Analysis of the human intestinal epithelial cell transcriptional response to Lactobacillus acidophilus, Lactobacillus salivarius, Bifidobacterium lactis and Escherichia coli

The complex microbial population residing in the human gastrointestinal tract consists of commensal, potential pathogenic and beneficial species, which are probably perceived differently by the host and consequently could be expected to trigger specific transcriptional responses. Here, we provide a comparative analysis of the global in vitro transcriptional response of human intestinal epithelial cells to Lactobacillus acidophilus NCFM™, Lactobacillus salivarius Ls-33, Bifidobacterium animalis subsp. lactis 420, and enterohaemorrhagic Escherichia coli O157:H7 (EHEC). Interestingly, L. salivarius Ls-33 DCE-induced changes were overall more similar to those of B. lactis 420 than to L. acidophilus NCFM™, which is consistent with previously observed in vivo immunomodulation properties. In the gene ontology and pathway analyses both specific and unspecific changes were observed. Common to all was the regulation of apoptosis and adipogenesis, and lipid-metabolism related regulation by the probiotics. Specific changes such as regulation of cell-cell adhesion by B. lactis 420, superoxide metabolism by L. salivarius Ls-33, and regulation of MAPK pathway by L. acidophilus NCFM™ were noted. Furthermore, fundamental differences were observed between the pathogenic and probiotic treatments in the Toll-like receptor pathway, especially for adapter molecules with a lowered level of transcriptional activation of MyD88, TRIF, IRAK1 and TRAF6 by probiotics compared to EHEC. The results in this study provide insights into the relationship between probiotics and human intestinal epithelial cells, notably with regard to strain-specific responses, and highlight the differences between transcriptional responses to pathogenic and probiotic bacteria.

The murine nephrin gene is specifically expressed in kidney, brain and pancreas: inactivation of the gene leads to massive proteinuria and neonatal death

A mouse model for congenital nephrotic syndrome (NPHS1) was generated by inactivating the nephrin gene (Nphs1) in embryonic stem cells by homologous recombination. The targeting construct contained the Escherichia coli lacZ gene as a reporter for the Nphs1 promoter. Mice homozygous for inactivated Nphs1 were born at an expected frequency of 25%. Although seemingly normal at birth, they immediately developed massive proteinuria and edema and died within 24 h. The kidneys of null mice exhibited enlarged Bowman's spaces, dilated tubuli, effacement of podocyte foot processes and absence of the slit diaphragm, essentially as found in human NPHS1 patients. In addition to expression in glomerular podocytes, the reporter gene was expressed in the brain and pancreas of (+/-) and (-/-) mice. In the brain, expression was localized to the ventricular zone of the fourth ventricle, the developing spinal cord, cerebellum, hippocampus and olfactory bulb. In the cerebellum, the expression was seen in radial glial cells. Neither anatomical nor morphological abnormalities were observed in the brains of null mice.

Positionally cloned gene for a novel glomerular protein--nephrin--is mutated in congenital nephrotic syndrome

Congenital nephrotic syndrome of the Finnish type (NPHS1) is an autosomal-recessive disorder, characterized by massive proteinuria in utero and nephrosis at birth. In this study, the 150 kb critical region of NPHS1 was sequenced, revealing the presence of at least 11 genes, the structures of 5 of which were determined. Four different mutations segregating with the disease were found in one of the genes in NPHS1 patients. The NPHS1 gene product, termed nephrin, is a 1241-residue putative transmembrane protein of the immunoglobulin family of cell adhesion molecules, which by Northern and in situ hybridization was shown to be specifically expressed in renal glomeruli. The results demonstrate a crucial role for this protein in the development or function of the kidney filtration barrier.