Although nitrite reactions have been studied in the past, the specific reaction with collagen and its role in aging has never been examined. We have recently observed that in vitro nitrite-treated collagen shows similarities with aged human collagen. Shared properties include the formation of a unique tyrosine derivative we call compound N, a decease in unmodified tyrosine residues, the accumulation of a yellowish chromophore absorbing at 350 nm, and an increase in collagen cross-linking. Increased cross-linking, evidenced by a decreased susceptibility to enzymatic digestion, results in the stiffening of collagen and may account for the stiffening of human blood vessels, lung, and skin which occurs with aging. The majority of human exposure to nitrite results from endogenous nitric oxide production and exogenous sources which include cigarette smoking and cured meat ingestion. In order to establish the in vivo significance of the nitrite/collagen reaction to age-related changes in human collagen we will develop methods to detect biomarkers of the reaction (especially tyrosine derivatives such as compound N, 3-nitrotyrosine, dityrosine, diazotyrosine and deaminated diazotyrosine). Kinetics on the reactions between nitrite and potential reaction intermediates will be conduced in order to more precisely define the mechanism of reaction involved. The biomarkers and reaction intermediates will be identified by reverse phase HPLC amino acid analysis with photodiode array, fluorescence, and electrochemical in-line detection systems. The methods for biomarker detection will be used to compare collagen extracted from the skin, aorta, and lung of young and old individuals. Degree of cross-linking and tyrosine content will also be determined for each collagen sample. Statistical analyses will include multiple logistic regressions with age and smoking as independent variables. Finally, we will examine the effectiveness of free radical scavengers such as vitamins A, C and E to modulate these reactions in vitro. Because cigarette smoking is a major source of an individual's exogenous nitrite exposure, the nitrite/collagen reaction may provide important clues to the pathogenesis of disease processes associated with both aging and cigarette smoking. These include a variety of atherosclerotic vascular diseases, chronic obstructive pulmonary disease, premature sign wrinkling, and age-related lens cataracts.
|Maltsev, Victor A; Lakatta, Edward G (2007) Normal heart rhythm is initiated and regulated by an intracellular calcium clock within pacemaker cells. Heart Lung Circ 16:335-48|
|Jiang, Rui; Paik, David C; Hankinson, John L et al. (2007) Cured meat consumption, lung function, and chronic obstructive pulmonary disease among United States adults. Am J Respir Crit Care Med 175:798-804|
|Paik, David C; Saito, Lynne Y; Sugirtharaj, Dorcas D et al. (2006) Nitrite-induced cross-linking alters remodeling and mechanical properties of collagenous engineered tissues. Connect Tissue Res 47:163-76|
|Wang, Zhen; Paik, David C; Del Priore, Lucian V et al. (2005) Nitrite-modified extracellular matrix proteins deleteriously affect retinal pigment epithelial cell function and viability: a comparison study with nonenzymatic glycation mechanisms. Curr Eye Res 30:691-702|
|Paik, D C; Dillon, J; Galicia, E et al. (2001) The nitrite/collagen reaction: non-enzymatic nitration as a model system for age-related damage. Connect Tissue Res 42:111-22|
|Paik, D C; Saborio, D V; Oropeza, R et al. (2001) The epidemiological enigma of gastric cancer rates in the US: was grandmother's sausage the cause? Int J Epidemiol 30:181-2|