Jean-François Chassé

The neuronal SAPK/JNK pathway is altered in a murine model of hyperhomocysteinemia

Deficiency in cystathionine beta synthase (CBS) leads to high plasma homocysteine concentrations and causes hyperhomocysteinemia, a common risk factor for vascular disease, stroke and possibly neurodegenerative diseases. Various neuronal diseases have been associated with hyperhomocysteinemia, but the molecular mechanisms of homocysteine toxicity are unknown. We investigated the pathways involved in the pathological process, by analyzing differential gene expression in neuronal tissues. We used a combination of differential display and cDNA arrays to identify genes differentially expressed during hyperhomocysteinemia in brain of CBS‐deficient mice. In this murine model of hyperhomocysteinemia, both plasma and brain homocysteine concentrations were high. Several genes were found to be differentially expressed in the brains of CBS‐deficient mice, and the identities of some of these genes suggested that the SAPK/JNK pathway was altered in the brains of CBS‐deficient mice. We therefore investigated the activation of proteins involved in the SAPK/JNK cascade. JNK and c‐Jun were activated in the hippocampal neurones of CBS‐deficient mice, suggesting that the SAPK/JNK pathway may play an important role in the development of neuronal defects associated with hyperhomocysteinemia.

Urinary Retinol Binding Protein Is a Marker of the Extent of Interstitial Kidney Fibrosis

Currently, a non-invasive method to estimate the degree of interstitial fibrosis (IF) in chronic kidney disease is not available in routine. The aim of our study was to evaluate the diagnostic performance of the measurement of urinary low molecular weight (LMW) protein concentrations as a method to determine the extent of IF. The urines specimen from 162 consecutive patients who underwent renal biopsy were used in the analysis. Numerical quantification software based on the colorimetric analysis of fibrous areas was used to assess the percentage IF. Total proteinuria, albuminuria, and the urinary levels of retinol binding protein (RBP), alpha1-microglobulin (α1MG), beta 2-microglobulin (β2MG), transferrin, and IgG immunoglobulins were measured. There was a significant correlation between the degree of IF and the RBP/creatinine (creat) ratio (R2: 0.11, p<0.0001). IF was associated to a lesser extent with urinary β2MG and α1MG; however, there was no association with total proteinuria or high molecular weight (HMW) proteinuria. The correlation between IF and RBP/creat remained significant after adjustment to the estimated glomerular filtration rate, age, body mass index, α1MG, and β2MG. The specificity of the test for diagnosing a fibrosis score of >25% of the parenchyma was 95% when using a threshold of 20 mg/g creat. In conclusion, RBP appears to be a quantitative and non-invasive marker for the independent prediction of the extent of kidney IF. Because methods for the measurement of urinary RBP are available in most clinical chemistry departments, RBP measurement is appealing for implementation in the routine care of patients with chronic kidney disease.

Identification of a new stilbene-derived inducer of paraoxonase 1 and ligand of the Aryl hydrocarbon Receptor.

Paraoxonase 1 (PON1) is a high-density lipoprotein-associated enzyme, synthesized in the liver and secreted into the blood. PON1 displays antioxidant properties and is involved in organophosphorous compounds and oxidized lipids degradation. Because of these beneficial effects, pharmacological regulation of PON1 appears to be highly relevant in toxicology and cardiology. Recent studies undertaken on the regulation of the PON1 promoter in our laboratory have identified resveratrol, through its activation of the Aryl hydrocarbon Receptor (AhR), as a putative inducer of PON1. We have tested a new modulator of AhR, (Z)-2,3-bis (4-nitrophenyl)-acrylonitrile, and established that it is a more potent inducer of PON1 at the mRNA, protein and enzymatic activity as compared to resveratrol. It also acts by activating the AhR. However, in contrast with traditional AhR agonists, it does not induce cyp1A1 transcription. (Z)-2,3-bis (4-nitrophenyl)-acrylonitrile is therefore a specific AhR modulator targeting PON1.

Pegylated liposomal doxorubicin (Caelyx®) interference with the spectrophotometric Jaffe method for quantitative determination of creatinine in human plasma.

• We investigated the in vitro and in vivo pegylated liposomal doxorubicin interference on plasma creatinine determination.

Intérêt du dosage des protéines spécifiques urinaires dans le diagnostic des pathologies rénales

The analysis of urinary protein composition is an important step in the evaluation and monitoring of kidney diseases. Among the various approaches, the determination of urinary-specific proteins makes it possible to non-invasively detect a preferentially tubular or glomerular injury, to orientate towards a pathological process, to guide the indication of a kidney biopsy, and to follow the evolution of the disease and the effectiveness of a therapy. No study systematically evaluated the performance of urinary-specific proteins for the diagnosis of a renal disease. We conducted this retrospective study to perform an exhaustive analysis of the correlations that may exist between histologically proven kidney disease and the corresponding specific urinary protein composition it in order to evaluate the diagnostic value of each of its components. Urinary concentrations of total protein, albumin, transferrin, alpha1microglobulin, beta2microglobulin, retinol binding protein, and immunoglobulin G were analyzed in more than 500 patients who underwent renal biopsy and concomitant urine specific protein analysis. Our analysis shows that these markers have a limited positive predictive value in this cohort of complex and unselected kidney diseases. In particular, low molecular weight proteins, and especially alpha1microglobulin, are frequently associated with glomerular diseases. We identified transferrin as an independent predictor of minimal changes disese and renal amyloidosis, and beta2microglobulin as an independent predictor of acute tubulointerstitial nephropathy and myelomatous tubulopathy. Finally, we defined the thresholds at which these parameters had excellent negative predictive values.

Characterisation of a human liver cystathionine beta synthase mRNA sequence corresponding to the c.[833T>C;844_845ins68] mutation in CBS gene.

Cystathionine beta synthase (CBS) is the only reaction that removes homocysteine from methionine cycle and redirects it to the transsulfuration pathway. The c.[833T>C;844_845ins68] mutation in the CBS gene has been reported initially as corresponding to classic homocystinuria. Studies showing that the insertion is associated with very smalls amounts of the transcript in the nucleus; others suggest that the heterozygous and homozygous subjects are protected against hyperhomocysteinemia and that the insertion tends to rescue the protein function. The liver is the major organ which metabolizes the circulating homocysteine to cystathionine. We have determined the sequence of the liver mRNA corresponding to the CBS c.[833T>C;844_845ins68] gene. We have shown that a novel splicing event could account for the modification in protein and possibly in enzyme activity.