Publications

In various mammalian species, including humans, water restriction leads to an acute increase in urinary sodium excretion. This process, known as dehydration natriuresis, helps prevent further accentuation of hypernatremia and the accompanying rise in extracellular tonicity. Serum- and glucocorticoid-inducible kinase (Sgk1), which is expressed in the renal medulla, is regulated by extracellular tonicity. However, the mechanism of its regulation and the physiological role of hypertonicity-induced SGK1 gene expression remain unclear. Here, we identified a tonicity-responsive enhancer (TonE) upstream of the rat Sgk1 transcriptional start site. The transcription factor NFAT5 associated with TonE in a tonicity-dependent fashion in cultured rat renal medullary cells, and selective blockade of NFAT5 activity resulted in suppression of the osmotic induction of the Sgk1 promoter. In vivo, water restriction of rats or mice led to increased urine osmolality, increased Sgk1 expression, increased expression of the type A natriuretic peptide receptor (NPR-A), and dehydration natriuresis. In cultured rat renal medullary cells, siRNA-mediated Sgk1 knockdown blocked the osmotic induction of natriuretic peptide receptor 1 (Npr1) gene expression. Furthermore, Npr1-/- mice were resistant to dehydration natriuresis, which suggests that Sgk1-dependent activation of the NPR-A pathway may contribute to this response. Collectively, these findings define a specific mechanistic pathway for the osmotic regulation of Sgk1 gene expression and suggest that Sgk1 may play an important role in promoting the physiological response of the kidney to elevations in extracellular tonicity.

BACKGROUND

Although the MMP-2 promoter lacks a canonical progesterone response element (PRE), the hormone inhibits MMP-2 expression and is part of treatment protocols in gynecological invasive pathologies, including endometriosis and endometrial hyperplasia. This study aimed to explore the mechanism by which progesterone inhibits MMP-2 expression.

METHODS

The effect of progesterone on MMP-2 expression in the JAR human choriocarcinoma cell line was analyzed by gelatin zymography. MMP-2 transcript expression was studied using Northern blot and semi-quantitative RT-PCR. Rat promoter deletion analysis, electrophoretic mobility shift and chromatin immuno-precipitation assays were performed in order to locate the DNA binding site and the transcription factors involved in MMP-2 regulation.

RESULTS

Progesterone significantly decreased secretion of pro-MMP-2 and MMP-2 transcript expression level in a dose-dependent manner. Progesterone (1 microM) significantly decreased both human and rat MMP-2 promoter activity (80.1% +/- 0.3 and 81.3% +/- 0.23, respectively). Progesterone acts through the SP1 family transcription factors-binding site, located between -1433 and -1342 bp region from the transcriptional start site of the rat MMP-2 promoter, which are present in the orthologous human MMP-2 promoter. Progesterone receptor (PR), SP2, SP3 and SP4 proteins are constitutively bound to this consensus sequence.

CONCLUSION

Progesterone reduces PR and SP4 binding to the MMP-2 promoter, thereby suppressing transcription. Progesterone also promotes SP4 degradation. These novel mechanisms of MMP-2 regulation by progesterone provide the biological rationale for the use of progesterone in clinical settings associated with increased MMP-2 expression.

BACKGROUND

Human rhinoviruses (HRVs) characteristically cause upper respiratory tract infection, but they also infect the lower airways, causing acute bronchitis and exacerbating asthma.

OBJECTIVE

Our purpose was to study ex vivo the differences in the response to HRV infection of nasal and bronchial epithelial cultures from the same healthy and asthmatic individuals using conditions favoring development of fully differentiated, pseudostratified mucociliary epithelium.

METHODS

Cells from the inferior turbinates and bronchial tree of 5 healthy and 6 asthmatic individuals were cultured at an air-liquid interface. Cultures were infected with HRV-16, and after 48 hours, the degree of infection was measured.

RESULTS

Baseline median transepithelial resistance was lower in human bronchial epithelial (HBE) cell cultures than in human nasal epithelial (HNE) cell cultures (195 Omega.cm2 [95% CI, 164-252] vs 366 Omega.cm2 [95% CI, 234-408], respectively; P < .01). Virus replicated more easily in HBE cells than in HNE cells based on virus shedding in apical wash (log tissue culture infective dose of 50%/0.1 mL = 2.0 [95% CI, 1.0-2.5] vs 0.5 [95% CI, 0.5-1.5], P < .01) and on a 20- to 30-fold greater viral load and number of infected cells in HBE cell cultures than in HNE cell cultures. The increases in expression of RANTES and double-stranded RNA-dependent protein kinase were greater in HBE cell cultures than in HNE cell cultures, as were the concentrations of IL-8, IL-1alpha, RANTES, and IP-10 in basolateral medium. However, no significant differences between asthmatic and healthy subjects (including IFN-beta1 expression) were found.

CONCLUSIONS

Differentiated nasal epithelial cells might have mechanisms of increased resistance to rhinovirus infection compared with bronchial epithelial cells. We could not confirm previous reports of increased susceptibility to HRV infection in epithelial cells from asthmatic subjects.