1 Division of Geriatric Medicine, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan; and 2 Institute of Molecular Cardiology, University of Louisville, Louisville, ...Kentucky
Submitted 9 June 2008
; accepted in final form 14 October 2008
Ischemic tolerance decreases with aging, and the cardioprotective effect of ischemic preconditioning (IPC) is impaired in middle-aged animals. We have demonstrated that short-term caloric restriction (CR) improves myocardial ischemic tolerance in young and old animals via the activation of adiponectin-AMP-activated protein kinase (AMPK)-mediated signaling. However, it is unknown whether prolonged CR confers cardioprotection in a similar manner. Furthermore, little is known regarding the myocardial expression of silent information regulator 1 (Sirt1; which reportedly mediates various aspects of the CR response) with prolonged CR. Thus, 6-mo-old male Fischer-344 rats were randomly divided into ad libitum (AL) and CR groups. Six months later, isolated perfused hearts were subjected to 25 min of global ischemia followed by 120 min of reperfusion with or without IPC. CR improved the recovery of left ventricular function and reduced infarct size after ischemia-reperfusion and restored the IPC effect. Serum adiponectin levels increased, but myocardial levels of total and phosphorylated AMPK did not change with prolonged CR. Total levels of Sirt1 did not change with CR; however, in the nuclear fraction, CR significantly increased Sirt1 and decreased acetyl-histone H3. Eleven rats from each group were given N -nitro- L -arginine methyl ester in their drinking water for 4 wk before death. In these hearts, chronic inhibition of nitric oxide synthase prevented the increase in nuclear Sirt1 content by CR and abrogated CR-induced cardioprotection. These results demonstrate that 1 ) prolonged CR improves myocardial ischemic tolerance and restores the IPC effect in middle-aged rats and 2 ) CR-induced cardioprotection is associated with a nitric oxide-dependent increase in nuclear Sirt1 content.
aging; myocardial ischemia; nutrition; preconditioning; reperfusion injury; silent information regulator 1
Address for reprint requests and other correspondence: K. Shinmura, Div. of Geriatric Medicine, Dept. of Internal Medicine, Keio Univ. School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan (e-mail: shimmura{at}sc.itc.keio.ac.jp )
Myocardial ischemia-reperfusion (I/R) results in the generation of free radicals, accumulation of lipid peroxidation-derived unsaturated aldehydes, variable angina (pain), and infarction. The ...transient receptor potential ankyrin 1 (TRPA1) mediates pain signaling and is activated by unsaturated aldehydes, including acrolein and 4-hydroxynonenal. The contribution of TRPA1 (a Ca
-permeable channel) to I/R-induced myocardial injury is unknown. We tested the hypothesis that cardiac TRPA1 confers myocyte sensitivity to aldehyde accumulation and promotes I/R injury. Although basal cardiovascular function in TRPA1-null mice was similar to that in wild-type (WT) mice, infarct size was significantly smaller in TRPA1-null mice than in WT mice (34.1 ± 9.3 vs. 14.3 ± 9.9% of the risk region, n = 8 and 7, respectively, P < 0.05), despite a similar I/R-induced area at risk (40.3 ±8.4% and 42.2 ± 11.3% for WT and TRPA1-null mice, respectively) after myocardial I/R (30 min of ischemia followed by 24 h of reperfusion) in situ. Positive TRPA1 immunofluorescence was present in murine and human hearts and was colocalized with connexin43 at intercalated disks in isolated murine cardiomyocytes. Cardiomyocyte TRPA1 was confirmed by quantitative RT-PCR, DNA sequencing, Western blot analysis, and electrophysiology. A role of TRPA1 in cardiomyocyte toxicity was demonstrated in isolated cardiomyocytes exposed to acrolein, an I/R-associated toxin that induces Ca
accumulation and hypercontraction, effects significantly blunted by HC-030031, a TRPA1 antagonist. Protection induced by HC-030031 was quantitatively equivalent to that induced by SN-6, a Na
/Ca
exchange inhibitor, further supporting a role of Ca
overload in acrolein-induced cardiomyocyte toxicity. These data indicate that cardiac TRPA1 activation likely contributes to I/R injury and, thus, that TRPA1 may be a novel therapeutic target for decreasing myocardial I/R injury. NEW & NOTEWORTHY Transient receptor potential ankyrin 1 (TRPA1) activation mediates increased blood flow, edema, and pain reception, yet its role in myocardial ischemia-reperfusion (I/R) injury is unknown. Genetic ablation of TRPA1 significantly decreased myocardial infarction after I/R in mice. Functional TRPA1 in cardiomyocytes was enriched in intercalated disks and contributed to acrolein-induced Ca
overload and hypercontraction. These data indicate that I/R activation of TRPA1 worsens myocardial infarction; TRPA1 may be a potential target to mitigate I/R injury.
Although transplantation of c-kit+ cardiac stem cells (CSCs) has been shown to alleviate left ventricular (LV) dysfunction induced by myocardial infarction (MI), the number of exogenous CSCs ...remaining in the recipient heart following transplantation and their mechanism of action remain unclear. We have previously developed a highly sensitive and accurate method to quantify the absolute number of male murine CSCs in female recipient organs after transplantation. In the present study, we used this method to monitor the number of donor CSCs in the recipient heart after intracoronary infusion. Female mice underwent a 60-min coronary occlusion followed by reperfusion; 2 days later, 100,000 c-kit+/lin- syngeneic male mouse CSCs were infused intracoronarily. Only 12.7% of the male CSCs present in the heart immediately (5 min) after infusion were still present in the heart at 24 h, and their number declined rapidly thereafter. By 35 days after infusion, only ∼ 1,000 male CSCs were found in the heart. Significant numbers of male CSCs were found in the lungs and kidneys, but only in the first 24 h. The number of CSCs in the lungs increased between 5 min and 24 h after infusion, indicating recirculation of CSCs initially retained in other organs. Despite the low retention and rapid disappearance of CSCs from the recipient heart, intracoronary delivery of CSCs significantly improved LV function at 35 days (Millar catheter). These results suggest that direct differentiation of CSCs alone cannot account for the beneficial effects of CSCs on LV function; therefore, paracrine effects must be the major mechanism. The demonstration that functional improvement is dissociated from survival of transplanted cells has major implications for our understanding of cell therapy. In addition, this new quantitative method of stem cell measurement will be useful in testing approaches of enhancing CSC engraftment and survival after transplantation.
Experimental Research Laboratory, Division of Cardiology,
University of Louisville, Louisville, Kentucky; and Section of
Molecular and Cellular Cardiology, Department of Medicine, Johns
Hopkins ...University, Baltimore, Maryland
Bolli, Roberto and
Eduardo Marbán.
The past two decades have witnessed an explosive
growth of knowledge regarding postischemic myocardial dysfunction or
myocardial "stunning." The purpose of this review is to summarize
current information regarding the pathophysiology and pathogenesis of this phenomenon. Myocardial stunning should not be regarded as a single
entity but rather as a "syndrome" that has been observed in a wide
variety of experimental settings, which include the following:
1 ) stunning after a single, completely reversible episode of
regional ischemia in vivo; 2 ) stunning after multiple,
completely reversible episodes of regional ischemia in vivo;
3 ) stunning after a partly reversible episode of regional
ischemia in vivo (subendocardial infarction); 4 ) stunning
after global ischemia in vitro; 5 ) stunning after global
ischemia in vivo; and 6 ) stunning after exercise-induced
ischemia (high-flow ischemia). Whether these settings share a common
mechanism is unknown. Although the pathogenesis of myocardial stunning
has not been definitively established, the two major hypotheses are
that it is caused by the generation of oxygen-derived free radicals
(oxyradical hypothesis) and by a transient calcium overload (calcium
hypothesis) on reperfusion. The final lesion responsible for the
contractile depression appears to be a decreased responsiveness of
contractile filaments to calcium. Recent evidence suggests that calcium
overload may activate calpains, resulting in selective proteolysis of
myofibrils; the time required for resynthesis of damaged proteins would
explain in part the delayed recovery of function in stunned myocardium.
The oxyradical and calcium hypotheses are not mutually exclusive and
are likely to represent different facets of the same pathophysiological
cascade. For example, increased free radical formation could cause
cellular calcium overload, which would damage the contractile apparatus of the myocytes. Free radical generation could also directly alter contractile filaments in a manner that renders them less responsive to
calcium (e.g., oxidation of critical thiol groups). However, it remains
unknown whether oxyradicals play a role in all forms of stunning and
whether the calcium hypothesis is applicable to stunning in vivo.
Nevertheless, it is clear that the lesion responsible for myocardial
stunning occurs, at least in part, after reperfusion so that this
contractile dysfunction can be viewed, in part, as a form of
"reperfusion injury." An important implication of the phenomenon of
myocardial stunning is that so-called chronic hibernation may in
fact be the result of repetitive episodes of stunning, which have a
cumulative effect and cause protracted postischemic dysfunction. A
better understanding of myocardial stunning will expand our knowledge
of the pathophysiology of myocardial ischemia and provide a rationale
for developing new therapeutic strategies designed to prevent
postischemic dysfunction in patients.
Given the rising prevalence of cardiovascular disease worldwide and the limited therapeutic options for severe heart failure, novel technologies that harness the regenerative capacity of the heart ...are sorely needed. The therapeutic use of stem cells has the potential to reverse myocardial injury and improve cardiac function, in contrast to most current medical therapies that only mitigate heart failure symptoms. Nearly 2 decades and >200 trials for cardiovascular disease have revealed that most cell types are safe; however, their efficacy remains controversial, limiting the transition of this therapy from investigation to practice. Lessons learned from these initial studies are driving the design of new clinical trials; higher fidelity of cell isolation techniques, standardization of conditions, more consistent use of state of the art measurement techniques, and assessment of multiple end points to garner insights into the efficacy of stem cells. Translation to clinical trials has almost outpaced our mechanistic understanding, and individual patient factors likely play a large role in stem cell efficacy. Therefore, careful analysis of dosing, delivery methods, and the ideal patient populations is necessary to translate cell therapy from research to practice. We are at a pivotal stage in the field in which information from many relatively small clinical trials must guide carefully executed efficacy trials. Larger efficacy trials are being launched to answer questions about older, first-generation stem cell therapeutics, while novel, second-generation products are being introduced into the clinical realm. This review critically examines the current state of clinical research on cell-based therapies for cardiovascular disease, highlighting the controversies in the field, improvements in clinical trial design, and the application of exciting new cell products.
New Paradigms in Cell Therapy Wysoczynki Marcin; Khan, Abdur; Bolli, Roberto
Circulation research,
07/2018, Letnik:
123, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Perhaps the most important advance in the field of cell therapy for heart disease has been the recognition that all stem/progenitor cells (both adult and embryonic) fail to engraft in the heart to a ...significant extent and thus work via paracrine mechanisms. This fundamental advance has led to 4 new paradigms that are discussed in this review and that may importantly shape, or even revolutionize, the future of the field: (1) repeated cell therapy, (2) intravenous cell therapy, (3) immunomodulatory actions of cell therapy, and (4) new cell types. Because virtually all of our current knowledge of cell therapy is predicated on the effects of a single cell dose, the idea that the full therapeutic effects of a cell product require repeated doses is disruptive and has far-reaching implications. For example, inadequate dosing (single-dose protocols) may be responsible, at least in part, for the borderline or disappointing results obtained to date in clinical trials; furthermore, future studies (both preclinical and clinical) may need to incorporate repeated cell administrations. Another disruptive idea, supported by emerging preclinical and clinical evidence, is that intravenously injected cells can produce beneficial effects on the heart, presumably via release of paracrine factors in extracardiac organs or endocrine factors into the systemic circulation. Intravenous administration would obviate the need for direct delivery of cells to the heart, making cell therapy simpler, cheaper, safer, more scalable, and more broadly available, even on an outpatient basis. Although the mechanism of action of cell therapy remains elusive, there is compelling in vitro evidence that transplanted cells modulate the function of various immune cell types via release of paracrine factors, such as extracellular vesicles, although in vivo evidence is still limited. Investigation of the new paradigms reviewed herein should be a top priority because it may profoundly transform cell therapy and finally make it a reality.
Human cardiac stem cells Bearzi, Claudia; Rota, Marcello; Hosoda, Toru ...
Proceedings of the National Academy of Sciences - PNAS,
08/2007, Letnik:
104, Številka:
35
Journal Article
Recenzirano
Odprti dostop
The identification of cardiac progenitor cells in mammals raises the possibility that the human heart contains a population of stem cells capable of generating cardiomyocytes and coronary vessels. ...The characterization of human cardiac stem cells (hCSCs) would have important clinical implications for the management of the failing heart. We have established the conditions for the isolation and expansion of c-kit-positive hCSCs from small samples of myocardium. Additionally, we have tested whether these cells have the ability to form functionally competent human myocardium after infarction in immunocompromised animals. Here, we report the identification in vitro of a class of human c-kit-positive cardiac cells that possess the fundamental properties of stem cells: they are self-renewing, clonogenic, and multipotent. hCSCs differentiate predominantly into cardiomyocytes and, to a lesser extent, into smooth muscle cells and endothelial cells. When locally injected in the infarcted myocardium of immunodeficient mice and immunosuppressed rats, hCSCs generate a chimeric heart, which contains human myocardium composed of myocytes, coronary resistance arterioles, and capillaries. The human myocardium is structurally and functionally integrated with the rodent myocardium and contributes to the performance of the infarcted heart. Differentiated human cardiac cells possess only one set of human sex chromosomes excluding cell fusion. The lack of cell fusion was confirmed by the Cre-lox strategy. Thus, hCSCs can be isolated and expanded in vitro for subsequent autologous regeneration of dead myocardium in patients affected by heart failure of ischemic and nonischemic origin.
Ab maturation as well as memory B and plasma cell differentiation occur primarily in the germinal centers (GCs). Systemic lupus erythematosus (SLE) may develop as a result of enhanced GC activity. ...Previous studies have shown that the dysregulated STAT3 pathway is linked to lupus pathogenesis. However, the exact role of STAT3 in regulating SLE disease progression has not been fully understood. In this study, we demonstrated that STAT3 signaling in B cells is essential for GC formation and maintenance as well as Ab response. Increased cell apoptosis and downregulated Bcl-xL and Mcl-1 antiapoptotic gene expression were found in STAT3-deficient GC B cells. The follicular helper T cell response positively correlated with GC B cells and was significantly decreased in immunized B cell STAT3-deficient mice. STAT3 deficiency also led to the defect of plasma cell differentiation. Furthermore, STAT3 deficiency in autoreactive B cells resulted in decreased autoantibody production. Results obtained from B cell STAT3-deficient B6.MRL/lpr mice suggest that STAT3 signaling significantly contributes to SLE pathogenesis by regulation of GC reactivity, autoantibody production, and kidney pathology. Our findings provide new insights into the role of STAT3 signaling in the maintenance of GC formation and GC B cell differentiation and identify STAT3 as a novel target for treatment of SLE.
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