N-Terminomic Identification of Intracellular MMP-2 Substrates in Cardiac Tissue.

Proteases are enzymes that induce irreversible post-translational modifications by hydrolyzing amide bonds in proteins. One of these proteases is matrix metalloproteinase-2 (MMP-2), which has been shown to modulate extracellular matrix remodeling and intracellular proteolysis during myocardial injury. However, the substrates of MMP-2 in heart tissue are limited, and lesser known are the cleavage sites. Here, we used degradomics to investigate the substrates of intracellular MMP-2 in rat ventricular extracts. First, we designed a novel, constitutively active MMP-2 fusion protein (MMP-2-Fc) that we expressed and purified from mammalian cells. Using this protease, we proteolyzed ventricular extracts and used subtiligase-mediated N-terminomic labeling which identified 95 putative MMP-2-Fc proteolytic cleavage sites using mass spectrometry. The intracellular MMP-2 cleavage sites identified in heart tissue extracts were enriched for proteins primarily involved in metabolism, as well as the breakdown of fatty acids and amino acids. We further characterized the cleavage of three of these MMP-2-Fc substrates based on the gene ontology analysis. We first characterized the cleavage of sarco/endoplasmic reticulum calcium ATPase (SERCA2a), a known MMP-2 substrate in myocardial injury. We then characterized the cleavage of malate dehydrogenase (MDHM) and phosphoglycerate kinase 1 (PGK1), representing new cardiac tissue substrates. Our findings provide insights into the intracellular substrates of MMP-2 in cardiac cells, suggesting that MMP-2 activation plays a role in cardiac metabolism.

Data-Independent Acquisition Proteomics and N-Terminomics Methods Reveal Alterations in Mitochondrial Function and Metabolism in Ischemic-Reperfused Hearts.

Myocardial ischemia-reperfusion (IR) (stunning) injury triggers changes in the proteome and degradome of the heart. Here, we utilize quantitative proteomics and comprehensive degradomics to investigate the molecular mechanisms of IR injury in isolated rat hearts. The control group underwent aerobic perfusion, while the IR injury group underwent 20 min of ischemia and 30 min of reperfusion to induce a stunning injury. As MMP-2 activation has been shown to contribute to myocardial injury, hearts also underwent IR injury with ARP-100, an MMP-2-preferring inhibitor, to dissect the contribution of MMP-2 to IR injury. Using data-independent acquisition (DIA) and mass spectroscopy, we quantified 4468 proteins in ventricular extracts, whereby 447 proteins showed significant alterations among the three groups. We then used subtiligase-mediated N-terminomic labeling to identify more than a hundred specific cleavage sites. Among these protease substrates, 15 were identified following IR injury. We identified alterations in numerous proteins involved in mitochondrial function and metabolism following IR injury. Our findings provide valuable insights into the biochemical mechanisms of myocardial IR injury, suggesting alterations in reactive oxygen/nitrogen species handling and generation, fatty acid metabolism, mitochondrial function and metabolism, and cardiomyocyte contraction.

Novel methods for assessment of vulnerability to financial exploitation (FE).

Financial exploitation (FE) is a complex problem influenced by many factors. This article introduces two novel methods for assessment of FE vulnerability: (1) performance-based measures of financial skills using web-based simulations of common financial tasks; (2) scam vulnerability measures based on credibility ratings of common scam scenarios. Older adults who were male, younger, Hispanic, more educated, with higher incomes performed better on the simulated financial tasks. Better performance was also related to higher cognitive function and numeracy, and more experience with technology. On the scenario-based measures, older adults who were male, younger, African American, less educated, and lower income showed higher FE vulnerability. Higher scam vulnerability was also related to poorer performance on the simulated financial tasks, lower cognitive function, less experience with technology, more financial conflict/anxiety, more impulsivity, and more stranger-initiated FE. Findings indicate that these novel measures show promise as valid indicators of vulnerability to FE.

The roles of intracellular proteolysis in cardiac ischemia-reperfusion injury.

Ischemic heart disease remains a leading cause of human mortality worldwide. One form of ischemic heart disease is ischemia-reperfusion injury caused by the reintroduction of blood supply to ischemic cardiac muscle. The short and long-term damage that occurs due to ischemia-reperfusion injury is partly due to the proteolysis of diverse protein substrates inside and outside of cardiomyocytes. Ischemia-reperfusion activates several diverse intracellular proteases, including, but not limited to, matrix metalloproteinases, calpains, cathepsins, and caspases. This review will focus on the biological roles, intracellular localization, proteolytic targets, and inhibitors of these proteases in cardiomyocytes following ischemia-reperfusion injury. Recognition of the intracellular function of each of these proteases includes defining their activation, proteolytic targets, and their inhibitors during myocardial ischemia-reperfusion injury. This review is a step toward a better understanding of protease activation and involvement in ischemic heart disease and developing new therapeutic strategies for its treatment.

Matrix metalloproteinase-2 proteolyzes mitofusin-2 and impairs mitochondrial function during myocardial ischemia-reperfusion injury.

During myocardial ischemia and reperfusion (IR) injury matrix metalloproteinase-2 (MMP-2) is rapidly activated in response to oxidative stress. MMP-2 is a multifunctional protease that cleaves both extracellular and intracellular proteins. Oxidative stress also impairs mitochondrial function which is regulated by different proteins, including mitofusin-2 (Mfn-2), which is lost in IR injury. Oxidative stress and mitochondrial dysfunction trigger the NLRP3 inflammasome and the innate immune response which invokes the de novo expression of an N-terminal truncated isoform of MMP-2 (NTT-MMP-2) at or near mitochondria. We hypothesized that MMP-2 proteolyzes Mfn-2 during myocardial IR injury, impairing mitochondrial function and enhancing the inflammasome response. Isolated hearts from mice subjected to IR injury (30 min ischemia/40 min reperfusion) showed a significant reduction in left ventricular developed pressure (LVDP) compared to aerobically perfused hearts. IR injury increased MMP-2 activity as observed by gelatin zymography and increased degradation of troponin I, an intracellular MMP-2 target. MMP-2 preferring inhibitors, ARP-100 or ONO-4817, improved post-ischemic recovery of LVDP compared to vehicle perfused IR hearts. In muscle fibers isolated from IR hearts the rates of mitochondrial oxygen consumption and ATP production were impaired compared to those from aerobic hearts, whereas ARP-100 or ONO-4817 attenuated these reductions. IR hearts showed higher levels of NLRP3, cleaved caspase-1 and interleukin-1ß in the cytosolic fraction, while the mitochondria-enriched fraction showed reduced levels of Mfn-2, compared to aerobic hearts. ARP-100 or ONO-4817 attenuated these changes. Co-immunoprecipitation showed that MMP-2 is associated with Mfn-2 in aerobic and IR hearts. ARP-100 or ONO-4817 also reduced infarct size and cell death in hearts subjected to 45 min ischemia/120 min reperfusion. Following myocardial IR injury, impaired contractile function and mitochondrial respiration and elevated inflammasome response could be attributed, at least in part, to MMP-2 activation, which targets and cleaves mitochondrial Mfn-2. Inhibition of MMP-2 activity protects against cardiac contractile dysfunction in IR injury in part by preserving Mfn-2 and suppressing inflammation.

An interferon gamma response signature links myocardial aging and immunosenescence.

AIMS: Aging entails profound immunological transformations that can impact myocardial homeostasis and predispose to heart failure. However, preclinical research in the immune-cardiology field is mostly conducted in young healthy animals, which potentially weakens its translational relevance. Herein, we sought to investigate how the aging T-cell compartment associates with changes in myocardial cell biology in aged mice. METHODS AND RESULTS: We phenotyped the antigen-experienced effector/memory T cells purified from heart-draining lymph nodes of 2-, 6-, 12-, and 18-month-old C57BL/6J mice using single-cell RNA/T cell receptor sequencing. Simultaneously, we profiled all non-cardiomyocyte cell subsets purified from 2- to 18-month-old hearts and integrated our data with publicly available cardiomyocyte single-cell sequencing datasets. Some of these findings were confirmed at the protein level by flow cytometry. With aging, the heart-draining lymph node and myocardial T cells underwent clonal expansion and exhibited an up-regulated pro-inflammatory transcription signature, marked by an increased interferon-γ (IFN-γ) production. In parallel, all major myocardial cell populations showed increased IFN-γ responsive signature with aging. In the aged cardiomyocytes, a stronger IFN-γ response signature was paralleled by the dampening of expression levels of transcripts related to most metabolic pathways, especially oxidative phosphorylation. Likewise, induced pluripotent stem cells-derived cardiomyocytes exposed to chronic, low grade IFN-γ treatment showed a similar inhibition of metabolic activity. CONCLUSIONS: By investigating the paired age-related alterations in the T cells found in the heart and its draining lymph nodes, we provide evidence for increased myocardial IFN-γ signaling with age, which is associated with inflammatory and metabolic shifts typically seen in heart failure.

Evaluation of Face Validity and Acceptability of the Care Partner Hospital Assessment Tool.

Background and Objectives: Care partners of hospitalized older adults report their caregiving needs are not being addressed. The Care Partner Hospital Assessment Tool (CHAT) is a feasible and appropriate tool for practitioners' use with care partners in the hospital setting. This article explores the face validity and acceptability of the CHAT among care partners of hospitalized older adults. Research Design and Methods: A qualitative descriptive study was used to identify common themes among care partners' responses from semistructured interviews. The CHAT was administered to care partners of older adults admitted to a medical-surgical unit in an academic medical center in Madison, WI, from October 2021 to January 2022. A semistructured, follow-up interview was completed by the same care partners after discharge. Interviews were transcribed and coded for themes to capture overall impressions of the CHAT. Care partners addressed the usefulness, comfort, content, and complexity of the CHAT. Results: Twelve care partners participated in the study. Care partners reported that the CHAT was easy to understand and complete, was judged to be useful to both the care partner and older adult, and helped identify care partner needs. Care partners suggested ways to improve the tool including administration, additional content areas to include, and modes of delivery. Discussion and Implications: The results establish the face validity of the CHAT and support the acceptability of the tool for use with care partners of hospitalized older adults.

Effects of Childcare, Work, and Caregiving Intensity on Male and Female Family Caregivers.

OBJECTIVES: The Behavioral Risk Factor Surveillance System sampled 54,076 caregivers between 2015 and 2017 providing an opportunity to evaluate risk factors for poor mental and physical health among a representative sample of U.S. adult caregivers. This study aimed to evaluate the impact of childcare, work status, and intensity of caregiving among men and women caring for older adults (n = 17,271). METHODS: Controlling for sociodemographic factors, separate logistic regression analysis for women and men were carried out to assess the main and interaction effects of childcare, work status, and intensity of caregiving on number of poor mental and physical health days in the last month. RESULTS: Intensive caregiving demands had adverse effects on both women and men, but being in the workforce was beneficial to both men and women. Women with children at home reported adverse mental health effects but better physical health, while men with children at home reported adverse physical health effects. For women, the combination of not working, children in the household, and high-intensity caregiving were most detrimental to their mental health. Among men, those not working with children in the household, regardless of caregiving intensity, were at highest risk of adverse mental health effects. DISCUSSION: Our findings identify caregivers at high risk of adverse outcomes but also point to the need for more fine-grained analyses of how families negotiate the allocation of childcare, work, and caregiving responsibilities over time.

Out-of-Pocket Health Care Spending at Older Ages: Do Caregiving Arrangements Matter?

Identifying the correlates of out-of-pocket (OOP) health care spending is an important step for ensuring the financial security of older adults. Whether or not someone has a family member providing assistance is one such factor that could be associated with OOP spending. If family caregivers facilitate better health, health care spending could be reduced. On the other hand, costs would be higher if family members facilitate more (or more costly) care for loved ones. This paper explores the relationship between caregiving arrangements and OOP spending using data from 5045 individuals in the 2000-2016 Health and Retirement Study with Medicare coverage and caregiving needs. We do not find a relationship between family caregiving and OOP health care costs, overall. However, among those with Medicare HMO insurance, having a family caregiver is associated with more spending than having no helper. This is mainly due to differences in spending on prescription medications.

Activity patterns related to depression symptoms in stressed dementia caregivers.

OBJECTIVES: Self-reported activity restriction is an established correlate of depression in dementia caregivers (dCGs). It is plausible that the daily distribution of objectively measured activity is also altered in dCGs with depression symptoms; if so, such activity characteristics could provide a passively measurable marker of depression or specific times to target preventive interventions. We therefore investigated how levels of activity throughout the day differed in dCGs with and without depression symptoms, then tested whether any such differences predicted changes in symptoms 6 months later. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: We examined 56 dCGs (mean age = 71, standard deviation (SD) = 6.7; 68% female) and used clustering to identify subgroups which had distinct depression symptom levels, leveraging baseline Center for Epidemiologic Studies of Depression Scale-Revised Edition and Patient Health Questionnaire-9 (PHQ-9) measures, as well as a PHQ-9 score from 6 months later. Using wrist activity (mean recording length = 12.9 days, minimum = 6 days), we calculated average hourly activity levels and then assessed when activity levels relate to depression symptoms and changes in symptoms 6 months later. RESULTS: Clustering identified subgroups characterized by: (1) no/minimal symptoms (36%) and (2) depression symptoms (64%). After multiple comparison correction, the group of dCGs with depression symptoms was less active from 8 to 10 AM (Cohen's d ≤ -0.9). These morning activity levels predicted the degree of symptom change on the PHQ-9 6 months later (per SD unit ß = -0.8, 95% confidence interval: -1.6, -0.1, p = 0.03) independent of self-reported activity restriction and other key factors. CONCLUSIONS: These novel findings suggest that morning activity may protect dCGs from depression symptoms. Future studies should test whether helping dCGs get active in the morning influences the other features of depression in this population (i.e. insomnia, intrusive thoughts, and perceived activity restriction).

The Role of Preparedness for Caregiving on the Relationship Between Caregiver Distress and Potentially Harmful Behaviors.

This work extends research suggesting a link between indicators of distress among informal caregivers (CG) (e.g., depression and burden), and potentially harmful behaviors (PHB), including feeling like yelling or screaming at the care recipient (CR). We tested three hypotheses regarding the role of a novel predictor, CG preparedness for caregiving, which were: 1) a direct effect between CG preparedness and PHB, 2) CG distress mediates the relationship between the direct effect of CG preparedness on PHB, and finally, 3) CG preparedness is only related to PHB through their shared associations with indicators of caregiver distress, an indirect effects model. Examining two indicators of PHB and CG depression and CG burden, results supported the indirect effects model. Higher CG preparedness was associated with lower CG distress, which in turn was associated with lower risk of PHB. These findings highlight the importance of CG preparedness as a target for caregiver intervention research.

Call for Consensus in the Evaluation of Circulating Matrix Metalloproteinases in Chagas Disease.

Infection with the Trypanosoma cruzi parasite is endemic in parts of America. Approximately 30% of people infected develop Chagas cardiomyopathy, the most common cause of heart failure in these regions. No suitable biomarker that reflects the evolution of the disease has been widely accepted as of yet. There is substantial evidence, however, of a strong inflammatory reaction following infection with T. cruzi that could activate matrix metalloproteinases (MMPs). Emerging research suggests the involvement of MMPs in Chagas cardiomyopathy and there is a growing interest in measuring the blood levels of MMPs as diagnostic and/or prognostic indicators of heart damage in Chagas patients. This perspective discusses the lack of consensus on the best method for MMP evaluation. Some studies are based on MMP concentrations and activities in serum whereas others use plasma. We believe that these different methods of evaluation have led to incongruent and poorly comparable data on the blood levels of MMPs in Chagas patients. A standard for the preparation of blood samples needs to be adopted for the study of MMPs as markers of Chagas cardiomyopathy to ensure better comparability of research results.

Staurosporine-induced cleavage of apoptosis-inducing factor in human fibrosarcoma cells is independent of matrix metalloproteinase-2.

Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein which mediates staurosporine (STS) - induced cell death. AIF cleavage and translocation to the cytosol is thought to be calpain-1-dependent as calpain inhibitors reduce AIF proteolysis; however, many calpain inhibitors also inhibit matrix metalloproteinase-2 (MMP-2) activity, an intracellular and extracellular protease implicated in apoptosis. Here we investigated whether MMP-2 activity is affected in response to STS and if it contributes to AIF cleavage. Human fibrosarcoma HT1080 cells were treated with STS (0.1 µM, 0.25-24 h). A significant increase in cellular MMP-2 activity was seen by gelatin zymography after a 6 h STS treatment, prior to induction of cell necrosis. Western blot showed the time-dependent appearance of two forms of AIF (∼60 and 45 kDa) in the cytosol which were significantly increased at 6 h. Surprisingly, knocking down MMP-2 or inhibiting its activity with MMP-2 preferring inhibitors ARP-100 or ONO-4817, or inhibiting calpain activity with ALLM or PD150606, did not prevent the STS-induced increase in cytosolic AIF. These results show that although STS rapidly increases MMP-2 activity, the cytosolic release of AIF may be independent of the proteolytic activities of MMP-2 or calpain.

Compassion in dementia caregiving: Psychometric properties of the Caregiving Compassion Scale in Spanish caregivers.

Compassion has been suggested as a relevant variable for understanding dementia caregivers' psychological distress. The objectives were to analyse the psychometric properties of the Caregiving Compassion Scale (CCS) and to explore the association between caregivers' compassion and their emotional health. Two hundred and thirty-six dementia caregivers were evaluated for compassion, depressive symptoms, guilt, ambivalence, care-recipient's functional and cognitive status, frequency of behavioural problems and desire to institutionalise the care-recipient. Exploratory factor analyses, correlations and regression analyses were done. Two factors were obtained. The factor labelled "Distress from witnessing the care recipient suffering" was associated with higher stress linked to witness depressive problems in the care-recipient and with caregivers' ambivalence and guilt levels. The factor labelled "Motivation/disposition for helping" was associated with less desire for institutionalisation, and it showed a negative association with ambivalence and guilt feelings. The CCS seems to be a valid and reliable scale for assessing compassion in dementia caregivers.

Matrix Metalloproteinase-2 Inhibition in Acute Ischemia-Reperfusion Heart Injury-Cardioprotective Properties of Carvedilol.

Matrix metalloproteinase 2 (MMP-2) is activated in hearts upon ischemia-reperfusion (IR) injury and cleaves sarcomeric proteins. It was shown that carvedilol and nebivolol reduced the activity of different MMPs. Hence, we hypothesized that they could reduce MMPs activation in myocytes, and therefore, protect against cardiac contractile dysfunction related with IR injury. Isolated rat hearts were subjected to either control aerobic perfusion or IR injury: 25 min of aerobic perfusion, followed by 20 min global, no-flow ischemia, and reperfusion for 30 min. The effects of carvedilol, nebivolol, or metoprolol were evaluated in hearts subjected to IR injury. Cardiac mechanical function and MMP-2 activity in the heart homogenates and coronary effluent were assessed along with troponin I content in the former. Only carvedilol improved the recovery of mechanical function at the end of reperfusion compared to IR injury hearts. IR injury induced the activation and release of MMP-2 into the coronary effluent during reperfusion. MMP-2 activity in the coronary effluent increased in the IR injury group and this was prevented by carvedilol. Troponin I levels decreased by 73% in IR hearts and this was abolished by carvedilol. Conclusions: These data suggest that the cardioprotective effect of carvedilol in myocardial IR injury may be mediated by inhibiting MMP-2 activation.

Evaluating the Appropriateness and Feasibility of the Care Partner Hospital Assessment Tool (CHAT).

Hospital practitioners rely on care partners of older adults to provide complex care without identifying and addressing their needs. The Care Partner Hospital Assessment Tool (CHAT) was developed to identify the education skill training needs of care partners of hospitalized older adults. This two-phased mixed-method study evaluated the appropriateness and feasibility of the CHAT. The phase 1 quantitative survey with caregiving experts indicated 70-100% agreement for the length and helpfulness of the CHAT (n = 23). These results were supported by phase 2 qualitative interviews with hospital administrators and practitioners, which revealed the following themes: (1) intuitive and clear design worth sustaining and (2) concerns and proposed solutions for implementation. Findings suggest the CHAT is an appropriate and feasible tool for hospital practitioners to tailor their education and skills training to address care partners' needs. Identifying care partners' needs is an important step in ensuring they are prepared to complete their caregiving responsibilities.

The Development and Content Validation of the Care Partner Hospital Assessment Tool.

BACKGROUND/OBJECTIVES: When aging adults are hospitalized due to a major health event, they often turn to care partners ('family members or friends') for support. Assessment of care partners' needs during hospital care may be important to inform and target information and skills training that will equip them to fulfill caregiving tasks for the aging adults. The objectives of this study were to develop and complete content validation of the Care Partner Hospital Assessment Tool (CHAT). METHODS: Based on standard instrumentation methodology and an assessment framework recommended by the National Center on Caregiving at the Family Caregiving Alliance, three steps were followed to develop and validate CHAT: (1) generation of a 24-item tool grouped into three content domains (background, plans and preferences, skills and supports), and a survey by a multidisciplinary team, (2) administration of an online survey of care partners and experts, and (3) assessment of item and scale-content validity indices (I-CVI and S-CVI). RESULTS: A total of four care partners that provide unpaid care to a family member or friend age 65 years or older with a chronic illness or disability either before or after a hospitalization, and 19 leading experts in gerontology, caregiving, and health services completed an online survey in English. Twenty-two items were accepted by having an I-CVI at or above the acceptable 78% cut point; the S-CVI for the tool was 85%. Most revisions to the tool were associated with modifying or clarifying language within each item. For example, participants shared the following open-ended suggestions for revising CHAT: (1) change the "do you prefer" sentence stem to "do you want" (n = 12), define "training" (n = 6), and (2) allow care partners to provide an unsure response (n = 5). CONCLUSION: CHAT may be a promising way to increase health care practitioner's understanding of care partners' backgrounds, preferences and plans, and potential information or training needs during a patient's hospital stay. Initial evaluation of CHAT reveals strong conceptual development and content validity.

Assessment of Oral Chemotherapy Nonadherence in Chronic Myeloid Leukemia Patients Using Brief Measures in Community Cancer Clinics: A Pilot Study.

The purpose of this pilot study was to assess Chronic Myeloid Leukemia (CML) patients' adherence to, beliefs about, and barriers to oral anticancer agents (OAC) using brief self-report measures in community-based cancer clinics. Patients completed a structured interview including a health literacy assessment, a Brief Medication Questionnaire, two single-item self-report adherence questions, and the Medications Adherence Reasons Scale. Of the 86 participants, 88.4% were white; 55.8% male; mean age, 58.7 years; and 22.1% had limited health literacy. Nonadherence (missing at least one dose in the last week) was reported by 18.6% of participants and associated (p < 0.003) with less-than-excellent perceived ability to take CML medications (16.3%). Black participants reported more difficulty taking CML medications than white participants (28.6% vs. 8.3%, p = 0.053). Among all participants, 43.0% reported their CML medicine was ineffective and 24.4% that taking CML pills was somewhat to very hard. The most common reasons for missing a dose were simply missed it (24.4%) and side effects (18.6%). Most patients perceived their ability to take CML medication was good to excellent, yet nearly one in five reported missing at least one dose in the last week. Brief, no-cost self-report assessments to screen CML patients' OAC adherence, barriers, and beliefs could facilitate counseling in busy community cancer clinics.

MMP inhibition attenuates hypertensive eccentric cardiac hypertrophy and dysfunction by preserving troponin I and dystrophin.

PURPOSE: Cardiac transition from concentric (C-LVH) to eccentric left ventricle hypertrophy (E-LVH) is a maladaptive response of hypertension. Matrix metalloproteinases (MMPs), in particular MMP-2, may contribute to tissue remodeling by proteolyzing extra- and intracellular proteins. Troponin I and dystrophin are two potential targets of MMP-2 examined in this study and their proteolysis would impair cardiac contractile function. We hypothesized that MMP-2 contributes to the decrease in troponin I and dystrophin in the hypertensive heart and thereby controls the transition from C-LVH to E-LVH and cardiac dysfunction. METHODS: Male Wistar rats were divided into sham or two kidney-1 clip (2K-1C) hypertensive groups and treated with water (vehicle) or doxycycline (MMP inhibitor, 15 mg/kg/day) by gavage from the tenth to the sixteenth week post-surgery. Tail-cuff plethysmography, echocardiography, gelatin zymography, confocal microscopy, western blot, mass spectrometry, in silico protein analysis and immunofluorescence were performed. RESULTS: 6 out of 23 2K-1C rats (26%) had E-LVH followed by reduced ejection fraction. The remaining had C-LVH with preserved cardiac function. Doxycycline prevented the transition from C-LVH to E-LVH. MMP activity is increased in C-LVH and E-LVH hearts which was inhibited by doxycycline. This effect was associated with an increase in troponin I cleavage products and a decline in dystrophin in the left ventricle of E-LVH rats, which was prevented by doxycycline. CONCLUSION: Hypertension causes increased cardiac MMP-2 activity which proteolyzes troponin I and dystrophin, contributing to the transition from C-LVH to E-LVH and cardiac dysfunction.