Interleukin-6 induction of protein s is regulated through signal transducer and activator of transcription 3

Concurrent Targeting of Potential Cancer Stem Cells Regulating Pathways Sensitizes Lung Adenocarcinoma to Standard Chemotherapy

Cancer stem cells (CSC) are highly resistant to conventional chemotherapeutic drugs. YAP1 and STAT3 are the two transcription factors that facilitate the therapeutic resistance and expansion of CSCs. The objective of this study was to understand the cross-talk between YAP1 and STAT3 activities and to determine the therapeutic efficacy of targeting dual CSC-regulating pathways (YAP1 and STAT3) combined with chemotherapy in lung adenocarcinoma. Here, we showed that YAP1 contributes to CSC regulation and enhances tumor formation while suppressing apoptosis. Mechanistically, YAP1 promotes phosphorylation of STAT3 by upregulating IL6. In lung adenocarcinoma clinical specimens, YAP1 expression correlated with that of IL6 (P < 0.01). More importantly, YAP1 and phosphorylated STAT3 (pSTAT3) protein expressions were significantly correlated (P < 0.0001) in primary lung adenocarcinoma as determined by IHC. Immunoblotting of 13 lung adenocarcinoma patient-derived xenografts (PDX) showed that all YAP1-expressing PDXs also exhibited pSTAT3. Additional investigations revealed that chemotherapy resistance and malignant stemness were influenced by upregulating NANOG, OCT4, and SOX2, and the expression of these targets significantly attenuated by genetically and pharmacologically hindering the activities of YAP1 and STAT3 in vivo and in vitro Therapeutically, the dual inhibition of YAP1 and STAT3 elicits a long-lasting therapeutic response by limiting CSC expansion following chemotherapy in cell line xenograft and PDX models of lung adenocarcinoma. Collectively, these findings provide a conceptual framework to target the YAP1 and STAT3 pathways concurrently with systemic chemotherapy to improve the clinical management of lung adenocarcinoma, based on evidence that these two pathways expand CSC populations that mediate resistance to chemotherapy.

COVID-19: a probable role of the anticoagulant Protein S in managing COVID-19-associated coagulopathy

The COVID-19 pandemic has caused monumental mortality, and there are still no adequate therapies. Most severely ill COVID-19 patients manifest a hyperactivated immune response, instigated by interleukin 6 (IL6) that triggers a so called "cytokine storm" and coagulopathy. Hypoxia is also associated with COVID-19. So far overlooked is the fact that both IL6 and hypoxia depress the abundance of a key anticoagulant, Protein S. We speculate that the IL6-driven cytokine explosion plus hypoxemia causes a severe drop in Protein S level that exacerbates the thrombotic risk in COVID-19 patients. Here we highlight a mechanism by which the IL6-hypoxia curse causes a deadly hypercoagulable state in COVID-19 patients, and we suggest a path to therapy.

Protein S Protects against Podocyte Injury in Diabetic Nephropathy

Background Diabetic nephropathy (DN) is a leading cause of ESRD in the United States, but the molecular mechanisms mediating the early stages of DN are unclear.Methods To assess global changes that occur in early diabetic kidneys and to identify proteins potentially involved in pathogenic pathways in DN progression, we performed proteomic analysis of diabetic and nondiabetic rat glomeruli. Protein S (PS) among the highly upregulated proteins in the diabetic glomeruli. PS exerts multiple biologic effects through the Tyro3, Axl, and Mer (TAM) receptors. Because increased activation of Axl by the PS homolog Gas6 has been implicated in DN progression, we further examined the role of PS in DN.Results In human kidneys, glomerular PS expression was elevated in early DN but suppressed in advanced DN. However, plasma PS concentrations did not differ between patients with DN and healthy controls. A prominent increase of PS expression also colocalized with the expression of podocyte markers in early diabetic kidneys. In cultured podocytes, high-glucose treatment elevated PS expression, and PS knockdown further enhanced the high-glucose-induced apoptosis. Conversely, PS overexpression in cultured podocytes dampened the high-glucose- and TNF-α-induced expression of proinflammatory mediators. Tyro3 receptor was upregulated in response to high glucose and mediated the anti-inflammatory response of PS. Podocyte-specific PS loss resulted in accelerated DN in streptozotocin-induced diabetic mice, whereas the transient induction of PS expression in glomerular cells in vivo attenuated albuminuria and podocyte loss in diabetic OVE26 mice.Conclusions Our results support a protective role of PS against glomerular injury in DN progression.

Associations between pre-eclampsia and protein C and protein S levels among pregnant Nigerian women

OBJECTIVE

To evaluate levels of protein C and free protein S among women with pre-eclampsia, and determine whether there is a relationship between deficiencies and pre-eclampsia.

METHODS

A cross-sectional study was conducted at a hospital in Nigeria from July 2013 to March 2014 among 90 pregnant women with pre-eclampsia (blood pressure ≥140/90 mm Hg, proteinuria ≥300 mg in 24 hours) and 90 normotensive pregnant women (control group). Plasma levels of protein C and free protein S were analyzed by enzyme-linked immunosorbent assay, and protein C activity by a chromogenic method.

RESULTS

Mean protein C antigen and activity levels did not differ between groups (P=0.639 and P=0.444, respectively). The incidence of protein C antigen and activity deficiency also did not differ (P=0.288 and P>0.99, respectively). The mean free protein S antigen level was higher among women with pre-eclampsia (54.48%±19.58%) than in the control group (47.23%±10.27%; P=0.004). No woman in the control group had protein S deficiency, as compared with 2 (2%) of the women with pre-eclampsia (P=0.497). No association was found between deficiencies of these proteins and pre-eclampsia.

CONCLUSION

Deficiencies of protein C and free protein S are unlikely to be etiopathogenetic for pre-eclampsia; therefore, therapeutic intervention should focus on other potential pathogenetic pathways.

Interleukin-6 inhibition of peroxisome proliferator-activated receptor alpha expression is mediated by JAK2- and PI3K-induced STAT1/3 in HepG2 hepatocyte cells

Interleukin-6 (IL-6) is the major activator of the acute phase response (APR). One important regulator of IL-6-activated APR is peroxisome proliferator-activated receptor alpha (PPARα). Currently, there is a growing interest in determining the role of PPARα in regulating APR; however, studies on the molecular mechanisms and signaling pathways implicated in mediating the effects of IL-6 on the expression of PPARα are limited. We previously revealed that IL-6 inhibits PPARα gene expression through CAAT/enhancer-binding protein transcription factors in hepatocytes. In this study, we determined that STAT1/3 was the direct downstream molecules that mediated the Janus kinase 2 (JAK2) and phosphatidylinositol-3 kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathways in IL-6-induced repression of PPARα. Treatment of cells with pharmacological inhibitors of JAK2, PI3K, AKT, and mTOR attenuated the inhibitory effect of IL-6 on PPARα protein in a dose-dependent manner. These inhibitors also decreased the IL-6-induced repression of PPARα mRNA expression and promoter activity. Overexpression of STAT1 and STAT3 in HepG2 cells cotransfected with a reporter vector containing this PPARα promoter region revealed that both the expression plasmids inhibited the IL-6-induced repression of PPARα promoter activity. In the presence of inhibitors of JAK2 and mTOR (AG490 and rapamycin, respectively), IL-6-regulated protein expression and DNA binding of STAT1 and STAT3 were either completely or partially inhibited simultaneously, and the IL-6-induced repression of PPARα protein and mRNA was also inhibited. This study has unraveled novel pathways by which IL-6 inhibits PPARα gene transcription, involving the modulation of JAK2/STAT1-3 and PI3K/AKT/mTOR by inducing the binding of STAT1 and STAT3 to STAT-binding sites on the PPARα promoter. Together, these findings represent a new model of IL-6-induced suppression of PPARα expression by inducing STAT1 and STAT3 phosphorylation and subsequent down-regulation of PPARα mRNA expression.

LPS-Toll-Like Receptor-Mediated Signaling on Expression of Protein S and C4b-Binding Protein in the Liver

Protein S (PS), mainly synthesized in hepatocytes and endothelial cells, plays a critical role as a cofactor of anticoagulant activated protein C (APC). PS activity is regulated by C4b-binding protein (C4BP), structurally composed of seven α-chains (C4BPα) and a β-chain (C4BPβ). In this paper, based primarily on our previous studies, we review the lipopolysaccharide (LPS)-induced signaling which affects expression of PS and C4BP in the liver. Our in vivo studies in rats showed that after LPS injection, plasma PS levels are significantly decreased, whereas plasma C4BP levels first are transiently decreased after 2 to 12 hours and then significantly increased after 24 hours. LPS decreases PS antigen and mRNA levels in both hepatocytes and sinusoidal endothelial cells (SECs), and decreases C4BP antigen and both C4BPα and C4BPβ mRNA levels in hepatocytes. Antirat CD14 and antirat Toll-like receptor (TLR)-4 antibodies inhibited LPS-induced NFκB activation in both hepatocytes and SECs. Furthermore, inhibitors of NFκB and MEK recovered the LPS-induced decreased expression of PS in both cell types and the LPS-induced decreased expression of C4BP in hepatocytes. These data suggest that the LPS-induced decrease in PS expression in hepatocytes and SECs and LPS-induced decrease in C4BP expression in hepatocytes are mediated by MEK/ERK signaling and NFκB activation and that membrane-bound CD14 and TLR-4 are involved in this mechanism.

C4BPB/C4BPA is a new susceptibility locus for venous thrombosis with unknown protein S-independent mechanism: results from genome-wide association and gene expression analyses followed by case-control studies

Through its binding with protein S (PS), a key element of the coagulation/fibrinolysis cascade, the C4b-binding protein (C4BP) has been hypothesized to be involved in the susceptibility to venous thrombosis (VT). To identify genetic factors that may influence the plasma levels of the 3 C4BP existing isoforms, alpha(7)beta(1), alpha(6)beta(1), and alpha(7)beta(0), we conducted a genome-wide association study by analyzing 283 437 single nucleotide polymorphisms (SNPs) in the Genetic Analysis of Idiopathic Thrombophilia (GAIT) study composed of 352 persons. Three SNPs at the C4BPB/C4BPA locus were found genome-wide significantly associated with alpha(7)beta(0) levels. One of these SNPs was further found to explain approximately 11% of the variability of mRNA C4BPA expression in the Gutenberg Heart Study composed of 1490 persons, with no effect on C4BPB mRNA expression. The allele associated with increased alpha(7)beta(0) plasma levels and increased C4BPA expression was further found associated with increased risk of VT (odds ratio [OR] = 1.24 [1.03-1.53]) in 2 independent case-control studies (MARseille THrombosis Association study [MARTHA] and FActeurs de RIsque et de récidives de la maladie thromboembolique VEineuse [FARIVE]) gathering 1706 cases and 1379 controls. This SNP was not associated with free PS or total PS. In conclusion, we observed strong evidence that the C4BPB/C4BPA locus is a new susceptibility locus for VT through a PS-independent mechanism that remains to be elucidated.

Upregulation of protein S by progestins

BACKGROUND

Users of progestin-only contraceptives have raised protein S (PS) levels compared with baseline. This contrasts with the reduction in PS levels observed in users of combined oral contraceptives, which contain both a progestin and an estrogen.

OBJECTIVES

To determine the effect of progesterone and other progestin isoforms on the expression of PS and to describe the mechanism involved.

METHODS

Promoter activity of the PROS1 gene that encodes PS was assessed in vitro using breast and liver carcinoma cell lines grown in the presence of various progestins, with and without the addition of excess progesterone receptors. An electromobility shift assay (EMSA) was also performed to identify the progesterone receptor binding element.

RESULTS

PROS1 transcriptional levels were directly upregulated by 25% by progesterone via a mechanism that was progesterone receptor isoform B (PR-B)-dependent. The process was blocked by the progesterone receptor modulator RU486. Results for the EMSA demonstrated that a probe comprising nucleotides -397 to -417 of the PROS1 promoter bound to ligand-activated PR-B, suggesting that the domain is a progesterone response element (PRE). The type of progestin isoform greatly influenced the level of PROS1 promoter upregulation, with medroxyprogesterone able to stimulate a > 2-fold stronger response compared with progesterone.

CONCLUSIONS

The PROS1 promoter is responsive to progesterone and other progestins via a mechanism involving PR-B interacting with a PRE. The type of progestin is important as some elicit stronger upregulatory effects than others, which may influence the choice of progestin used for hormonal contraception by PS-deficient individuals.