The need for selective matrix metalloproteinase (MMP) inhibition is of interest because of the range of pathologies mediated by different MMP isoforms. The development of more selective MMP inhibitors (MMPi) may help to overcome some of the undesired side effects that have hindered the clinical success of these compounds. In an effort to devise new approaches to selective inhibitors, herein we describe several novel MMPi and show that their selectivity is dependent on the nature of the zinc-binding group (ZBG). This is in contrast to most current MMPi, which obtain isoform selectivity solely from the peptidomimetic backbone portion of the compound. In the present study, six different hydroxypyrone and hydroxypyridinone ZBGs were appended to a common biphenyl backbone and the inhibition efficiency of each inhibitor was determined in vitro (IC(50) values) against MMP-1, -2, -3, -7, -8, -9, -12, and -13. The results show that the selectivity profile of each inhibitor is different as a result of the various ZBGs. Computational modeling studies were used to explain some trends in the observed selectivity profiles. To assess the importance of the ZBG in a biological model, two of the semiselective, potent MMPi (and one control) were evaluated using an isolated perfused rat heart system. Hearts were subjected to ischemia reperfusion injury, and recovery of contractile function was examined. In this model, only one of the two MMPi showed significant and sustained heart recovery, demonstrating that the choice of ZBG can have a significant effect in a relevant pathophysiological endpoint.

In an effort to improve the zinc-chelating portion of matrix metalloproteinase (MMP) inhibitors, we have developed a family of heterocyclic zinc-binding groups (ZBGs) as alternatives to the widely used hydroxamic acid moiety. Elaborating on findings from an earlier report, we performed in vitro inhibition assays with recombinant MMP-1, MMP-2, and in a cell culture assay using neonatal rat cardiac fibroblast cells. In both recombinant and cell culture assays, the new ZBGs were found to be effective inhibitors, typically 10-100-fold more potent than acetohydroxamic acid. The toxicity of these chelators was examined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt cytotoxicity assays, which demonstrate that most of these compounds are nontoxic at concentrations of almost 100 microM. To address the possible interaction of sulfur-containing ZBGs with biological reductants, the reactivity of these chelators with 5,5'-dithiobis(2-nitrobenzoic acid) was examined. Finally, thione ZBGs were shown to be effective inhibitors of cell invasion through an extracellular matrix membrane. The data presented herein suggest these heterocyclic ZBGs are potent, nontoxic, and biocompatible compounds that show promise for incorporation into a new family of MMP inhibitors.

Epidemiological studies have shown a correlation between flavonoid-rich diets and improved cardiovascular prognosis. Cocoa contains large amounts of flavonoids, in particular flavanols (mostly catechins and epicatechins). Flavonoids possess pleiotropic properties that may confer protective effects to tissues during injury. We examined the ability of epicatechin to reduce short-and long-term ischemia-reperfusion (I/R) myocardial injury. Epicatechin (1 mg.kg(-1).day(-1)) pretreatment (Tx) was administered daily via oral gavage to male rats for 2 or 10 days. Controls received water. Ischemia was induced via a 45-min coronary occlusion. Reperfusion was allowed until 48 h or 3 wk while Tx continued. We measured infarct (MI) size (%), hemodynamics, myeloperoxidase activity, tissue oxidative stress, and matrix metalloproteinase-9 (MMP-9) activity in 48-h groups. Cardiac morphometry was also evaluated in 3-wk groups. With 2 days of Tx, no reductions in MI size occurred. After 10 days, a significant approximately 50% reduction in MI size occurred. Epicatechin rats demonstrated no significant changes in hemodynamics. Tissue oxidative stress was reduced significantly in the epicatechin group vs. controls. MMP-9 activity demonstrated limited increases in the infarct region with epicatechin. By 3 wk, a significant 32% reduction in infarct size was observed with Tx, accompanied with sustained hemodynamics and preserved chamber morphometry. In conclusion, epicatechin Tx confers cardioprotection in the setting of I/R injury. The effects are independent of changes in hemodynamics, are sustained over time, and are accompanied by reduced levels of indicators of tissue injury. Results warrant the evaluation of cocoa flavanols as possible therapeutic agents to limit ischemic injury.

Objectives The ability of minocycline to be transported into cardiac cells, concentrate in normal and ischemic myocardium and act as in vivo cardioprotector was examined. We also determined minocycline's 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 (TTCs) 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, minocycline's 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 (∼33%), tissue MMP-9 activity and oxidative stress. Minocycline was concentrated ∼24-fold in normal (0.5 mM) and ∼50-fold in ischemic regions (1.1 mM) vs. blood. Neonatal rat cardiac fibroblasts, myocytes and adult fibroblasts demonstrate 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.

Nonaqueous high internal phase emulsions (HIPEs) stabilized by nanohydroxyapatite (NHA)/surfactant hybrids are used as template to prepare interconnected porous monoliths. The use of a sustainable deep eutectic solvent (DES) comprised of urea and choline chloride (UChCl), as the internal phase, enables an efficient interaction of NHA/surfactant at the HIPE interface, which in turn allows for a bottom‐up approach to selective interfacial functionalization of poly(HIPE's) voids surface after polymerization of methyl methacrylate continuous phase. UChCl DES is a suitable internal phase for HIPE polymerization thanks to its polarity and viscosity that provides further stabilization of the emulsion precursor. This simple synthetic method produces well‐defined functional poly(methyl methacrylate) (pMMA) scaffolds with tunable mechanical properties and exposed NHA at the inner surface. Based upon a preliminary biocompatibility in vivo test, poly(HIPEs) show enhanced biocompatibility in comparison with sterile gauze. Interestingly, pMMA NHA nanocomposite scaffold remains in the tissue after 90 d allowing little ingrowth of cells while causing a normal foreign‐body reaction in the rats' muscle tissue. Interfacial functionalization of well‐defined interconnected porous monoliths with nanomaterials via DES‐based HIPEs approach is a promising method that encourages further investigation for the synthesis of biodegradable and biocompatible scaffolds nanocomposites for tissue engineering purposes.