Overlapping roles of NADPH oxidase 4 for diabetic and gadolinium-based contrast agent-induced systemic fibrosis.

Dozens of millions of people are exposed to gadolinium-based contrast agents annually for enhanced magnetic resonance imaging. Gadolinium-based contrast agents are known nephrotoxins and can trigger the potentially fatal condition of systemic fibrosis. Risk factors are practically entirely undefined. We examined the role of NADPH oxidase 4 (Nox4) in gadolinium-induced systemic disease. Age- and weight-matched mice were randomized to experimental diabetes (streptozotocin) and control groups followed by systemic gadolinium-based contrast agent treatment. Nox4-deficient mice were randomized to experimental diabetes and gadolinium-based contrast agent treatment. Skin fibrosis and cellular infiltration were apparent in both gadolinium-based contrast agent-treated and experimental diabetes groups. Similarly, both groups demonstrated renal pathologies with evidence of reactive oxygen species generation. Deletion of Nox4 abrogated both skin and renal pathology, whether from diabetes or gadolinium-based contrast agent treatment. These discoveries demonstrate the importance of Nox4 in gadolinium-based contrast agent- and diabetes-induced fibrosis.NEW & NOTEWORTHY A mouse model of gadolinium-based contrast agent- and diabetes-induced fibrosis was used to demonstrate the role of NADPH oxidase 4 (Nox4) in gadolinium-induced systemic disease. Using these models, we established the role of Nox4 as a mediator of reactive oxygen species generation and subsequent skin and kidney fibrosis. These novel findings have defined Nox-4-mediated mechanisms by which gadolinium-based contrast agents induce systemic diseases.

The safety of magnetic resonance imaging contrast agents.

Gadolinium-based contrast agents are increasingly used in clinical practice. While these pharmaceuticals are verified causal agents in nephrogenic systemic fibrosis, there is a growing body of literature supporting their role as causal agents in symptoms associated with gadolinium exposure after intravenous use and encephalopathy following intrathecal administration. Gadolinium-based contrast agents are multidentate organic ligands that strongly bind the metal ion to reduce the toxicity of the metal. The notion that cationic gadolinium dissociates from these chelates and causes the disease is prevalent among patients and providers. We hypothesize that non-ligand-bound (soluble) gadolinium will be exceedingly low in patients. Soluble, ionic gadolinium is not likely to be the initial step in mediating any disease. The Kidney Institute of New Mexico was the first to identify gadolinium-rich nanoparticles in skin and kidney tissues from magnetic resonance imaging contrast agents in rodents. In 2023, they found similar nanoparticles in the kidney cells of humans with normal renal function, likely from contrast agents. We suspect these nanoparticles are the mediators of chronic toxicity from magnetic resonance imaging contrast agents. This article explores associations between gadolinium contrast and adverse health outcomes supported by clinical reports and rodent models.

The onset of rare earth metallosis begins with renal gadolinium-rich nanoparticles from magnetic resonance imaging contrast agent exposure.

The leitmotifs of magnetic resonance imaging (MRI) contrast agent-induced complications range from acute kidney injury, symptoms associated with gadolinium exposure (SAGE)/gadolinium deposition disease, potentially fatal gadolinium encephalopathy, and irreversible systemic fibrosis. Gadolinium is the active ingredient of these contrast agents, a non-physiologic lanthanide metal. The mechanisms of MRI contrast agent-induced diseases are unknown. Mice were treated with a MRI contrast agent. Human kidney tissues from contrast-naïve and MRI contrast agent-treated patients were obtained and analyzed. Kidneys (human and mouse) were assessed with transmission electron microscopy and scanning transmission electron microscopy with X-ray energy-dispersive spectroscopy. MRI contrast agent treatment resulted in unilamellar vesicles and mitochondriopathy in renal epithelium. Electron-dense intracellular precipitates and the outer rim of lipid droplets were rich in gadolinium and phosphorus. We conclude that MRI contrast agents are not physiologically inert. The long-term safety of these synthetic metal-ligand complexes, especially with repeated use, should be studied further.

Gadolinium Deposition Disease: A Case Report and the Prevalence of Enhanced MRI Procedures Within the Veterans Health Administration.

Background: Gadolinium (Gd) usage in the Veterans Health Administration is increasing and patients with renal disease are frequently exposed. Gd is not entirely eliminated within 24 hours after administration, which may pose long-term adverse effects. Case Presentation: A Vietnam-era veteran aged > 70 years presented for evaluation of Gd-based contrast agent-induced chronic multisymptom illness. In the course of his routine clinical care, he was exposed to repeated Gd-enhanced magnetic resonance imaging studies. After his second Gd-based contrast agent exposure, he noted rash, pain, headaches, and hoarseness. Years after the exposure to the contrast agents, he continued to have detectable Gd in urine and serum. Conclusions: Practitioners should be aware of long-term intracellular Gd retention (including the brain) as patients increasingly turn to consultants with concerns about Gd deposition disease. Data from patient advocates demonstrate that Gd is eliminated in intermediate and long phases, which may represent a multicompartment model. The commercialization of Gd use in imaging studies is outpacing the science addressing the long-term consequences of harboring this alien, toxic, nonphysiologic rare earth metal.

Dysnatremia in Gastrointestinal Disorders.

The primary solute of the milieu intérieur is sodium and accompanying anions. The solvent is water. The kidneys acutely regulate homeostasis in filtration, secretion, and resorption of electrolytes, non-electrolytes, and minerals while balancing water retention and clearance. The gastrointestinal absorptive and secretory functions enable food digestion and water absorption needed to sustain life. Gastrointestinal perturbations including vomiting and diarrhea can lead to significant volume and electrolyte losses, overwhelming the renal homeostatic compensatory mechanisms. Dysnatremia, potassium and acid-base disturbances can result from gastrointestinal pathophysiologic processes. Understanding the renal and gastrointestinal contributions to homeostatis are important for the clinical evaluation of perturbed volume disturbances.

CC chemokine receptor 5 deletion impairs macrophage activation and induces adverse remodeling following myocardial infarction.

Post-myocardial infarction (MI), chemokine homing of inflammatory cells into the injured left ventricle (LV) regulates ventricular remodeling, in part by stimulating the extracellular matrix response. The CC chemokine receptor 5 (CCR5) is a key chemokine receptor expressed on macrophages, and CCR5 ligands are highly upregulated post-MI. We hypothesized that deletion of CCR5 would attenuate adverse remodeling by decreasing inflammatory cell recruitment. Accordingly, we examined LV function, macrophage recruitment and activation, and collagen content in wild-type (WT, n = 25) and CCR5 null (n = 33) mice at 7 days post-MI. Both groups had similar infarct sizes (44 ± 2% in WT and 42 ± 2% in CCR5 null; P = 0.37). However, the LV remodeling index (end diastolic volume/LV mass) increased to a larger extent in CCR5 null (1.28 ± 0.08 µl/mg for CCR5 null and 1.02 ± 0.06 µl/mg for WT; P < 0.05). Although numbers of infiltrated macrophages were similar in WT and CCR5 null mice, CCR5-deficient macrophages isolated from the infarct zone displayed >50% decrease in gene expression levels of proinflammatory activation markers (interleukin-1ß, interleukin-6, and tumor necrosis factor-α), as well as anti-inflammatory activation markers (arginase 1, CD163, mannose receptor, and transforming growth factor-ß1) compared with WT (all P < 0.05). Concomitant with the reduced macrophage activation, heat shock protein-47 and collagen type I precursor levels in the infarct region decreased in the CCR5 null (1.2 ± 0.3 units in the CCR5 null and 2.3 ± 0.4 units in the WT; P < 0.05), while collagen fragments increased (88.3 ± 5.9 units in the CCR5 null and 32.7 ± 8.5 units in the WT; P < 0.05). We conclude that CCR5 deletion impairs LV remodeling by hindering macrophage activation, which stimulates an imbalance in collagen metabolism and increases the remodeling index.

Rosuvastatin-Induced Rhabdomyolysis, Pancreatitis, Transaminitis, and Acute Kidney Injury.

Changing medications within a drug class requires considering the indication and dosage, possible adverse effects, and drug-drug interactions.

Caspase inhibition modulates left ventricular remodeling following myocardial infarction through cellular and extracellular mechanisms.

BACKGROUND: Myocyte death occurs by necrosis and caspase-mediated apoptosis in myocardial infarction (MI). In vitro studies suggest caspase activation causes myocardial contractile protein degradation without inducing apoptosis. Thus, caspase activation may evoke left ventricular (LV) remodeling through independent processes post-MI. The effects of caspase activation on LV geometry post-MI remain unclear. This project applied pharmacologic caspase inhibition (CASPI) to a porcine model of MI. METHODS AND RESULTS: Pigs (34 kg) were instrumented to induce 60 minutes of coronary artery occlusion followed by reperfusion and a 7-day follow-up period. Upon reperfusion, the pigs were randomized to saline (n = 12) or CASPI (n = 10, IDN6734, 6 mg/kg i.v., then 6 mg/kg/h for 24 hours). Plasma troponin-I values were reduced with CASPI compared with saline at 24 hours post-MI (133 +/- 15 vs. 189 +/- 20 ng/mL, respectively, P < 0.05). LV end-diastolic area (echocardiography) and interregional length (sonomicrometry) increased from baseline in both groups but were attenuated with CASPI by 40% and 90%, respectively (P < 0.05). Myocyte length was reduced with CASPI compared with saline (128 +/- 3 vs. 141 +/- 4 microm, respectively, P < 0.05). Plasma-free pro-matrix metalloproteinase-2 values increased from baseline with CASPI (27% +/- 6%, P < 0.05) indicative of reduced conversion to active MMP-2. Separate in vitro studies demonstrated that activated caspase species cleaved pro-MMP-2 yielding active MMP-2 forms and that MMP activity was increased in the presence of activated caspase-3. CONCLUSIONS: CASPI attenuated regional and global LV remodeling post-MI and altered viable myocyte geometry. Caspases increased MMP activity in vitro, whereas CASPI modified conversion of MMP-2 to the active form in vivo. Taken together, the results of the present study suggest that the elaboration of caspases post-MI likely contribute to LV remodeling through both cellular and extracellular mechanisms.

Gadolinium-Based Contrast Agent Use, Their Safety, and Practice Evolution.

Gadolinium-based contrast agents (GBCAs) have provided much needed image enhancement in magnetic resonance imaging (MRI) important in the advancement of disease diagnosis and treatment. The paramagnetic properties of ionized gadolinium have facilitated these advancements, but ionized gadolinium carries toxicity risk. GBCAs were formulated with organic chelates designed to reduce these toxicity risks from unbound gadolinium ions. They were preferred over iodinated contrast used in computed tomography and considered safe for use. As their use expanded, the development of new diseases associated with their use (including nephrogenic systemic fibrosis) has drawn more attention and ultimately caution with their clinical administration in those with impaired renal function. Use of GBCAs in those with preserved renal function was considered to be safe. However, in this new era with emerging clinical and experimental evidence of brain gadolinium deposition in those with repeated exposure, these safety assumptions are once again brought into question. This review article aims to add new perspectives in thinking about the role of GBCA in current clinical use. The new information begs for further discussion and consideration of the risk-benefit ratio of use of GBCAs.

Biomechanical Restoration Potential of Pentagalloyl Glucose after Arterial Extracellular Matrix Degeneration.

The objective of this study was to quantify pentagalloyl glucose (PGG) mediated biomechanical restoration of degenerated extracellular matrix (ECM). Planar biaxial tensile testing was performed for native (N), enzyme-treated (collagenase and elastase) (E), and PGG (P) treated porcine abdominal aorta specimens (n = 6 per group). An Ogden material model was fitted to the stress-strain data and finite element computational analyses of simulated native aorta and aneurysmal abdominal aorta were performed. The maximum tensile stress of the N group was higher than that in both E and P groups for both circumferential (43.78 ± 14.18 kPa vs. 10.03 ± 2.68 kPa vs. 13.85 ± 3.02 kPa; p = 0.0226) and longitudinal directions (33.89 ± 8.98 kPa vs. 9.04 ± 2.68 kPa vs. 14.69 ± 5.88 kPa; p = 0.0441). Tensile moduli in the circumferential direction was found to be in descending order as N > P > E (195.6 ± 58.72 kPa > 81.8 ± 22.76 kPa > 46.51 ± 15.04 kPa; p = 0.0314), whereas no significant differences were found in the longitudinal direction (p = 0.1607). PGG binds to the hydrophobic core of arterial tissues and the crosslinking of ECM fibers is one of the possible explanations for the recovery of biomechanical properties observed in this study. PGG is a beneficial polyphenol that can be potentially translated to clinical practice for preventing rupture of the aneurysmal arterial wall.

Matrix metalloproteinase-7 affects connexin-43 levels, electrical conduction, and survival after myocardial infarction.

BACKGROUND: Matrix metalloproteinases (MMPs) contribute to left ventricular remodeling after myocardial infarction (MI). Specific causative roles of particular MMPs, however, remain unclear. MMP-7 is abundant in cardiomyocytes and macrophages, but MMP-7 function after MI has not been defined. METHODS AND RESULTS: Wild-type (WT; n=55) and MMP-7-null (MMP-7-/-; n=32) mice underwent permanent coronary artery ligation for 7 days. MI sizes were similar, but survival was greatly improved in MMP-7-/- mice. The survival difference could not be attributed to differences in left ventricular dilation because end-diastolic volumes increased similarly. ECG analysis revealed a prolonged PR interval in WT but not in MMP-7-/- post-MI mice. Post-MI conduction velocity, determined by optically mapping electrical wavefront propagation, decreased to 78+/-6% of control for WT and was normalized in MMP-7-/- mice. In WT mice, slower conduction velocity correlated with a 53% reduction in the gap junction protein connexin-43. Direct binding of MMP-7 to connexin-43, determined by surface plasmon resonance technology, occurred in a dose-dependent manner. Connexin-43 processing by MMP-7 was confirmed by in silico and in vitro substrate analyses and MMP-7 infusion induced arrhythmias in vivo. CONCLUSIONS: MMP-7 deletion results in improved survival and myocardial conduction patterns after MI. This is the first report to implicate MMP-7 in post-MI remodeling and to demonstrate that connexin-43 is a novel MMP-7 substrate.

Age-dependent changes in myocardial matrix metalloproteinase/tissue inhibitor of metalloproteinase profiles and fibroblast function.

OBJECTIVE: To evaluate the effects of aging on left ventricular (LV) geometry, collagen levels, matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) abundance, and myocardial fibroblast function. METHODS: Young (3-month-old; n=28), middle-aged (MA; 15-month-old; n=17), and old (23-month-old; n=16) CB6F1 mice of both sexes were used in this study. Echocardiographic parameters were measured; collagen, MMP, and TIMP levels were determined for both the soluble and insoluble protein fractions; and fibroblast function was evaluated. RESULTS: LV end-diastolic dimensions and wall thickness increased in both MA and old mice, accompanied by increased soluble protein and decreased insoluble collagen. Immunoblotting revealed differential MMP/TIMP profiles. Compared to MA levels, MMP-3, MMP-8, MMP-9, MMP-12, and MMP-14 increased, and TIMP-3 and TIMP-4 decreased in the insoluble fraction of old mice, suggesting increased extracellular matrix (ECM) degradative capacity. Fibroblast proliferation was blunted with age. CONCLUSION: This study, for the first time, identified specific differences in cellular and extracellular processes that likely contribute to age-dependent ECM remodeling.

Myocardial infarct expansion and matrix metalloproteinase inhibition.

BACKGROUND: A potential mechanism for left ventricular (LV) remodeling after myocardial infarction (MI) is activation of the matrix metalloproteinases (MMPs). This study examined the effects of MMP inhibition (MMPi) on regional LV geometry and MMP levels after MI. METHODS AND RESULTS: In pigs instrumented with radiopaque markers to measure regional myocardial geometry, MI was created by ligating the obtuse marginals of the circumflex artery. In the first study, pigs were randomized to MMPi (n=7; PD166793, 20 mg x kg(-1) x d(-1)) or MI only (n=7) at 5 days after MI, and measurements were performed at 2 weeks. Regional MI areas were equivalent at randomization and were increased in the MI-only group at 2 weeks after MI compared with the MMPi group. In the second study, pigs randomized to MMPi (n=9) or MI only (n=8) were serially followed up for 8 weeks. At 8 weeks after MI, LV end-diastolic dimension was lower with MMPi than in the MI-only group (4.7+/-0.1 versus 5.1+/-0.1 cm, P<0.05). Regional MI area was reduced with MMPi at 8 weeks after MI (1.3+/-0.1 versus 1.7+/-0.1 cm2, P<0.05). MMPi reduced ex vivo MMP proteolytic activity. In the MI region, membrane-type MMP levels were normalized and levels of the endogenous tissue inhibitor of MMPs (TIMP-1) were increased compared with normal levels with MMPi. These effects were not observed in the MI-only group. CONCLUSIONS: MMPi attenuated the degree of post-MI LV dilation and expansion of the infarct during the late phase of MI healing. In addition, exogenous MMPi caused region-specific modulation of certain MMP and TIMP species.

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.

Direct inhibition of the sodium/hydrogen exchanger after prolonged regional ischemia improves contractility on reperfusion independent of myocardial viability.

BACKGROUND: A mechanism for myocardial dysfunction after ischemia and reperfusion is Na(+)/H(+) exchanger activation. Although past in vivo models of limited ischemia and reperfusion intervals demonstrate that Na(+)/H(+) exchanger inhibition confers myocardial protection when administered at the onset of ischemia, the effect of Na(+)/H(+) exchanger inhibition on myocardial function after prolonged ischemia and reperfusion remains unknown. This investigation tested the hypothesis that Na(+)/H(+) exchanger inhibition instituted at reperfusion and after prolonged coronary occlusion in pigs would influence myocardial contractility independent of myocardial viability. METHODS: A coronary snare and sonomicrometry crystals were placed in pigs (n = 21, 32 kg). Coronary occlusion was instituted for 120 minutes followed by reperfusion for 180 minutes. At 105 minutes of ischemia, pigs were randomized to ischemia and reperfusion only (saline solution, n = 11) or Na(+)/H(+) exchanger inhibition (HOE-642, 3 mg/kg intravenously, n = 10). Myocardial injury was determined by tissue staining and measurement of plasma myocyte-specific enzymes. Myocardial contractility was determined by calculation of the regional end-systolic pressure-dimension relation (millimeters of mercury per centimeter) and by assessment of interregional shortening. RESULTS: Infarct size was not different between groups (39% +/- 6%, P =.26). Moreover, at 180 minutes of reperfusion, plasma troponin-I and creatine kinase MB values had increased to identical levels in the ischemia and reperfusion-only and Na(+)/H(+) exchanger inhibition groups (300 +/- 35 and 50 +/- 6 ng/mL, respectively). At 90 minutes of ischemia, regional end-systolic pressure-dimension relation decreased from baseline (5.7 +/- 0.5 versus 2.7 +/- 0.3, P <.05) in the area at risk. By 30 minutes of reperfusion, regional end-systolic pressure-dimension relation decreased further in the ischemia and reperfusion-only group (1.6 +/- 0.2, P <.05), but improved with Na(+)/H(+) exchanger inhibition (4.4 +/- 0.7, P <.05). CONCLUSIONS: Na(+)/H(+) exchanger inhibition instituted at reperfusion improved contractility independent of myocardial viability as assessed by absolute infarct size and myocyte-specific enzyme release. Thus, modulation of Na(+)/H(+) exchanger activity in the setting of prolonged ischemia and reperfusion may hold therapeutic potential.

Matrix metalloproteinase inhibition modifies left ventricular remodeling after myocardial infarction in pigs.

BACKGROUND: Global and regional shape changes that occur within the left ventricular wall after myocardial infarction have been termed infarct expansion. A potential mechanism for this postinfarction remodeling is activation of the matrix metalloproteinases. Accordingly, the present study examined the effects of matrix metalloproteinase inhibition on left ventricular global geometry after myocardial infarction in pigs. METHODS: Myocardial infarction was created in pigs by means of occlusion of the first and second obtuse marginal branches of the circumflex coronary artery, resulting in a uniform left ventricular free wall infarct size of 21% +/- 2%. At 5 days after infarction, the pigs were randomized to undergo broad-spectrum matrix metalloproteinase inhibition (n = 9; PD166793, 20 mg. kg(-1). d(-1) by mouth) or myocardial infarction alone (n = 8). Ten pigs served as noninfarction control animals. Left ventricular end-diastolic area, determined by means of echocardiography, was measured 8 weeks after infarction. RESULTS: Left ventricular end-diastolic area increased in both the myocardial infarction plus broad-spectrum matrix metalloproteinase inhibition and myocardial infarction only groups compared to reference control animals (3.7 +/- 0.2 cm(2)), but was reduced with broad-spectrum matrix metalloproteinase inhibition compared to myocardial infarction alone (4.5 +/- 0.2 vs 4.9 +/- 0.2 cm(2), respectively; P <.05). Regional radial stress within the infarct region increased in both infarction groups when compared to values obtained from reference control animals (599 +/- 152 g/cm(2)), but was attenuated in the myocardial infarction plus broad-spectrum matrix metalloproteinase inhibition group compared to the myocardial infarction alone group (663 +/- 108 vs 1242 +/- 251 g/cm(2), respectively; P <.05). Similarly, regional myocardial stiffness increased in both the myocardial infarction plus broad-spectrum matrix metalloproteinase inhibition and the myocardial infarction only groups compared with that observed in reference control animals (14 +/- 1 rkm, P <.05) but was lower with broad-spectrum matrix metalloproteinase inhibition than with myocardial infarction alone (42 +/- 6 vs 68 +/- 10 rkm, respectively; P <.05). CONCLUSIONS: Matrix metalloproteinase inhibition reduced postinfarction left ventricular dilation, reduced regional myocardial wall stress, and modified myocardial material properties. These unique findings suggest that increased myocardial matrix metalloproteinase activation after infarction contributes directly to the left ventricular remodeling process.

Pharmacologic inhibition of intracellular caspases after myocardial infarction attenuates left ventricular remodeling: a potentially novel pathway.

OBJECTIVE: Myocyte death occurs by necrosis and caspase-mediated apoptosis in the setting of myocardial infarction. In vitro studies suggest that caspase activation within myocytes causes contractile protein degradation without inducing cell death. Thus, caspase activation may evoke left ventricular remodeling through 2 independent processes post-myocardial infarction. However, the effects of caspase activation on left ventricular geometry post-myocardial infarction remain unclear. This project applied broad-spectrum caspase inhibition to a chronic porcine model of myocardial infarction. METHODS: Coronary snares and sonomicrometry crystals in remote and area-at-risk regions were placed in pigs (n = 22, 34 kg). Geometric measurements at end diastole and end systole, including left ventricular area by echocardiography and interregional distance by sonomicrometry, were obtained at baseline. Coronary occlusion was instituted for 60 minutes, followed by reperfusion and repeated geometric measurements at 7 days, including left ventriculography. At reperfusion, pigs were randomized to saline (n = 12) or caspase inhibition (n = 10, IDN6734, 2 mg/kg intravenously, then 2 mg x kg x h for 24 hours) at a dose that achieved desired plasma concentrations (790 +/- 142 ng/mL) as predicted by prior pharmacokinetic studies. RESULTS: Infarct size and 24-hour troponin-I values were not significantly different between the saline and caspase inhibition groups (51% +/- 8% vs 42% +/- 6% and 189 +/- 20 ng/mL vs 152 +/- 26 ng/mL, respectively, P >.10). At 7 days, end-diastole volume was increased in both groups compared with reference control values (47 +/- 1 mL, P <.05), but it was decreased with caspase inhibition (72 +/- 4 mL) compared with saline (84 +/- 4 mL, P <.05). Similarly, end-diastole and end-systole areas increased by 32% +/- 3% and 81% +/- 16% in the saline group but were attenuated with caspase inhibition (19% +/- 3% and 31% +/- 10%, respectively, P <.05). End-diastole interregional distance increased by 30% +/- 7% in the saline group but was attenuated with caspase inhibition (12% +/- 5%, P <.05). CONCLUSION: Despite equivalent degrees of myocardial injury, caspase inhibition reduced post-myocardial infarction left ventricular remodeling as evidenced by multiple, independent assessments of left ventricular dilation. Thus, caspase activation alters left ventricular geometry in the absence of significant effects on myocardial injury.

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.

Development of a total atherosclerotic occlusion with cell-mediated calcium deposits in a rabbit femoral artery using tissue-engineering scaffolds.

This study sought to establish a chronic total occlusion (CTO) model with cell-mediated calcium deposits in rabbit femoral arteries. CTO is the most severe case in atherosclerosis and contains calcium deposits. Previous animal models of CTO do not mimic the gradual occlusion of arteries or have calcium in physiological form. In the present study we tested the strategy of placing tissue-engineering scaffolds preloaded with cells in arteries to develop a novel CTO model. Primary human osteoblasts (HOBs) were first cultured in vitro on polycaprolactone (PCL) scaffolds with 5 ng TGFß1 loading for 28 days for precalcification. The HOB-PCL construct was then implanted into a rabbit femoral artery for an additional 3, 10 or 28 days. At the time of sacrifice, angiograms and gross histology of arteries were captured to examine the occlusion of arteries. Fluorescent staining of calcium and EDS detection of calcium were used to evaluate the presence and distribution of calcium inside arteries. Rabbit femoral arteries were totally occluded over 28 days. Calcium was presented at CTO sites at 3, 10 and 28 days, with the day 10 specimens showing the maximum calcium. Chronic inflammatory response and recanalization were observed in day 28 CTO sites. A novel CTO model with cell-mediated calcium has been successfully established in a rabbit femoral artery. This model can be used to develop new devices and therapies to treat severe atherosclerotic occlusion.

Cardiac-restricted overexpression of membrane type-1 matrix metalloproteinase in mice: effects on myocardial remodeling with aging.

BACKGROUND: The direct consequences of a persistently increased myocardial expression of the unique matrix metalloproteinase (MMP) membrane type-1 (MT1-MMP) on myocardial remodeling remained unexplored. METHODS AND RESULTS: Cardiac-restricted MT1-MMPexp was constructed in mice using the full-length human MT1-MMP gene ligated to the myosin heavy chain promoter, which yielded approximately a 200% increase in MT1-MMP when compared with age/strain-matched wild-type (WT) mice. Left ventricular (LV) function and geometry was assessed by echocardiography in 3-month ("young") WT (n=32) and MT1-MMPexp (n=20) mice and compared with 14-month ("middle-aged") WT (n=58) and MT1-MMPexp (n=35) mice. LV end-diastolic volume was similar between the WT and MT1-MMPexp young groups, as was LV ejection fraction. In the middle-aged WT mice, LV end-diastolic volume and ejection fraction was similar to young WT mice. However, in the MT1-MMPexp middle-aged mice, LV end-diastolic volume was approximately 43% higher and LV ejection fraction 40% lower (both P<0.05). Moreover, in the middle-aged MT1-MMPexp mice, myocardial fibrillar collagen increased by nearly 2-fold and was associated with approximately 3-fold increase in the processing of the profibrotic molecule, latency-associated transforming growth factor binding protein. In a second study, 14-day survival after myocardial infarction was significantly lower in middle-aged MT1-MMPexp mice. CONCLUSIONS: Persistently increased myocardial MT1-MMP expression, in and of itself, caused LV remodeling, myocardial fibrosis, dysfunction, and reduced survival after myocardial injury. These findings suggest that MT1-MMP plays a mechanistic role in adverse remodeling within the myocardium.