Protein modifications, such as carbonylation, nitration and formation of lipid peroxidation adducts, e.g. 4-hydroxynonenal (HNE), are products of oxidative damage attributed to reactive oxygen species (ROS). The mitochondrial respiratory chain Complexes I and III have been shown to be a major source of ROS in vitro. Additionally, modifications of the respiratory chain Complexes (I-V) by nitration, carbonylation and HNE adduct decrease their enzymatic activity in vitro. However, modification of these respiratory chain complex proteins due to in vivo basal level ROS generation has not been investigated. In this study, we show a basal level of oxidative damage to specific proteins of adult bovine heart submitochondrial particle (SMP) complexes, and find that most of these proteins are localized in the mitochondrial matrix. We postulate that electron leakage from respiratory chain complexes and subsequent ROS formation may cause damage to specific complex subunits and contribute to long-term accumulation of mitochondrial dysfunction.

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For both men and women, ischemic heart disease is one of the leading causes of death in the United States today, and its pathobiology has been attributed to many factors, including proinflammatory cytokines. Interleukin (IL) 2 -18 is a pleiotropic cytokine belonging to the IL-1 family (1-5), whose expression is up-regulated in numerous immune, infectious, and inflammatory conditions (1-5), which may further amplify the inflammatory cascade by inducing additional cytokines, chemokines, and adhesion molecules (1-5). Elevated plasma IL-18 levels have been detected in patients with acute coronary syndromes (6), and a direct correlation between IL-18 levels and the severity of myocardial dysfunction has been reported. Circulating IL-18 levels have been shown to be independent predictors of coronary events in humans, with increased basal levels of IL-18 observed in individuals who later developed coronary events (7). Increased circulating IL-18 levels have also been measured during heart failure as well as in stroke patients (8, 9). IL-18 signals via the IL-18 receptor, a heterodimer consisting of a ligand binding ␣-subunit and a signal-transducing ␤-subunit (10, 11). Binding of IL-18 to IL-18R␣ recruits IL-18R␤, and this activated complex initiates pleiotropic signal transduction events. Similar to IL-1 receptor antagonist that blocks IL-1 signaling, IL-18-binding protein (IL-18BP) binds IL-18 with high affinity, inhibits IL-18 bioavailability (12), neutralizes IL-18 effects, and thus reduces inflammation. Interestingly, transgenic mice overexpressing human IL-18BP exhibit reduced inflammation and disease severity (13).Cytotoxic free radicals and proinflammatory cytokines are produced during ischemia/reperfusion (I/R) injury. Using isolated adult rat cardiomyocytes, we have recently described NF-B-dependent IL-18 and IL-18R␤ expression following hydrogen peroxide and TNF-␣ treatment in vitro (14). Moreover, although IL-18BP gene expression under basal conditions in these cells is undetectable, TNF-␣ and H 2 O 2 each induce IL-18BP mRNA in a delayed but persistent manner (14), which suggests tight regulation of IL-18 bioavailability. However, the precise role of IL-18 in I/R injury and its regulation in vivo are incompletely understood, and the signal transduction path-* This work was supported in part by the Research Service of the Department of Veterans Affairs. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Mitochondrial dysfunction generates reactive oxygen species (ROS) which damage essential macromolecules. Oxidative modification of proteins, DNA, and lipids has been implicated as a major causal factor in the age-associated decline in tissue function. Mitochondrial electron transport chain complexes I and III are the principle sites of ROS production, and oxidative modifications to the complex subunits inhibit their in vitro activity. Therefore, we hypothesize that mitochondrial complex subunits may be primary targets for oxidative damage by ROS which may impair normal complex activity by altering their structure/function leading to mitochondrial dysfunction associated with aging. This study of kidney mitochondria from young, middle-aged and old mice reveals that there are functional decreases in Complexes I, II, IV and V between aged compared to young kidney mitochondria and these functional declines directly correlate with increased oxidative modification to particular complex subunits. We postulate that the electron leakage from complexes causes specific damage to their subunits and increased ROS generation as oxidative damage accumulates, leading to further mitochondrial dysfunction, a cyclical process that underlies the progressive decline in physiologic function seen in aged mouse kidney. In conclusion, increasing mitochondrial dysfunction may play a key role in the age-associated decline in tissue function.

Interleukin (IL)-18 is a cardiotropic proinflammatory cytokine chronically elevated in the serum of patients with cardiac hypertrophy (LVH). The purpose of this study was to examine the role of IL-18 in pressure-overload hypertrophy using wild type (WT) and IL-18 −/− (null) mice. Adult male C57Bl/ 6 mice underwent transaortic constriction (TAC) for 7 days or sham surgery. Heart weight/body weight ratios showed blunted hypertrophy in IL-18 null TAC mice compared to WT TAC animals. Microarray analyses indicated differential expression of hypertrophy-related genes in WT versus IL-18 nulls. Northern, Western, and EMSA analyses showed Akt and GATA4 were increased in WT but unchanged in IL-18 null mice. Our results demonstrate blunted hypertrophy with reduced expression of contractile-, hypertrophy-, and remodeling-associated genes following pressure overload in IL-18 null mice, and suggest that IL-18 plays a critical role in the hypertrophic response.

Recent landmark molecular genetic studies have identified an evolutionarily conserved insulin/IGF-1 signal transduction pathway that regulates lifespan. In C. elegans, Drosophila, and rodents, attenuated insulin/IGF-1 signaling appears to regulate lifespan and enhance resistance to environmental stress. The Ames (Prop1 (df/df)) and Snell (Pit1 (dw/dw)) hypopituitary dwarf mice with growth hormone (GH), thyroid-stimulating hormone (TSH), and prolactin deficiencies live 40-60% longer than control mice. Both mutants are resistant to multiple forms of environmental stress in vitro. Taken collectively, these genetic models indicate that diminished insulin/IGF-l signaling may play a central role in the determination of mammalian lifespan by conferring resistance to exogenous and endogenous stressors. These pleiotropic endocrine pathways control diverse programs of gene expression that appear to orchestrate the development of a biological phenotype that promotes longevity. With the ability to investigate thousands of genes simultaneously, several microarray surveys have identified potential longevity assurance genes and provided information on the mechanism(s) by which the dwarf genotypes (dw/dw) and (df/df), and caloric restriction may lead to longevity. We propose that a comparison of specific changes in gene expression shared between Snell and Ames dwarf mice may provide a deeper understanding of the transcriptional mechanisms of longevity determination. Furthermore, we propose that a comparison of the physiological consequences of the Pit1dw and Prop1df mutations may reveal transcriptional profiles similar to those reported for the C. elegans and Drosophila mutants. In this study we have identified classes of genes whose expression is similarly affected in both Snell and Ames dwarf mice. Our comparative microarray data suggest that specific detoxification enzymes of the P(450) (CYP) family as well as oxidative and steroid metabolism may play a key role in longevity assurance of the Snell and Ames dwarf mouse mutants. We propose that the altered expression of these genes defines a biochemical phenotype which may promote longevity in Snell and Ames dwarf mice.

SummarySeveral murine models demonstrate that mammalian longevity can be increased by single gene mutations affecting endocrine signalling, particularly via the GH/IGF-1 axis. In this study, we identify age-independent patterns of hepatic gene expression characteristic of long-lived Snell ( Pit1