Alterations in proteoglycan synthesis selectively impair FSH-induced particulate cAMP-phosphodiesterase 4 (PDE4) activation in immature rat Sertoli cells

The mechanism of chronic unpredictable mild stress induced high blood pressure in rats: a proteomic and targeted metabolomic analysis

Chronic stress, a leading factor for high blood pressure (BP) and even hypertension, affects health quality seriously. However, the management is rather difficult in our rapidly developing modern society, and the underlying mechanism that caused hypertension remains incompletely understood. In this study, we established a rat model of high BP induced by chronic unpredictable mild stress (CUMS). The results showed that CUMS increased the BP and heart rate, as well as the concentrations of CORT, NA, and ACTH. Based on tandem mass tag (TMT)-labeled proteomics, 13 proteins changed in RVLM. Then, targeted metabolomics together with real-time qPCR were applied to validate the levels of the biomolecules quantitatively. The related molecules were confirmed to reveal that CUMS has a great role in the upregulation of muscle contraction, synthesis of cAMP and transport of metals, while down-regulating ralaxin signaling. This finding facilitates a better understanding of the mechanism of hypertension induced by chronic stress and could provide an insight into the prevention and treatment of hypertension.

Syndecan 1 represses cell growth and FSH responsiveness in human granulosa cells

Albeit devoid of intrinsic catalytic activity, the transmembrane heparan sulphate proteoglycan syndecan 1 plays critical roles in cellular processes such as extracellular matrix crosstalk, cytoskeletal organization, cell spreading, proliferation and differentiation. During the ovarian cycle, the expression of syndecan 1 in granulosa cells shows cyclic variation suggesting that it might fulfil specific roles in follicle development. To investigate its physiological roles on granulosa cells, syndecan 1 was overexpressed in human granulosa cell line KGN which retains features of granulosa cells from small antral follicle such as estradiol (E2) synthesis and low expression of functional FSH receptor (FSHR). We demonstrated that overexpression of syndecan 1 in immature granulosa cells (KGN-SDC1) induces a profound alteration in their intrinsic characteristics including enhanced spreading and attachment, both associated with a reduced growth rate. Flow cytometry analysis revealed that syndecan 1 overexpression increases the percentage of KGN cells in quiescent phase. This partial cell cycle exit is concordant with downregulated levels of CCND1 and CDK4 and upregulated expression of CDK inhibitor CDKN1A. In parallel both unstimulated and FSH-induced E2 synthesis are reduced in KGN-SDC1 through both repression of CYP19A1 and FSHR mRNA associated with decreased levels of potential regulators NR5A1 and ESR2. Additionally, we provide evidence that transient cAMP accumulation reduction in cells overexpressing syndecan 1 is accompanied by an increase in cAMP-hydrolysing PDE activity. Our results demonstrated that syndecan 1 might regulate differentiation of granulosa cells and follicular development by means of various mechanisms involving morphological changes, control of signalling pathways and alterations in gene expressions.

Free French abstract: A French translation of this abstract is freely available at http://www.reproduction-online.org/content/153/6/797/suppl/DC2

Alteration of cell membrane proteoglycans impairs FSH receptor/Gs coupling and ERK activation through PP2A-dependent mechanisms in immature rat Sertoli cells

BACKGROUND

During the pre-pubertal life, the cessation of Sertoli cell proliferation and the onset of differentiation are associated with a shift in the FSH-mediated signaling leading to inhibition of the ERK-mitogenic pathway and to a concomitant sensitization of cAMP/PKA pathway.

METHODS

To highlight the role of cell proteoglycans (PGs) in the shift of FSH signaling, both FSH-induced cAMP production and ERK1/2 inactivation were studied in untreated and sodium chlorate PG-depleted cultured Sertoli cells from 20day-old rats.

RESULTS

Depletion of cell membrane PGs by sodium chlorate reduced FSH-, but not cholera toxin-stimulated cAMP production as well as basal ERK phosphorylation through an okadaic acid (OA)-sensitive mechanism. Involvement of PP2A was further substantiated by a marked decrease in membrane- associated PP2A activity under SC conditions and by the OA-induced restoration of PKA-dependent ERK inactivation in SC-treated cells.

CONCLUSIONS

In 20-day-old rat Sertoli cells, transmembrane cell PGs, through tethering/activation of PP2A activity exerts regulatory control on both FSH receptor/Gs coupling and ERK phosphorylation.

GENERAL SIGNIFICANCE

Besides their antiproliferative roles, cell PGs such as syndecan-1, could be involved in the increase in cAMP response to FSH occurring in Sertoli cells at the time of transition between proliferative and differentiated states.

Increased particulate phosphodiesterase 4 in the prefrontal cortex supports 5-HT4 receptor-induced improvement of object recognition memory in the rat

RATIONALE

Serotonin receptors (5-HT4Rs) are critical to both short-term and long-term memory processes. These receptors mainly trigger the cyclic adenosine monophosphate (cAMP)/protein kinase A signaling pathway, which is regulated by cAMP phosphodiesterases (PDEs).

OBJECTIVES

We investigated the mechanisms underlying the effect of the selective activation of 5-HT4R on information acquisition in an object recognition memory task and the putative regulation of PDE.

MATERIALS AND METHODS

The effect of RS 67333 (1 mg/kg, intraperitoneally [i.p.], injected 30 min before the sample phase) was examined at different delay intervals in an object recognition task in Sprague-Dawley rats. After the testing trial, PDE activity of brain regions implicated in this task was assayed.

RESULTS

RS 67333-treated rats spent more time exploring the novel object after a 15-min (P < 0.001) or 4-h delay (P < 0.01) but not after a 24-h delay, whereas control animals showed no preference for the novel object for delays greater than 15 min. We characterized the specific patterns and kinetic properties of PDE in the prefrontal and perirhinal cortices as well as in the hippocampus. We demonstrated that particulate PDE activities increase in both the prefrontal cortex and hippocampus following 5-HT4R stimulation. In the prefrontal cortex, PDE4 activities support the RS 67333-induced modification of PDE activities, whereas in the hippocampus, all cAMP-PDE activities varied. In contrast, particulate PDE variation in the hippocampus was not found to support improvement of recognition memory after a 4-h delay.

CONCLUSIONS

We provide evidence that the increase in particulate PDE4 activity in the prefrontal cortex supports the 5-HT4R-induced increase in information acquisition.