by captopril, amlodipine and ISDN but enhanced by indomethacin. Importantly, indomethacin and enalapril enhanced LV distensibility and lowered RT. Distensibility correlated positively with IZ type III collagen and negatively with type I/III collagen ratio and pyridinoline cross-links whereas RT correlated positively with IZ type I collagen. Systolic volume and ejection fraction deteriorated with indomethacin but were improved or preserved with other therapies. The results demonstrate that different therapeutic drugs may produce different effects on IZ collagens during healing post-AMI: drugs that attenuate or adversely alter IZ collagens also enhance LV distensibility, augment adverse remodeling and lower RT, suggesting that testing for these effects post-AMI is warranted.     

Isothiocyanates sensitize the effect of chemotherapeutic drugs via modulation of protein kinase C and telomerase in cervical cancer cells

We determined effects of the vasopeptidase inhibitor (VPI) omapatrilat and angiotensin II type 1 receptor (AT(1)R) blocker (ARB) candesartan in rats during healing between day-2 and day-21 after reperfused myocardial infarction (RMI) on left ventricular (LV) remodeling and function, and regional matrix metalloproteinase (MMP)-9, tissue inhibitor of MMP (TIMP)-3, inducible-nitric-oxide-synthase (iNOS), oxidant-generating myeloperoxidase (MPO), and cytokines tumor-necrosis-factor (TNF)-alpha, interleukin (IL)-6 and IL-10, and transforming-growth-factor (TGF)-beta(1), and collagens. Compared to RMI-placebo, both agents reversed adverse LV remodeling and systolic and diastolic dysfunction, improved collagen remodeling, and normalized MMP-9 (activity, protein, and mRNA), TIMP-3 (protein and mRNA), and iNOS, MPO, TNF-alpha, IL-6, and TGF-beta(1) proteins, and improved MMP-9/TIMP-3 balance and IL-10 levels in previously ischemic zones. The results suggest that modulation of matrix proteases, oxidants, cytokines, and NOSs with omapatrilat and candesartan contribute to reversal of adverse collagen and LV remodeling and attenuation of LV dysfunction during healing after RMI.     

AT1 receptor blockade alters metabolic, functional and structural proteins after reperfused myocardial infarction: detection using proteomics

Angiotensin II (AngII) type 1 receptor (AT1R) blockers (ARBs) limit left ventricular (LV) dysfunction and necrosis after reperfused myocardial infarction (RMI) and proteomics can detect changes in protein levels after injury. We applied proteomics to detect changes in levels of specific protein in the ischemic zone (IZ) and non-ischemic zone (NIZ) of dog hearts after in vivo RMI (90 min of anterior ischemia; 120 min of reperfusion) and treatment with intravenous vehicle (control) and the ARBs valsartan or irbesartan (10 mg/kg) over 30 min before RMI. We also assessed LV function, infarction and apoptosis. Both ARBs limited the RMI-induced LV dysfunction, infarct size and apoptosis. Proteomics detected differential expression of 5 randomly selected proteins in the IZ compared to the NIZ after RMI: decrease in a subunit of ATP synthase isoform precursor (consistent with increased conversion to a subunit under metabolic stress), M chain creatine kinase (consistent with cellular damage) and ventricular myosin light chain-1 (consistent with structural damage and decreased contractility); and increase in NAD+ -isocitrate dehydrogenase (ICDH) and alpha subunit and ATP synthase D chain (mitochondrial, consistent with metabolic dysfunction). Importantly, changes in NAD+ -ICDH and ATP synthase D chain were reversed by ARB therapy. Thus, proteomics can detect regional changes in metabolic, contractile, and structural proteins after RMI and several of these proteins are favorably modified by ARBs, suggesting that they may be novel therapeutic targets.     

Collagen gene expression in rat left ventricle: interactive effect of age and exercise training.

Whether or not exercise training of sufficient intensity and duration to produce left ventricle (LV) hypertrophy also regulates deposition of interstitial collagen and cross-linking at the pretranslational level is unknown. Therefore, the effects of exercise training on gene expression for the two principal fibrillar collagens in LV, types I and III, were assessed in young adult (5 mo), middle-aged (15 mo), and old (26 mo) rats. We also evaluated the potential interaction of changes in mRNA for these procollagens with alterations in LV extracellular matrix characteristics by simultaneously measuring collagen concentration (hydroxyproline) and extent of mature collagen cross-linking (hydroxylysylpyridinoline, HP). Ten weeks of treadmill running resulted in LV hypertrophy and an increased maximal oxygen uptake in all three age groups of trained rats compared with sedentary controls. Percent collagen in rat LV almost doubled (P < 0.0001) from 5 to 26 mo of age, an increase unaffected by exercise training. With aging, a significant decline in expression of mRNAs for both collagen type I (P < 0.005) and type III (P < 0.001) was observed in LV free wall (LVF) but not septum (LVS). Training prevented this decline in LVF mRNAs for the two principal fibrillar collagens in middle-aged rats whereas it attenuated the decline in senescent animals. HP concentration increased significantly with aging in both LVF (P < 0.005) and LVS (P < 0.01). Training modulated this effect, but again only in LVF, so that HP was significantly lower (P < 0.05) in this region of the LV in old trained rats compared with sedentary counterparts. We conclude that exercise training modulates the effects of aging on collagen gene mRNAs and HP cross-linking regionally within the LV.     

Role of healing-specific-matricellular proteins and matrix metalloproteinases in age-related enhanced early remodeling after reperfused STEMI in dogs

We assessed whether aging augments left ventricular (LV) damage, remodeling, and dysfunction and alters expression of healing-specific-matricellular proteins (HSMPs), matrix metalloproteinases (MMPs) and other pertinent proteins after acute reperfused-ST-segment-elevation myocardial infarction (RSTEMI) in the dog model. The findings suggest a novel role for HSMPs, MMPs, and the other proteins in the age-related increase in LV damage, remodeling, and dysfunction. Potentially detrimental effects of the altered proteins appear to outweigh beneficial effects and contribute to adverse outcome. Deleterious changes include the increase in matrix-degrading MMPs, inducible nitric oxide synthase (iNOS) and pro-inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, HSMPs such as secreted-protein-acidic-and-rich-in-cysteine (SPARC) and osteopontin (OPN), the blunted increase in endothelial-NOS (eNOS), and the decrease in IL-10 and neuronal NOS (nNOS). Potentially beneficial changes include increases in the HSMP secretory-leucocyte-protease-inhibitor (SLPI) and cytokine transforming growth factor (TGF)-beta(1). Targeting these proteins may mitigate enhanced LV remodeling and dysfunction with aging.     

Valsartan reverses post-translational modifications of the delta-subunit of ATP synthase during in vivo canine reperfused myocardial infarction

To determine whether reperfused myocardial infarction (RMI) induces PTM of the delta-subunit of the mitochondrial metabolic enzyme ATP synthase (ATP/delta) in the ischemic zone (IZ) and whether this can be reversed by the angiotensin II type 1 receptor (AT(1)R) blocker valsartan, we applied a pharmaco-proteomics approach in canine RMI hearts with or without valsartan pretreatment. Using the 2-DE technique, we identified differential regional expression of ATP/delta in the IZ compared to the non-ischemic zone (NIZ), with an approximately 2-fold increase in the IZ that was normalized by valsartan. Furthermore in the IZ, RMI triggered S-nitrosylation of cysteine-100, nitration of the two tyrosines 88 and 225, and hydroxylation of lysine-182 in ATP/delta followed by its myristoylation. Importantly, valsartan abolished these modifications of ATP/delta in the IZ, triggered phosphorylation of serine-76 in both the IZ and NIZ, and decreased necrosis, apoptosis, left ventricular dysfunction and remodeling. Thus, AT(1)R-blocker-induced cardioprotection during RMI is associated with phosphorylation of ATP/delta and inhibition of nitric oxide-related chemical modifications such as S-nitrosylation, nitration and hydroxylation. Targeting specific PTMs during RMI, such as those of ATP/delta with AT(1)R blockade, might be a potentially powerful novel therapeutic approach. However, the identification of S-nitrosylation was putative and requires MS/MS verification.     

Chronic beta-adrenoreceptor activation increases cardiac cavity size through chamber remodeling and not via modifications in myocardial material properties

Chronic beta-adrenoreceptor (beta-AR) activation increases left ventricular (LV) cavity size by promoting a rightward shift in LV diastolic pressure-volume (P-V) relations in association with increases in low-tensile strength myocardial (non-cross-linked) collagen concentrations. Because diastolic P-V relations are determined by chamber remodeling as well as by myocardial material properties (indexed by myocardial stiffness), both of which are associated with modifications in myocardial collagen cross-linking, we evaluated whether chamber remodeling or alterations in myocardial material properties govern beta-AR-mediated modifications in diastolic P-V relations. The effects of chronic administration of isoproterenol (Iso; 0.04 mg.kg(-1).day(-1) from 12 to 19 mo of age) to spontaneously hypertensive rats (SHRs) on LV cavity dimensions, LV diastolic P-V relations, myocardial collagen characteristics, myocardial stiffness constants [e.g., the slope of the LV diastolic stress-strain relation (k)], and LV chamber and myocardial systolic function were assessed. SHRs at 19 mo of age had normal LV diastolic P-V relations, marked myocardial fibrosis (using a pathological score), increased myocardial cross-linked (insoluble to cyanogen bromide digestion) type I and type III collagen concentrations, and enhanced myocardial k values. Iso administration to SHRs resulted in enlarged LV cavity dimensions mediated by a rightward shift in LV diastolic P-V relations, increased volume intercept of the LV diastolic P-V relation, decreased LV relative wall thickness despite a tendency to augment LV hypertrophy, and increased non-cross-linked type I and type III myocardial collagen concentrations. Iso administration resulted in reduced pump function without modification of intrinsic myocardial systolic function. However, despite increasing myocardial non-cross-linked concentrations, Iso failed to alter myocardial k in SHRs. These results suggest that beta-AR-mediated rightward shifts in LV diastolic P-V relations, which induce decreased pump function, are mediated by chamber remodeling but not by modifications in myocardial material properties.     

AT1receptor blockade alters metabolic,functional and structural proteins after reperfused myocardial infarction: Detection using proteomics

Angiotensin II (AngII) type 1 receptor (AT₁R) blockers (ARBs) limit left ventricular (LV) dysfunction and necrosis after reperfused myocardial infarction (RMI) and proteomics can detect changes in protein levels after injury. We applied proteomics to detect changes in levels of specific protein in the ischemic zone (IZ) and non-ischemic zone (NIZ) of dog hearts after in vivo RMI (90 min of anterior ischemia; 120 min of reperfusion) and treatment with intravenous vehicle (control) and the ARBs valsartan or irbesartan (10 mg/kg) over 30 min before RMI. We also assessed LV function, infarction and apoptosis. Both ARBs limited the RMI-induced LV dysfunction, infarct size and apoptosis. Proteomics detected differential expression of 5 randomly selected proteins in the IZ compared to the NIZ after RMI: decrease in subunit of ATP synthase isoform precursor (consistent with increased conversion to subunit under metabolic stress), M chain creatine kinase (consistent with cellular damage) and ventricular myosin light chain-1 (consistent with structural damage and decreased contractility); and increase in NAD⁺-isocitrate dehydrogenase (ICDH) and subunit and ATP synthase D chain (mitochondrial, consistent with metabolic dysfunction). Importantly, changes in NAD₊-ICDH and ATP synthase D chain were reversed by ARB therapy. Thus, proteomics can detect regional changes in metabolic, contractile, and structural proteins after RMI and several of these proteins are favorably modified by ARBs, suggesting that they may be novel therapeutic targets. (Mol Cell Biochem 263: 179–188, 2004)     

AT2 receptor and apoptosis during AT1 receptor blockade in reperfused myocardial infarction in the rat

We assessed whether upregulation of the angiotensin II (AngII) type 2 receptor (AT2R) during AngII type 1 receptor (AT1R) blockade might induce apoptosis in the in vivo rat model of reperfused myocardial infarction (RMI) and whether addition of an AT2R blocker abolishes that effect. We measured in vivo hemodynamics and left ventricular (LV) systolic and diastolic function (echocardiograms/Doppler), and ex vivo infarct size (triphenyl tetrazolium chloride), regional AT1R and AT2R proteins (immunoblots), and apoptosis (TUNEL assay and DNA ladder) after regional anterior RMI (60 min ischemia, 90 min reperfusion) in Sprague-Dawley rats randomized to intravenous AT1R blockade with candesartan (1 mg/kg, n = 9) or saline (controls, n = 14) over 30 min before RMI, and sham (n = 8). We also assessed the effect of AT2R blockade (PD123319, 10 mg/kg i.v.) plus candesartan on infarct size and apoptosis. Compared to controls, candesartan significantly (p < 0.001) limited increases in left atrial pressure, improved positive LV dP/dtmax and negative dP/dtmin, normalized LV ejection fraction, improved LV diastolic function, limited infarct expansion, decreased infarct size and apoptosis, and increased AT2R protein (not AT1R) in the reperfused ischemic zone. There were no changes in sham hearts. PD123319 abolished the candesartan-induced decrease in infarct size and LV dysfunction but not the decrease in apoptosis. Thus, during AT1R blockade in the in vivo rat model of RMI, regional AT2R upregulation contributes to the beneficial effect on infarct size and LV dysfunction but not on apoptosis, suggesting that the apoptosis is AT1R not AT2R-mediated.     

AT1 receptor antagonism attenuates target organ effects of salt excess in SHRs without affecting pressure

Our recent studies have demonstrated that salt excess in the spontaneously hypertensive rat (SHR) produces a modestly increased arterial pressure while promoting marked myocardial fibrosis and structural damage associated with altered coronary hemodynamics and ventricular function. The present study was designed to determine the efficacy of an angiotensin II type 1 (AT(1)) receptor blocker (ARB) in the prevention of pressure increase and development of target organ damage from high dietary salt intake. Eight-week-old SHRs were given an 8% salt diet for 8 wk; their age- and gender-matched controls received standard chow. Some of the salt-loaded rats were treated concomitantly with ARB (candesartan; 10 mg kg(-1) day(-1)). The ARB failed to reduce the salt-induced rise in pressure, whereas it significantly attenuated left ventricular (LV) remodeling (mass and wall thicknesses), myocardial fibrosis (hydroxyproline concentration and collagen volume fraction), and the development of LV diastolic dysfunction, as shown by longer isovolumic relaxation time, decreased ratio of peak velocity of early to late diastolic waves, and slower LV relaxation (minimum first derivative of pressure over time/maximal LV pressure). Without affecting the increased pulse pressure by high salt intake, the ARB prevented the salt-induced deterioration of coronary and renal hemodynamics but not the arterial stiffening or hypertrophy (pulse wave velocity and aortic mass index). Additionally, candesartan prevented the salt-induced increase in kidney mass index and proteinuria. In conclusion, the ARB given concomitantly with dietary salt excess ameliorated salt-related structural and functional cardiac and renal abnormalities in SHRs without reducing arterial pressure. These data clearly demonstrated that angiotensin II (via AT(1) receptors), at least in part, participated importantly in the pressure-independent effects of salt excess on target organ damage of hypertension.     

Attenuation of increased secretory leukocyte protease inhibitor, matricellular proteins and angiotensin II and left ventricular remodeling by candesartan and omapatrilat during healing after reperfused myocardial infarction

While secretory-leukocyte-protease-inhibitor (SLPI) may promote skin wound healing, its role in infarct healing after reperfused myocardial infarction (RMI) remains unclear. Short-term intravenous angiotensin II (AngII) receptor blocker therapy with candesartan (CN) attenuates increased SLPI and markers of early matrix/left ventricular (LV) in acute RMI. To determine whether reducing effects of AngII with CN or the vasopeptidase inhibitor omapatrilat (OMA) during the healing phase after RMI attenuates SLPI and other mediators of healing and matrix/LV remodeling, we measured these in Sprague–Dawley rats randomized to oral placebo, CN (30 mg/kg/day) or OMA (10 mg/kg/day) therapy during healing between days 2 and 23 after RMI and sham. On day-25, RMI-placebo showed significant LV remodeling, systolic/diastolic dysfunction and impaired passive compliance, and ischemic zone increases in SLPI, secreted-protein-acidic-and-rich-in-cysteine (SPARC) and osteopontin (OPN) mRNA and protein. In addition, metalloproteinase (MMP)-9 and -2, a-disintegrin-and-metalloproteinase (ADAM)-10 and -17, inducible-nitric-oxide-synthase (iNOS), pro-inflammatory cytokines interleukin (IL)-6, and tumor necrosis factor-α, transforming growth factor (TGF)-β₁ and its signaling molecule p-Smad-2, myeloperoxidase (MPO), AngII, MPO-positive granulocytes, MAC387-positive macrophages and monocytes, scar collagens, cardiomyocyte and fibroblast apoptosis, and microvascular no-reflow also increased whereas anti-inflammatory cytokine IL-10 decreased. Both CN and OMA attenuated all the changes except IL-10, which normalized. Thus, CN or OMA treatment during healing after RMI results in attenuation of SLPI as well as tissue AngII and mediators of inflammation and matrix/LV remodeling including SPARC, OPN, and ADAMs. Whether increasing SLPI on top of background AngII inhibition or therapy such as CN or OMA might produce added remodeling benefit needs study.     

Detection of regional changes in protein levels in the in vivo canine model of acute heart failure following ischemia-reperfusion injury: functional proteomics studies

In this study, we demonstrate the use of proteomics to detect regional differences in protein levels between the reperfused ischemic zone (IZ) and the nonischemic zone (NIZ) of dog hearts which were subjected to in vivo ischemia-reperfusion injury. Using the two-dimensional gel electrophoresis (2-DE) technique, we identified five proteins that were differentially expressed in the IZ versus NIZ: (1) the alpha subunit of ATP synthase isoform precursor was decreased 1.71-fold; (2) creatine kinase M chain was decreased 1.72-fold; (3) NAD+-isocitrate dehydrogenase, alpha subunit was increased 8.34-fold; (4) ATP synthase D chain, mitochondrial was increased 3.02-fold; (5) ventricular myosin light chain-1 was decreased 2.02-fold. Additionally, we found that the level of actin was decreased 2.6-times in the IZ compared to the NIZ on Western blot analysis but was unchanged on 2-DE.     

Modification of myosin protein and gene expression in failing hearts due to myocardial infarction by enalapril or losartan

The effects of enalapril, an angiotensin converting enzyme (ACE) inhibitor, and losartan, an angiotensin II receptor type I antagonist, were investigated on alterations in myofibrillar ATPase activity as well as myosin heavy chain (MHC) content and gene expression in failing hearts following myocardial infarction (MI). Three weeks after ligation of the left coronary artery, rats were treated with or without enalapril (10 mg/kg/day), and/or losartan (20 mg/kg/day) for 5 weeks. The infarcted animals exhibited an increase in left ventricle (LV) end diastolic pressure and depressed rates of LV pressure development as well as pressure decay. LV myofibrillar Ca2+ -stimulated ATPase activity was decreased in the infarcted hearts compared with controls, MHC alpha-isoform content was significantly decreased whereas that of MHC beta-isoform was markedly increased. The level of MHC alpha-isoform mRNA was decreased whereas that of MHC beta-isoform was increased in the viable infarcted LV. Treatment of animal with enalapril, losartan, or combination of enalapril and losartan partially prevented the MI induced changes in LV function, myofibrillar Ca2+ -stimulated ATPase activity, MHC protein expression and MHC gene expression. The results suggest that the beneficial effects of the renin-angiotensin system blockade in heart failure are associated with partial prevention of myofibrillar remodeling.     

Ventricular remodeling: insights from pharmacologic interventions with angiotensin-converting enzyme inhibitors

Structural remodeling of the left ventricular (LV) myocardium develops in a time-dependent fashion following acute myocardial infarction and may be an integral component in the transition toward overt heart failure. Globally, the remodeling process is characterized by progressive LV enlargement and increased chamber sphericity. At the cellular level, the remodeling process is associated with myocyte slippage, hypertrophy, and accumulation of collagen in the interstitial compartment. In the present study, we examined the effects of early, long-term monotherapy with the angiotensin converting enzyme (ACE) inhibitor, enalapril, on the progression of LV remodeling in dogs with LV dysfunction (ejection fractions 30–40%) produced by multiple sequential intracoronary microembolizations. Dogs were randomized to 3 months oral therapy with enalapril (n=7) or to no treatment (n=7). In untreated dogs, LV end-systolic volume index (ESVI), end-diastolic volume index (EDVI) and chamber sphericity increased significantly during the 3 months follow-up period. In contrast, in dogs treated with enalapril ESVI, EDVI and chamber sphericity remained essentially unchanged. Treatment with enalapril attenuated myocyte hypertrophy and the accumulation of interstitial collagen in comparison to untreated dogs. These data indicate that early treatment with ACE inhibitors can prevent the progression of LV remodeling in dogs with LV dysfunction. Afterload reduction, inhibition of direct action of angiotensin-II and possibly the decrease in bradykinin degradation elicited by ACE inhibition may act in concert in preventing the progression LV chamber remodeling.     

Selective type 1 angiotensin II receptor blockade attenuates oxidative stress and regulates angiotensin II receptors in the canine failing heart

Background and objective Angiotensin II type 1 receptor (AT₁R) blockade reduces vascular oxidative stress but whether myocardial oxidative stress represents a mechanism for the beneficial effect of AT₁R blockade in heart failure is unclear. Furthermore, the impact of AT₁R blockade on the expression of angiotensin II receptors in heart failure has not been well documented. Accordingly, we examined the impact of the AT₁R blocker candesartan on hemodynamics, left ventricular (LV) remodeling (echocardiography), oxidative stress, and tissue expression of AT₁Rs and angiotensin II type 2 receptors (AT₂Rs) in a canine model of pacing-induced heart failure. Methods and results Animals were randomized to rapid right ventricular-pacing (250 beats/min for 3 weeks) to severe heart failure and treated with candesartan (10 mg/kg daily, n = 8) or placebo (n = 8) from day 3 onwards, or no pacing (sham, n = 7). Candesartan significantly reduced mean pulmonary arterial and LV diastolic pressure, LV end-diastolic and end-systolic volume and ascites, increased cardiac output, dP/dt, and ejection fraction, while reversing the marked increase in aldehydes, a marker of oxidative stress, observed in the placebo group. Although candesartan did not alter LV AT₁R protein expression compared to placebo or sham, it reversed the decrease in AT₂R protein observed in the placebo group. Conclusion Our results indicate that in the pacing model of heart failure, chronic AT₁R blockade attenuates hemodynamic deterioration and limits LV remodeling and dysfunction, in part by reversing oxidative stress and AT₂R downregulation.     

Diastolic wall stress and ANG II in cardiac hypertrophy and gene expression induced by volume overload

We investigated the effects of diastolic wall stress (WS) and angiotensin II (ANG II) on the left ventricular (LV) hypertrophy (LVH) induced by volume overload and on the gene expression of LV adrenomedullin (AM) and atrial natriuretic peptide (ANP) in volume overload. Diastolic WS was pharmacologically manipulated with (candesartan) or without (calcium channel blocker manidipine) inhibition of ANG II type 1 receptors in aortocaval-shunted rats over 6 wk. Diastolic WS reached a plateau at 2 wk and subsequently declined regardless of further LVH. Although diastolic WS was decreased to a similar extent by both compounds, candesartan blunted LVH over 6 wk, whereas manidipine blunted LVH at 2 wk but not after 4 wk. Levels of AM and ANP gene expression increased as LVH developed but were completely suppressed by candesartan over 6 wk. ANP expression level was also attenuated by manidipine over 6 wk, whereas AM expression level was suppressed at 2 wk but not after 4 wk by manidipine. We concluded that diastolic WS and ANG II might be potent stimuli for the LVH and LV AM and ANP gene expression in volume overload and that diastolic WS could be relatively involved in the early LVH and in the gene expression of ANP rather than of AM.     

The vitamin D receptor activator paricalcitol prevents fibrosis and diastolic dysfunction in a murine model of pressure overload

BACKGROUND: Activation of the vitamin D-vitamin D receptor (VDR) axis has been shown to reduce blood pressure and left ventricular (LV) hypertrophy. Besides cardiac hypertrophy, cardiac fibrosis is a key element of adverse cardiac remodeling. We hypothesized that activation of the VDR by paricalcitol would prevent fibrosis and LV diastolic dysfunction in an established murine model of cardiac remodeling. METHODS: Mice were subjected to transverse aortic constriction (TAC) to induce cardiac hypertrophy. Mice were treated with paricalcitol, losartan, or a combination of both for a period of four consecutive weeks. RESULTS: The fixed aortic constriction caused similar increase in blood pressure, both in untreated and paricalcitol- or losartan-treated mice. TAC significantly increased LV weight compared to sham operated animals (10.2±0.7 vs. 6.9±0.3mg/mm, p<0.05). Administration of either paricalcitol (10.5±0.7), losartan (10.8±0.4), or a combination of both (9.2±0.6) did not reduce LV weight. Fibrosis was significantly increased in mice undergoing TAC (5.9±1.0 vs. sham 2.4±0.8%, p<0.05). Treatment with losartan and paricalcitol reduced fibrosis (paricalcitol 1.6±0.3% and losartan 2.9±0.6%, both p<0.05 vs. TAC). This reduction in fibrosis in paricalcitol treated mice was associated with improved indices of LV contraction and relaxation, e.g. dPdtmax and dPdtmin and lower LV end diastolic pressure, and relaxation constant Tau. Also, treatment with paricalcitol and losartan reduced mRNA expression of ANP, fibronectin, collagen III and TIMP-1. DISCUSSION: Treatment with the selective VDR activator paricalcitol reduces myocardial fibrosis and preserves diastolic LV function due to pressure overload in a mouse model. This is associated with a reduced percentage of fibrosis and a decreased expression of ANP and several other tissue markers.     

Both enalapril and losartan attenuate sarcolemmal Na+-K+-ATPase remodeling in failing rat heart due to myocardial infarction

To investigate the mechanisms underlying the depressed sarcolemmal (SL) Na(+)-K(+)-ATPase activity in congestive heart failure (CHF), different isoforms and gene expression of Na(+)-K(+)-ATPase were examined in the failing left ventricle (LV) at 8 weeks after myocardial infarction (MI). In view of the increased activity of renin-angiotensin system (RAS) in CHF, these parameters were also studied after 5 weeks of treatment with enalapril (10 mg x kg-1 x day-1), an angiotensin-converting enzyme inhibitor, and losartan (20 mg.kg-1.day-1), an angiotensin II type 1 receptor antagonist, starting at 3 weeks after the coronary ligation in rats. The infarcted animals showed LV dysfunction and depressed SL Na(+)-K(+)-ATPase activity. Protein content and mRNA levels for Na(+)-K(+)-ATPase alpha2 isoform were decreased whereas those for Na(+)-K(+)-ATPase alpha3 isoform were increased in the failing LV. On the other hand, no significant changes were observed in protein content or mRNA levels for Na(+)-K(+)-ATPase alpha1 and beta1 isoforms. The treatment of infarcted animals with enalapril or losartan improved LV function and attenuated the depression in Na(+)-K(+)-ATPase alpha2 isoform as well as the increase in alpha3 isoform, at both the protein and mRNA levels; however, combination therapy with enalapril and losartan did not produce any additive effects. These results provide further evidence that CHF due to MI is associated with remodeling of SL membrane and suggest that the blockade of RAS plays an important role in preventing these alterations in the failing heart.     

Quantitative and metabolic changes of hepatic collagens in rats after carbon tetrachloride poisoning

1. The collagen hydroxyproline in rat liver was composed of 3.5% neutral-soluble collagen, 4.9% acid-soluble collagen and 91.6% insoluble collagen. In labelling studies with [(14)C]proline in vitro, the specific radioactivities of neutral-soluble, acid-soluble and insoluble collagens in rat liver were found to be 233000, 69000 and 830d.p.m./mumol of hydroxyproline respectively after 1h. 2. During subacute carbon tetrachloride poisoning the hepatic content of insoluble collagen markedly increased, whereas those of soluble collagens did not change. During recovery from subacute poisoning hepatic contents of soluble collagens were markedly decreased. 3. After 8 weeks of carbon tetrachloride poisoning the specific radioactivities of hepatic soluble collagens increased, while that of insoluble collagen decreased. During recovery from subacute poisoning, the specific radioactivities of soluble collagens decreased to the normal range and that of insoluble collagen further decreased. 4. Hepatic collagenolytic activity solubilizing insoluble collagen, which differs from mammalian collagenase, decreased under the conditions of the subacute poisoning and also during recovery from subacute poisoning.