Michael O. Griffin

Early Short-Term Treatment With Doxycycline Modulates Postinfarction Left Ventricular Remodeling

Background—Myocardial infarction (MI) is associated with early metalloproteinase (MMP) activation and extracellular matrix (ECM) degradation. We hypothesized that preserving the original ECM of the infarcted left ventricle (LV) by use of early short-term doxycycline (DOX) treatment preserves cardiac structure and function. Methods and Results—LV morphometry and function were measured in 3 groups of rats (sham, MI, and MI+DOX). DOX (30 mg/kg per day) was given orally 48 hours before and 48 hours after MI. Rats were examined at 2 and 4 weeks after MI. By 4 weeks, DOX significantly decreased (P <0.05 versus MI) the heart weight to body weight ratio, myocyte cross-sectional area, and internal LV diameter, whereas it preserved anterior wall thickness within the infarct. Collagen/muscle area fraction did not change in the region of the infarct/scar. Parallel left shifts (versus MI) were observed in pressure-volume relationships of DOX MI rats at all pressures. DOX treatment also shifted passive epicardial strains within the scar area toward normal values. No differences were observed in LV end-diastolic or peak systolic pressures, peak positive or negative LV dP/dt, or isovolumic relaxation rates. Assessment of LV global MMP and MMP-2/9 activities 1 hour after MI using fluorescent probes yielded significant differences with DOX. Conclusions—Brief, early MMP inhibition after MI yields preservation of LV structure and global as well as scar area passive function, supporting the concept that preserving the original ECM early after coronary occlusion lessens ventricular remodeling.

Tetracycline compounds with non-antimicrobial organ protective properties: possible mechanisms of action.

Abstract Tetracyclines were developed as a result of the screening of soil samples for antibiotics. The firstt of these compounds, chlortetracycline, was introduced in 1947. Tetracyclines were found to be highly effective against various pathogens including rickettsiae, as well as both gram-positive and gram-negative bacteria, thus becoming the first class of broad-spectrum antibiotics. Many other interesting properties, unrelated to their antibiotic activity, have been identified for tetracyclines which have led to widely divergent experimental and clinical uses. For example, tetracyclines are also an effective anti-malarial drug. Minocycline, which can readily cross cell membranes, is known to be a potent anti-apoptotic agent. Another tetracycline, doxycycline is known to exert anti-protease activities. Doxycycline can inhibit matrix metalloproteinases which contribute to tissue destruction activities in diseases such as periodontitis. A large body of literature has provided additional evidence for the “beneficial” actions of tetracyclines, including their ability to act as reactive oxygen species scavengers and anti-inflammatory agents. This review provides a summary of tetracyclines multiple mechanisms of action as a means to understand their beneficial effects.

Cardiac Uptake of Minocycline and Mechanisms for In Vivo Cardioprotection

OBJECTIVES The ability of minocycline to be transported into cardiac cells, concentrate in normal and ischemic myocardium, and act as a cardioprotector in vivo was examined. We also determined minocyclines capacity to act as a reducer of myocardial oxidative stress and matrix metalloproteinase (MMP) activity. BACKGROUND The identification of compounds with the potential to reduce myocardial ischemic injury is of great interest. Tetracyclines are antibiotics with pleiotropic cytoprotective properties that accumulate in normal and diseased tissues. Minocycline is highly lipophilic and has shown promise as a possible cardioprotector. However, minocyclines potential as an in vivo cardioprotector as well as the means by which this action is attained are not well understood. METHODS Rats were subjected to 45 min of ischemia and 48 h of reperfusion. Animals were treated 48 h before and 48 h after thoracotomy with either vehicle or 50 mg/kg/day minocycline. Tissue samples were used for biochemical assays and cultured cardiac cells for minocycline uptake experiments. RESULTS Minocycline significantly reduced infarct size (approximately 33%), tissue MMP-9 activity, and oxidative stress. Minocycline was concentrated approximately 24-fold in normal (0.5 mmol/l) and approximately 50-fold in ischemic regions (1.1 mmol/l) versus blood. Neonatal rat cardiac fibroblasts, myocytes, and adult fibroblasts demonstrated a time- and temperature-dependent uptake of minocycline to levels that approximate those of normal myocardium. CONCLUSIONS Given the high intracellular levels observed and results from the assessment of in vitro antioxidant and MMP inhibitor capacities, it is likely that minocycline acts to limit myocardial ischemic injury via mass action effects.

Reduction of myocardial infarct size by doxycycline: a role for plasmin inhibition.

Myocardial ischemia-reperfusion (I/R) is associated with the activation of matrix metalloproteinases (MMPs) and serine proteases. We hypothesized that activation of MMPs and the serine protease plasmin contribute to early cardiac myocyte death following I/R and that broad-spectrum protease inhibition with doxycycline (DOX) preserves myocyte viability. Rats treated daily with or without DOX beginning 48 h prior to experimentation were subjected to 30 min of coronary occlusion and 2 days of reperfusion. DOX pre-treatment reduced infarct size by 37%. DOX attenuated increases in MMP-9 and plasmin levels as determined by gelatin zymography and immunoblot, respectively. Neutrophil extravasation was unaltered by DOX as assessed by myeloperoxidase (MPO) activity. To examine the contribution of MMP-9 and plasmin to myocyte injury, cultures of neonatal rat ventricular myocytes (NRVMs) were treated for 48 h with 83 kDa MMP-9 or plasminogen in the presence or absence of DOX. MMP-9 treatment did not affect myocyte viability. Plasminogen treatment led to increased plasmin activity, resulting in loss of β1-integrin, NRVM detachment and apoptosis. DOX co-treatment inhibited plasmin activity and preserved NRVM attachment, whereas co-treatment with the broad-spectrum MMP inhibitor GM6001 had no effect. These results indicate that plasmin causes disruption of myocyte attachment and viability independently of MMP activation in vitro and that inhibition of plasmin by DOX may reduce I/R-induced myocyte death in vivo through the inhibition of plasmin. (Mol Cell Biochem 270: 1–11, 2005)

Dynamic Four-Dimensional MR Angiography of the Chest and Abdomen

Time-resolved (four-dimensional) contrast-enhanced MR angiography (CE-MRA) circumvents many of the adverse effects and limitations of conventional x-ray digital subtraction angiography. Four-dimensional CE-MRA uses improvements in gradient hardware, pulse sequences, or computational power to reduce scan times to seconds or less, allowing rapid sequential acquisitions within a single breath hold. These techniques eliminate the need for contrast bolus timing, ensure acquisition of the peak vascular phase of interest, and provide information on the dynamics of contrast arrival and hemodynamic consequences of complex vascular pathologies. This article reviews the techniques used to perform four-dimensional CE-MRA and provides an overview of how to use these techniques in CE-MRA of the chest and abdomen.

Locally advanced pancreas cancer: Staging and goals of therapy

Background: Patients with locally advanced pancreatic cancer have historically been considered inoperable. The purpose of this report was to determine resectability rates for patients with locally advanced pancreatic cancer based on our recently described definitions of type A and type B locally advanced pancreatic cancer. Methods: An institutional prospective pancreas cancer database was queried for consecutive patients with locally advanced pancreatic cancer treated between January 2009 and June 2017. All pretreatment imaging was re‐reviewed and patients were categorized as locally advanced pancreatic cancer type A or type B. Demographics, induction therapy, resection type, and outcomes were reviewed. Results: We identified 108 consecutive patients; 12 were excluded from analysis due to the absence of available pretreatment imaging or they had not yet completed all intended neoadjuvant therapy. Of the remaining 96 patients (45 type A, 51 type B), disease progression occurred in 19 (20%) during induction therapy and 30 (31%) were deemed inoperable at final preoperative restaging. Therefore, 47 (49%) of 96 patients were taken to surgery and 40 (42%) underwent successful resection (28 [62%] of 45 type A and 12 [24%] of 51 type B); an RO resection was achieved in 32 (80%). Metastatic disease was found intraoperatively (6 at laparoscopy, 1 at laparotomy) in 7 (15%) of 47 patients. There were no mortalities; 6 (15%) patients experienced major postoperative complications. Resected patients had a median overall survival of 38.9 months. Conclusion: Locally advanced pancreatic cancer can be dichotomized into type A and B with distinctly different probabilities of completing all therapy to include surgery; thereby allowing goals of therapy to be established at the time of diagnosis. Multimodality therapy that includes surgery can be accomplished in selected patients with locally advanced pancreatic cancer and is associated with a median overall survival that approximates earlier stages of disease. (Surgery 2017;160:XXX‐XXX.)