Stimulation of KLF14/PLK1 pathway by thrombin signaling potentiates endothelial dysfunction in Type 2 diabetes mellitus.

Type 2 diabetes mellitus (T2DM) promotes a high oxidative stress and hypercoagulable state that drives microvascular injury and multiple-organ abnormality. Elevated thrombin activity underlies T2DM-linked endothelial dysfunction, but the mechanistic links between T2DM/oxidative stress axis and thrombin-associated endothelial pathologies are incompletely understood. In this work, immunohistochemical studies and quantitative analysis using isolated endothelial cells (ECs) identified accumulated Kru¨ppel-like family of transcription factor 14 (KLF14) deposits in ECs from multiple organs as distinct features of T2DM mice. KLF14 upregulation in ECs, which was stimulated by thrombin treatment, was dependent on multiple pathways including calcium mobilization, activation of PKC and AMPK pathways. Functionally, inhibition of endogenous KLF14 expression significantly attenuated thrombin-induced endotheliocyte proliferation, endothelial cell migration and oxidative stress. Molecularly, by directly binding the promoter, KLF14 functions as a transcriptional activator of PLK1, a polo-like kinase whose overexpression induced excessive reactive oxygen species (ROS) production. Transient knockdown of PLK1 was sufficient to suppress KLF14 overexpression-potentiated endothelial dysfunction. Collectively, these data provide proof of concept that deregulation of KLF14/PLK1 cascade plays a key role in thrombin-induced endothelial dysfunction and targeting KLF14 or PLK1 may limit thrombin-associated pathologies in T2DM patients.

Deregulation of WNT2/FZD3/ß-catenin pathway compromises the estrogen synthesis in cumulus cells from patients with polycystic ovary syndrome.

Mechanistic insight into estrogen deficiency by polycystic ovary syndrome (PCOS) remains a longstanding challenge in reproductive medicine. Recent advance suggest that Wingless-type MMTV integration site family members (WNTs), in concert with its Frizzled (FZD) receptors, regulate normal folliculogenesis, luteogenesis and ovarian steroidogenesis. However, no studies have so far investigated any causality between WNT-FZDs interactions and disrupted estrogen synthesis under certain pathological conditions. Here, we show that (i) FZD3 expression was significantly up-regulated in the cumulus cells (CCs) from PCOS patients. This up-regulation, along with the activation of WNT2/ß-Catenin pathway, was tightly associated with insulin resistance and estrogen deficiency, two hallmarks of PCOS. (ii) Overexpression of exogenous FZD3 in human granulosa cell COV434 impaired long-term FSH incubation-induced CYP19A1 transactivation and the recruitment of ß-Catenin onto CYP19A1 promoter, and subsequently compromised FSH-stimulated estrogen production. (iii) Conversely, inhibition of FZD3 expression exhibited a therapeutic effect on estrogen synthesis in PCOS CCs. Thus, excessive FZD3 expression in CCs may act as a brake on steroidogenic activation that is normally overcome by FSH stimulation. Future endeavor in this field should help to elucidate the complicated crosstalk between energy metabolism and endocrine cells through WNT/FZD signaling molecules.

Elicitation of metastasis associated protein 2 expression in the phagocytosis by murine testicular Sertoli cells.

Efficient phagocytic clearance of apoptotic spermatogenic cells and residual bodies (RBs) by Sertoli cells (SCs) is crucial for functional mature spermatogenesis. However, little is known about the molecular mechanisms underlying this SCs function. Herein, we reported for the first time that SCs-expressing metastasis associated protein 2 (Mta2), a chromatin modifier playing a critical role in modifying DNA accessibility for transcriptional regulation, was steadily up-regulated when SCs were co-cultured with RBs. The most efficient stimulatory substrates for the inducement of phagocytosis-elicited Mta2 expression were RBs and fragments from apoptotic spermatocytes. Furthermore, one major result of this response is the transcriptional repression of follicle-stimulating hormone receptor gene (Fshr) expression during phagocytosis, which should lead to a low level of circulated FSH because effects of FSH on spermatogenesis is fundamentally regulated by the down-regulation of Fshr after exposure to FSH. Given that high concentration of circulated FSH inhibits SCs phagocytic activity and impairment of MTA2 expression is associated with the abnormal high level of serum FSH, our present results suggest that the FSH/MTA2/Fshr cascade may serve as an indispensable negative feedback mechanism to help to maintain low level of circulated FSH, which is required for the normal occurrence of SCs phagocytosis.