Fluorogenic tagging of protein 3-nitrotyrosine with 4-(aminomethyl)benzene sulfonate in tissues: a useful alternative to Immunohistochemistry for fluorescence microscopy imaging of protein nitration

Protein tyrosine nitration is a common biomarker of biological aging and diverse pathologies associated with the excessive formation of reactive oxygen and nitrogen species. Recently, we suggested a novel fluorogenic derivatization procedure for the detection of 3-nitrotyrosine (3-NT) using benzylamine derivatives to convert specifically protein- or peptide-bound 3-NT to a highly fluorescent benzoxazole product. In this study, we applied this procedure to fluorogenic derivatization of protein 3-NT in sections from adult rat cerebellum to: (i) test this method for imaging nitrated proteins in fixed brain tissue sections and (ii) compare the chemical approach to immunohistochemical labeling with anti-3-NT antibodies. Immunofluorescence analysis of cerebellar sections using anti-3-NT antibodies showed differential levels of immunostaining in the molecular, Purkinje, and granule cell layers of the cerebellar cortex; in agreement with previous reports, the Purkinje cells were most highly labeled. Importantly, fluorogenic derivatization reactions of cerebellar proteins with 4-(aminomethyl)benzene sulfonic acid (ABS) and K(3)Fe(CN)(6) at pH 9, after sodium dithionite reduction of 3-NT to 3-aminotyrosine, showed a very similar pattern of relative intensity of cell labeling and improved resolution compared with antibody labeling. Our data demonstrate that ABS derivatization may be either a useful alternative to or a complementary approach to immunolabeling in imaging protein nitration in cells and tissues, including under conditions of dual labeling with antibodies to cell proteins, thus allowing for cellular colocalization of nitrated proteins and any protein of interest.

Nitration and inactivation of tyrosine hydroxylase by peroxynitrite

Tyrosine hydroxylase (TH) is modified by nitration after exposure of mice to 1-methyl-4-phenyl-1,2,3,6-tetrahydrophenylpyridine. The temporal association of tyrosine nitration with inactivation of TH activity in vitro suggests that this covalent post-translational modification is responsible for the in vivo loss of TH function (Ara, J., Przedborski, S., Naini, A. B., Jackson-Lewis, V., Trifiletti, R. R., Horwitz, J., and Ischiropoulos, H. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 7659-7663). Recent data showed that cysteine oxidation rather than tyrosine nitration is responsible for TH inactivation after peroxynitrite exposure in vitro (Kuhn, D. M., Aretha, C. W., and Geddes, T. J. (1999) J. Neurosci. 19, 10289-10294). However, re-examination of the reaction of peroxynitrite with purified TH failed to produce cysteine oxidation but resulted in a concentration-dependent increase in tyrosine nitration and inactivation. Cysteine oxidation is only observed after partial unfolding of the protein. Tyrosine residue 423 and to lesser extent tyrosine residues 428 and 432 are modified by nitration. Mutation of Tyr(423) to Phe resulted in decreased nitration as compared with wild type protein without loss of activity. Stopped-flow experiments reveal a second order rate constant of (3.8 +/- 0.9) x 10(3) m(-1) s(-1) at pH 7.4 and 25 degrees C for the reaction of peroxynitrite with TH. Collectively, the data indicate that peroxynitrite reacts with the metal center of the protein and results primarily in the nitration of tyrosine residue 423, which is responsible for the inactivation of TH.

Identification of tumor markers in models of human colorectal cancer using a 19,200-element complementary DNA microarray

Metastasis represents a crucial transition in disease development and progression and has a profound impact on survival for a wide variety of cancers. Cell line models of metastasis have played an important role in developing our understanding of the metastatic process. We used a 19,200-element human cDNA microarray to profile transcription in three paired cell-line models of colorectal tumor metastasis. By correlating expression patterns across these cell lines, we have identified 176 genes that appear to be differentially expressed (greater than 2-fold) in all highly metastatic cell lines relative to their reference. An analysis of these genes reiterates much of our understanding of the metastatic process and suggests additional genes, many of previously uncharacterized function, that may be causatively involved in, or at least prognostic of, metastasis. Northern analysis of a limited number of these genes validates the observed pattern of expression and suggests that further investigation and functional characterization of the identified genes is warranted.

Gene expression analysis of the Streptococcus pneumoniae competence regulons by use of DNA microarrays

Competence for genetic transformation in Streptococcus pneumoniae is coordinated by the competence-stimulating peptide (CSP), which induces a sudden and transient appearance of competence during exponential growth in vitro. Models of this quorum-sensing mechanism have proposed sequential expression of several regulatory genes followed by induction of target genes encoding DNA-processing-pathway proteins. Although many genes required for transformation are known to be expressed only in response to CSP, the relative timing of their expression has not been established. Overlapping expression patterns for the genes cinA and comD (G. Alloing, B. Martin, C. Granadel, and J. P. Claverys, Mol. Microbiol. 29:75-83, 1998) suggest that at least two distinct regulatory mechanisms may underlie the competence cycle. DNA microarrays were used to estimate mRNA levels for all known competence operons during induction of competence by CSP. The known competence regulatory operons, comAB, comCDE, and comX, exhibited a low or zero initial (uninduced) signal, strongly increased expression during the period between 5 and 12 min after CSP addition, and a decrease nearly to original values by 15 min after initiation of exposure to CSP. The remaining competence genes displayed a similar expression pattern, but with an additional delay of approximately 5 min. In a mutant defective in ComX, which may act as an alternate sigma factor to allow expression of the target competence genes, the same regulatory genes were induced, but the other competence genes were not. Finally, examination of the expression of 60 candidate sites not previously associated with competence identified eight additional loci that could be induced by CSP.

Alterations in protein synthesis induced by C2 toxin in 3T3 cells

We have studied the effect of actin skeleton depolymerisation induced by C2 toxin on protein synthesis in 3T3 cells. The toxin that was purified from culture medium of Clostridium botulinum type C was shown to specifically ADP-ribosylate actin in vitro and in vivo. Cells exposed to C2 toxin were rounded off, which was accompanied by disappearance of stress fibers. The rate of total protein synthesis decreased two-three times in the treated cells. This correlated with the reduction in amount of polyribosomes. The rates of specific protein synthesis were compared using 2D electrophoresis of pulse-labeled proteins. Dramatic changes were observed in the synthesis of a small group of cellular proteins. Our results indicate that actin filament depolymerization affects gene expression at the level of translation and/or through the control of mRNA concentrations.

The chemiluminescence assay of lipid peroxidation products in human blood plasma lipoproteins

A chemiluminescence (CL) flash kinetics on the addition of Fe2+ ions into oxidized low density lipoprotein (LDL) suspension has been studied. LDL oxidation was carried out at 37 degrees C without and in the presence of 5 or 50 microM of Cu2+. It has been found that under certain experimental conditions (the addition of excess iron ions, more than 1 mM) the amplitude of CL flash depended almost linearly (1) on the concentration of oxidized LDL and (2) on the extent of LDL oxidation measured as diene conjugates (DC) and 2-thiobarbituric acid-reactive substance (TBARS) accumulation. The corresponding correlation coefficients were: for TBARS -0.94 and for DC -0.97, in the case of LDL autooxidation; 0.72 and 0.98, in the case of copper-induced LDL oxidation. A sensitivity of the CL method was shown to be significantly enhanced (by more than two orders) in the presence of CL sensitizer--2,3,5,6-1H,4H-tetrahydro-9-(2'-benzoimidazolyl)-qui nolizin-(9,9a,1- gh)coumarin.

Mitochondrial abnormalities in myocardium of dogs with chronic heart failure

The number, size and structural integrity of mitochondria (MIT) were evaluated in the myocardium of 12 dogs with chronic heart failure (CHF) produced by sequential intracoronary microembolizations (EMB). Tissue specimens for transmission electron microscopy were obtained from the left ventricular (LV) free wall, septum and right ventricular free wall 3 to 4 months after the last EMB. Comparisons were made with samples obtained from identical sites in 9 control dogs. In dogs with CHF, LV ejection fraction decreased from 61 +/- 1% at baseline (prior to EMB) to 22 +/- 2% 3 to 4 months after the last EMB (P < 0.01) while plasma norepinephrine (PNE) concentration increased from 364 +/- 12 pg/ml to 837 +/- 150 pg/ml (P < 0.01). The number of MIT in an area of 100 square sarcomeres was greater in CHF dogs compared to controls (92 +/- 5 vs 64 +/- 2) (P < 0.001); whereas the average size of MIT was smaller (0.53 +/- 0.03 vs. 0.78 +/- 0.04 microm2) (P < 0.001). Injury ranging in severity from matrix depletion to myelinization and membrane disruption was present in 27 +/- 4% of MIT of CHF dogs compared to only 3 +/- 1% of MIT of controls (P < 0.001). MIT abnormalities were present to the same extent in all three regions of the heart. The severity of MIT injury, assessed on the basis of an injury index, was significantly higher in CHF dogs with PNE > or = 600 pg/ml (0.64 +/- 0.07) compared to CHF dogs with PNE < 600 pg/ml (0.32 +/- 0.08) (P < 0.01). Among CHF dogs, the MIT injury index was linearly related to PNE concentration (r = 0.57, P < 0.05), LV ejection fraction (r = 0.57, P < 0.05) and LV end-diastolic pressure (r = 0.57, P < 0.05). These data indicate that profound MIT abnormalities are present in the myocardium of dogs with CHF and are related to PNE concentration and to the severity of LV dysfunction.