Jennifer W. Hendrick

Selective Targeting and Timing of Matrix Metalloproteinase Inhibition in Post-Myocardial Infarction Remodeling

Background—A cause-and-effect relationship exists between matrix metalloproteinase (MMP) induction and left ventricular (LV) remodeling after myocardial infarction (MI). Whether broad-spectrum MMP inhibition is necessary and the timing at which MMP inhibition should be instituted after MI remain unclear. This study examined the effects of MMP-1 and MMP-7-sparing inhibition (sMMPi) on regional and global LV remodeling when instituted before or after MI. Methods and Results—Pigs instrumented with coronary snares and radiopaque markers within the area at risk were randomized to MI only (n=11) or sMMPi (PGE-530742, 10 mg/kg PO TID) begun 3 days before MI (n=11) or 3 days after MI (n=10). Eleven weight-matched noninstrumented pigs served as reference controls. At 10 days after MI, infarct size was similar between groups (47±3% of the area at risk). Marker area increased from baseline in the MI-only group (10±3%, P <0.05) but was unchanged with sMMPi. LV end-diastolic volume increased in the MI-only group (82±3 mL) compared with controls (56±3 mL, P <0.05) but was attenuated with pre-MI and post-MI sMMPi (69±3 and 69±4 mL, respectively, P <0.05). Collagen content increased in the infarct zone of the MI-only group (34±5%) compared with control (2±1%, P <0.05) but was reduced with pre-MI and post-MI sMMPi (24±1% and 23±2%, P <0.05). Collagen content increased in the border zone (12±2%) and decreased in the remote zone (3±1%) of the pre-MI sMMPi group compared with post-MI sMMPi values (7±1% and 5±1%, P <0.05). Conclusions—Inhibition of MMP-1 and −7 is not required to favorably influence LV remodeling after MI. Moreover, a temporal difference exists with respect to the timing of sMMPi and regional and global myocardial remodeling patterns after MI.

Myocardial matrix metalloproteinase activity and abundance with congestive heart failure

The left ventricular (LV) myocardial collagen matrix has been proposed to participate in the maintenance of LV geometry. Thus alterations in the composition of the LV myocardial collagen matrix may influence LV function. The matrix metalloproteinases (MMPs) are a family of enzymes that contribute to extracellular remodeling in several disease states. However, the types of MMPs expressed in the normal and congestive heart failure (CHF) state and the relation to MMP activity remained unclear. Accordingly, after 3 wk of pacing (240 beats/min), changes in LV function, substrate-specific MMP activity, and MMP subclass abundance were measured in comparison with control pigs (n = 6). Changes in LV function and geometry were measured by echocardiography; LV end-diastolic dimension increased (3.6 +/- 0.1 vs. 6.0 +/- 0.1 cm, P < 0.05) and LV fractional shortening decreased (47 +/- 1 vs. 15 +/- 1%, P < 0.05) compared with controls. Degradation of fibrillar collagen is achieved through the combined action of interstitial collagenase (MMP-1), gelatinase A (MMP-2), and stromelysin (MMP-3) (He, C., S. Wilheilm, A. Pentland, B. Marmer, G. Grant, A. Eisen, and G. Goldberg. Proc. Natl. Acad. Sci. USA 86:2632-2636, 1989; Woessner, J. FASEB J. 5: 2145-2154, 1991). Accordingly, the relative abundance of specific MMPs (MMP-1, MMP-2, and MMP-3) was examined by immunoblotting. With pacing CHF, the relative abundance for MMP-1 increased to 319 +/- 94%, MMP-2 increased to 194 +/- 31%, and MMP-3 increased to 493 +/- 159% (all P < 0.05). With pacing CHF, LV myocardial zymographic activity for the substrate gelatin increased by 119% (P < 0.05) and for the substrate collagen III by 153% (P < 0.05) over controls. Caseinolytic activity also increased with pacing CHF by 139% (P < 0.05) over controls. In conclusion, LV myocardial MMP activity and abundance increased with pacing-induced CHF. These findings demonstrate that pacing-induced CHF leads to changes in myocardial MMP activity and expression that may be responsible for LV remodeling in CHF.The left ventricular (LV) myocardial collagen matrix has been proposed to participate in the maintenance of LV geometry. Thus alterations in the composition of the LV myocardial collagen matrix may influence LV function. The matrix metalloproteinases (MMPs) are a family of enzymes that contribute to extracellular remodeling in several disease states. However, the types of MMPs expressed in the normal and congestive heart failure (CHF) state and the relation to MMP activity remained unclear. Accordingly, after 3 wk of pacing (240 beats/min), changes in LV function, substrate-specific MMP activity, and MMP subclass abundance were measured in comparison with control pigs ( n = 6). Changes in LV function and geometry were measured by echocardiography; LV end-diastolic dimension increased (3.6 ± 0.1 vs. 6.0 ± 0.1 cm, P < 0.05) and LV fractional shortening decreased (47 ± 1 vs. 15 ± 1%, P < 0.05) compared with controls. Degradation of fibrillar collagen is achieved through the combined action of interstitial collagenase (MMP-1), gelatinase A (MMP-2), and stromelysin (MMP-3) (He, C., S. Wilheilm, A. Pentland, B. Marmer, G. Grant, A. Eisen, and G. Goldberg. Proc. Natl. Acad. Sci. USA 86: 2632-2636, 1989; Woessner, J. FASEB J. 5: 2145-2154, 1991). Accordingly, the relative abundance of specific MMPs (MMP-1, MMP-2, and MMP-3) was examined by immunoblotting. With pacing CHF, the relative abundance for MMP-1 increased to 319 ± 94%, MMP-2 increased to 194 ± 31%, and MMP-3 increased to 493 ± 159% (all P < 0.05). With pacing CHF, LV myocardial zymographic activity for the substrate gelatin increased by 119% ( P < 0.05) and for the substrate collagen III by 153% ( P < 0.05) over controls. Caseinolytic activity also increased with pacing CHF by 139% ( P < 0.05) over controls. In conclusion, LV myocardial MMP activity and abundance increased with pacing-induced CHF. These findings demonstrate that pacing-induced CHF leads to changes in myocardial MMP activity and expression that may be responsible for LV remodeling in CHF.

Cardiac Support Device Modifies Left Ventricular Geometry and Myocardial Structure After Myocardial Infarction

Background—Whether mechanical restraint of the left ventricle (LV) can influence remodeling after myocardial infarction (MI) remains poorly understood. This study surgically placed a cardiac support device (CSD) over the entire LV and examined LV and myocyte geometry and function after MI. Methods and Results—Post-MI sheep (35 to 45 kg; MI size, 23±2%) were randomized to placement of the CorCap CSD (Acorn Cardiovascular, Inc) (MI+CSD; n=6) or remained untreated (MI only; n=5). Uninstrumented sheep (n=10) served as controls. At 3 months after MI, LV end-diastolic volume (by MRI) was increased in the MI only group compared with controls (98±8 versus 43±4 mL; P<0.05). In the MI+CSD group, LV end-diastolic volume was lower than MI only values (56±7 mL; P<0.05) but remained higher than controls (P<0.05). Isolated LV myocyte shortening velocity was reduced by 35% from control values (P<0.05) in both MI groups. LV myocyte &bgr;-adrenergic response was reduced with MI but normalized in the MI+CSD group. LV myocyte length increased in the MI group and was reduced in the MI+CSD group. Relative collagen content was increased and matrix metalloproteinase-9 was decreased within the MI border region of the CSD group. Conclusions—A CSD beneficially modified LV and myocyte remodeling after MI through both cellular and extracellular mechanisms. These findings provide evidence that nonpharmacological strategies can interrupt adverse LV remodeling after MI.

Treatment With a Growth Hormone Secretagogue in a Model of Developing Heart Failure Effects on Ventricular and Myocyte Function

BackgroundExogenous administration of growth hormone (GH) and subsequently increased production of insulin-like growth factor-1 can influence left ventricular (LV) myocardial growth and geometry in the setting of congestive heart failure (CHF). This study determined the effects of an orally active GH secretagogue (GHS) treatment that causes a release of endogenous GH on LV function and myocyte contractility in a model of developing CHF. Methods and ResultsPigs were randomly assigned to the following treatment groups: (1) chronic rapid pacing at 240 bpm for 3 weeks (n=11); (2) chronic rapid pacing and GHS (CP-424,391 at 10 mg·kg−1·d−1, n=9); and (3) sham controls (n=8). In the untreated pacing CHF group, LV fractional shortening was reduced (21±2% versus 47±2%) and peak wall stress increased (364±21 versus 141±5 g/cm2) from normal control values (P <0.05). In the GHS group, LV fractional shortening was higher (29±2%) and LV peak wall stress lower (187±126 g/cm2) than untreated CHF values (P <0.05). With GHS treatment, the ratio of LV mass to body weight increased by 44% from untreated values. Steady-state myocyte velocity of shortening was reduced with pacing CHF compared with controls (38±1 versus 78±1 &mgr;m/s, P <0.05) and was increased from pacing CHF values with GHS treatment (55±7 &mgr;m/s, P <0.05). ConclusionsThe improved LV pump function that occurred with GHS treatment in this model of CHF was most likely a result of favorable effects on LV myocardial remodeling and contractile processes. On the basis of these results, further studies are warranted to determine the potential role of GH secretagogues in the treatment of CHF.

Angiotensin converting enzyme inhibition, AT1 receptor inhibition, and combination therapy with pacing induced heart failure : effects on left ventricular performance and regional blood flow patterns

BACKGROUND AT1 receptor activation has been demonstrated to cause increased vascular resistance properties which may be of particular importance in the setting of congestive heart failure (CHF). The overall goal of this study was to examine the effects of ACE inhibition (ACEI) alone, AT1 receptor blockade alone and combined ACEI and AT1 receptor blockade on LV pump function, systemic hemodynamics and regional blood flow patterns in the normal state and with the development of pacing induced CHF, both at rest and with treadmill induced exercise. METHODS AND RESULTS Pigs (25 kg) were instrumented in order to measure cardiac output (CO), systemic (SVR) and pulmonary vascular (PVR) resistance, neurohormonal system activity, and myocardial blood flow distribution in the conscious state and assigned to one of 4 groups: (1) rapid atrial pacing (240 bpm) for 3 weeks (n = 7); (2) ACEI (benazeprilat, 3.75 mg/day) and pacing (n = 7); (3) AT1 receptor blockade (valsartan, 60 mg/day) and rapid pacing (n = 7); and (4) ACEI and AT1 receptor blockade (benazeprilat/valsartan, 1/60 mg/day, respectively) and pacing (n = 7). Measurements were obtained at rest and with treadmill exercise (15 degrees, 3 miles/h; 10 min) in the normal control state and after the completion of the treatment protocols. With rapid pacing, CO was reduced at rest and with exercise compared to controls. ACEI or AT1 blockade normalized CO at rest, but remained lower than control values with exercise. Combination therapy normalized CO both at rest and with exercise. Resting SVR in the CHF group was higher than controls and SVR fell to a similar degree with exercise; all treatment groups reduced resting SVR. With exercise, SVR was reduced from rapid pacing values in the ACEI and combination therapy groups. PVR increased by over 4-fold in the rapid pacing group both at rest and with exercise, and was reduced in all treatment groups. In the combination therapy group, PVR was similar to control values with exercise. Plasma catecholamines and endothelin levels were increased by over 3-fold with chronic rapid pacing, and were reduced in all treatment groups. In the combination therapy group, the relative increase in catecholamines and endothelin with exercise were significantly blunted when compared to rapid pacing only values. LV myocardial blood flow at rest was reduced in the rapid pacing only and monotherapy groups, but was normalized with combination therapy. CONCLUSION These findings suggest that with developing CHF, combined ACE inhibition and AT1 receptor blockade improved vascular resistive properties and regional blood flow distribution to a greater degree than that of either treatment alone. Thus, combined ACEI and AT1 receptor blockade may provide unique benefits in the setting of CHF.

Chronic Matrix Metalloproteinase Inhibition Following Myocardial Infarction in Mice: Differential Effects on Short and Long-Term Survival

Left ventricular (LV) remodeling occurs after myocardial infarction (MI), and the matrix metalloproteinases (MMPs) contribute to adverse LV remodeling after MI. Short-term pharmacological MMP inhibition (MMPi; days to weeks) in animal models of MI have demonstrated a reduction in adverse LV remodeling. However, the long-term effects (months) of MMPi on survival and LV remodeling after MI have not been examined. MI was induced in adult mice (n = 131) and, at 3 days post-MI, assigned to MMPi [MI-MMPi: (s)-2-(4-bromo-biphenyl-4-sulfonylamino)-3-methyl-butyric acid (PD200126), 7.5 mg/day/p.o., n = 64] or untreated (MI-only, n = 67). Unoperated mice (n = 16) served as controls. The median survival in the MI-only group was 5 days, whereas median survival was significantly greater in the MI-MMPi group at 38 days (p < 0.05). However, with prolonged MMPi (>120 days), a significant divergence in the survival curves occurred in which significantly greater mortality was observed with prolonged MMPi (p < 0.05). LV echocardiography at 6 months revealed LV dilation in the MI-only and MI-MMPi groups (154 ± 14 and 219 ± 24 μl) compared with control (67 ± 4 μl, p < 0.05), with a greater degree of dilation in the MI-MMPi group (p < 0.05). MMPi conferred a beneficial effect on survival early post-MI, but prolonged MMPi (>3 months) was associated with higher mortality and adverse LV remodeling. These unique results suggest that an optimal temporal window exists with respect to pharmacological interruption of MMP activity in the post-MI period.

Effects of Combined Angiotensin II and Endothelin Receptor Blockade With Developing Heart Failure Effects on Left Ventricular Performance

BackgroundThe goal of this study was to determine the comparative effects of angiotensin II type 1 (AT1) receptor inhibition alone, endothelin-1 (ET) receptor blockade alone, and combined receptor blockade on left ventricular (LV) function, contractility, and neurohormonal system activity in a model of congestive heart failure (CHF). Methods and ResultsPigs were randomly assigned to each of 5 groups: (1) rapid atrial pacing (240 bpm) for 3 weeks (n=9), (2) concomitant AT1 receptor blockade (valsartan, 3 mg/kg per day) and rapid pacing (n=8), (3) concomitant ET receptor blockade (bosentan, 50 mg/kg BID) and rapid pacing (n=8), (4) concomitant combined AT1 and ET receptor inhibition and rapid pacing (n=8), and (5) sham-operated control (n=9). LV stroke volume was reduced from the control value after rapid pacing, was unchanged with either AT1 or ET receptor blockade alone, but was improved with combination treatment. LV peak wall stress was reduced in both groups with ET receptor blockade compared with the rapid pacing group. Plasma norepinephrine levels were increased by >3-fold after rapid pacing, remained increased in the monotherapy groups, but were reduced after combination treatment. LV myocyte velocity of shortening was reduced after rapid pacing–induced CHF, remained reduced after AT1 receptor blockade, increased after ET receptor blockade (compared with rapid pacing–induced CHF values), and returned to within control values after combined blockade. ConclusionsCombined AT1 and the ET receptor blockade in this model of CHF improved LV pump function, and contributory factors included the effects of LV loading conditions, neurohormonal system activity, and myocardial contractile performance. Thus, combined receptor blockade may provide a useful combinatorial therapeutic approach in CHF.

Cardiorenal effects of adenosine subtype 1 (A1) receptor inhibition in an experimental model of heart failure

BACKGROUND Elaboration of a number of bioactive substances, including adenosine, occurs in heart failure (HF). Adenosine, through the adenosine subtype 1 (A1) receptor, can reduce renal perfusion pressure and glomerular filtration rate and increase tubular sodium reabsorption, which can affect natriuresis and aquaresis. Accordingly, the present study examined the acute effects of selective A1 receptor blockade on hemodynamics and renal function in a model of HF. STUDY DESIGN HF was induced in adult pigs (n = 19) by chronic pacing (240 beats/min for 3 weeks). The pigs were then instrumented for hemodynamic and renal function measurements. After baseline measurements were taken, pigs received either A1 block [ 1 mg/kg BG9719 (1,3-dipropyl-8-[2(5,6-epoxynorbornyl)]xanthine; n = 9)] or infusion of vehicle (n = 10), and measurements were repeated at intervals for up to 2 hours. Normal controls (n = 7) were included for comparison. RESULTS Cardiac output remained unchanged between the A1 block and vehicle groups throughout the study. Pulmonary vascular resistance fell 38% from baseline at 10 minutes post-A1 block in the HF group (p < 0.05) with no change in the vehicle group. At 10 minutes post-A1 block, urine flow increased sixfold and sodium excretion increased over 10-fold (for both, p < 0.05) with no change in the vehicle group. At 10 minutes post-A1 block, creatinine clearance increased with no change in the vehicle group. At 10 minutes post-A1 block, plasma renin activity had increased over threefold (p <0.05), and it returned to baseline levels by 30 minutes post-A1 block. CONCLUSIONS The unique findings from this study were threefold. First, increased A1 receptor activation contributes to renal mediated fluid retention in HF. Second, selective A1 blockade can induce diuresis without hemodynamic compromise and with possible benefit to pulmonary resistance in a model of HF. A1 blockade transiently increased plasma renin activity with no change in hemodynamics. These unique results suggest that selective A1 blockade can be a useful adjunctive diuretic in the setting of HF.

Selective targeting of matrix metalloproteinase inhibition in post-infarction myocardial remodeling.

Background: A cause-effect relationship has been established between MMP activation and left ventricular (LV) remodeling following myocardial infarction. The goal of the present study was to examine a selective MMP inhibitor (sMMPi) strategy that effectively spared MMP-1, -3, and -7 with effect to regional and global left ventricular remodeling in a pig model of myocardial infarction. Methods and Results: Pigs instrumented with coronary snares and radiopaque markers within the area at risk were randomized to myocardial infarction-only (n = 10) or sMMPi (PGE-530742, 1 mg/kg TID) begun 3 days prior to myocardial infarction. Ten weight-matched noninstrumented pigs served as reference controls. Left ventricular end-diastolic volume in the myocardial infarction-only group was increased from baseline (81 ± 3 mL versus 55 ± 4 mL, respectively, P < 0.05) but was attenuated with sMMPi (67 ± 3 mL, P < 0.05). Fractional area of shortening of marker area was decreased in the myocardial infarction-only group (change from baseline −63 ± 10%, P < 0.05) but this effect was attenuated with sMMPi (−28 ± 14%, P < 0.05), indicative of less dyskinesis of the infarct region with sMMPi. Wall stress was reduced within both the septal and posterior wall regions with sMMPi. Myocardial MMP-2 activity was decreased in both remote and border areas of sMMPi-treated samples compared with myocardial infarction-only values, consistent with pharmacologic MMP inhibition. Conclusions: Selective MMP inhibition favorably affected regional myocardial geometry and decreased left ventricular dilation post-myocardial infarction. This study suggests that a strategy of selective MMP inhibition of a limited array of MMPs may be an achievable goal in preventing pathologic left ventricular remodeling post-myocardial infarction.

Modulation of calcium transport improves myocardial contractility and enzyme profiles after prolonged ischemia-reperfusion

BACKGROUND Ischemia-reperfusion (IR) injury causes myocardial dysfunction in part through intracellular calcium overload. A recently described pharmacologic compound, MCC-135 (5-methyl-2-[1-piperazinyl] benzenesulfonic acid monohydrate, Mitsubishi Pharma Corporation), alters intracellular calcium levels. This project tested the hypothesis that MCC-135 would influence regional myocardial contractility when administered at reperfusion and after a prolonged period of ischemia. METHODS A circumflex snare and sonomicrometry crystals within remote and area-at-risk regions were placed in pigs (n = 18, 32 kg). Coronary occlusion was instituted for 120 minutes followed by 180 minutes of reperfusion. At 105 minutes of ischemia pigs were randomly assigned to IR only (n = 11) or MCC-135 (IR-MCC [300 microg. kg(-1). h(-1), n = 7]) administered intravenously. Regional myocardial contractility was determined by calculation of the regional end-systolic pressure-dimension relation (RESPDR [mm Hg/cm]). Myocardial injury was determined by measurement of plasma levels of myocyte-specific enzymes. RESULTS At 90 minutes ischemia, mean troponin-I was 35 +/- 8 ng/mL with no significant difference between groups. At 180 minutes reperfusion, heart rate was increased by 18% +/- 5% in the IR only group (p < 0.05) and was reduced by 11% +/- 4% with IR-MCC (p < 0.05). At 90 minutes ischemia RESPDR was reduced from baseline by 51% +/- 6% (p < 0.05). By 30 minutes reperfusion, reductions in RESPDR were attenuated with IR-MCC compared with IR only values. The CK-MB levels were increased at 180 minutes reperfusion in the IR only group (52 +/- 9 ng/mL) compared with baseline (6 +/- 1 ng/mL, p < 0.05) but were attenuated with IR-MCC (24 +/- 4 ng/mL, p < 0.05) compared with IR only values. CONCLUSIONS Despite similar degrees of injury at 90 minutes ischemia MCC-135 improved regional contractility and reduced the egress of CK-MB. Moreover MCC-135 was associated with decreased heart rate, a determinant of myocardial oxygen demand. Pharmacologic modulation of calcium transport ameliorates myocardial dysfunction in the acute IR period.