Implications of proprotein Convertase 5 (PC5) in the arterial restenotic process in a porcine model

Association of Anti-Mullerian Hormone with C-Reactive Protein in Men

While serum anti-mullerian hormone (AMH) levels are inversely associated with all-cause mortality in men, the underlying mechanisms are unclear. Elevated levels of inflammation, also associated with all-cause mortality, and may be the link between AMH and mortality. Hence, we examined the association of AMH with serum c-reactive protein (CRP), a biomarker of inflammation, in men. We included men ≥20 years from the National Health and Nutrition Examination Survey (1999–2004). We used survey weight-adjusted linear regression to examine the association between AMH and CRP without and with adjustment for age, race, body mass index (BMI), smoking, hypertension, diabetes, cholesterol, glomerular filtration rate (GFR), testosterone, androstenedione, and sex hormone binding globulin. Of the 949 men, 212 (22%) were elderly, 493 (52%) Caucasian, 254 (27%) current smokers, 100 (10%) diabetics, and 312 (33%) had hypertension. Mean (SD) AMH was 8.4 (7.2) ng/mL and median (IQR) CRP level was 0.17 (3) mg/L. Using linear regression, each 10 ng/mL rise in AMH was associated with 0.09 mg/dL (95%CI = −0.14 to −0.03; p = 0.002) decrease before and 0.08 mg/dL (95%CI = −0.13 to −0.02; p = 0.004) decrease in CRP after adjusting for potential confounders. Similarly, men in the highest quartile of AMH had significantly lower CRP compared to those in the lowest quartile (unadjusted difference = −0.19 mg/dL; 95%CI = −0.31 to −0.06; p = 0.006, adjusted difference = −0.16 mg/dL; 95%CI = −0.3 to −0.01; p = 0.035). We found an independent, robust, and inverse association between CRP and AMH in men. Effect of AMH on mortality may be through amelioration of inflammation.

Anti-Müllerian hormone is a gonadal cytokine with two circulating forms and cryptic actions

Anti-Müllerian hormone (AMH) is a multi-faceted gonadal cytokine. It is present in all vertebrates with its original function in phylogeny being as a regulator of germ cells in both sexes, and as a prime inducer of the male phenotype. Its ancient functions appear to be broadly conserved in mammals, but with this being obscured by its overt role in triggering the regression of the Müllerian ducts in male embryos. Sertoli and ovarian follicular cells primarily release AMH as a prohormone (proAMH), which forms a stable complex (AMHN,C) after cleavage by subtilisin/kexin-type proprotein convertases or serine proteinases. Circulating AMH is a mixture of proAMH and AMHN,C, suggesting that proAMH is activated within the gonads and putatively by its endocrine target-cells. The gonadal expression of the cleavage enzymes is subject to complex regulation, and the preliminary data suggest that this influences the relative proportions of proAMH and AMHN,C in the circulation. AMH shares an intracellular pathway with the bone morphogenetic protein (BMP) and growth differentiation factor (GDF) ligands. AMH is male specific during the initial stage of development, and theoretically should produce male biases throughout the body by adding a male-specific amplification of BMP/GDF signalling. Consistent with this, some of the male biases in neuron number and the non-sexual behaviours of mice are dependent on AMH. After puberty, circulating levels of AMH are similar in men and women. Putatively, the function of AMH in adulthood maybe to add a gonadal influence to BMP/GDF-regulated homeostasis.

Human blood contains both the uncleaved precursor of anti-Mullerian hormone and a complex of the NH2- and COOH-terminal peptides

Anti-Müllerian hormone (AMH) in blood is a marker of ovarian status in women and the presence of cryptic testes in babies. Despite this, the molecular form of AMH in blood has not been verified. AMH is synthesized as an inert proprotein precursor (proAMH), which can be cleaved to yield NH2-terminal (AMHN) and COOH-terminal (AMHC) fragments, that can complex noncovalently (AMHN,C). Developing males have 10-fold more AMH than young adults. We report here that human blood is a mixture of inactive proAMH and receptor-binding AMHN,C. The AMH in the blood of boys, men, and premenopausal women was immunoprecipitated using antibodies to the NH2- and COOH-terminal peptides. The precipitated proteins were then analyzed by Western blots, using recombinant proteins as markers. The glycosylation status of AMH was verified using deglycosylating enzymes. The NH2-terminal antibody precipitated a major protein that migrated alongside rhproAMH and was detected by anti-AMHN and anti-AMHC. This antibody also precipitated significant levels of AMHN and AMHC from all participants. Antibodies specific to AMHC precipitated rhAMHC but did not precipitate AMHC from human blood. Hence, all the AMHC in human blood appears to be bound to AMHN. Both AMHN and proAMH were glycosylated, independent of age and sex. In conclusion, boys and young adults have the same form of AMH, with a significant proportion being the inactive precursor. This raises the possibility that the endocrine functions of AMH are partly controlled by its cleavage in the target organ. The presence of proAMH in blood may confound the use of AMH for diagnosis.

TGF-beta1 upregulation in the aging varicose vein

BACKGROUND

Although the etiology of venous insufficiency is not well understood, immune response and aging are beginning to emerge as contributing factors. Factors involved in tissue remodeling such as TGF-beta(1) also seem to play an important role in extracellular matrix production. The aim of this study was to explore the relationship between chronic venous insufficiency and TGF-beta(1) examining the latent/mature form of TGF-beta(1) and the presence of mast cells. Effects of age were also evaluated.

METHODS

Saphenous veins were obtained from patients subjected to aortocoronary bypass (controls) and undergoing varicose vein surgery. These were immunolabeled using anti-LAP TGF-beta(1)/anti-TGF-beta(1) antibodies and subjected to Western blot. Mast cell population was identified by metachromatic staining.

RESULTS

Latent TGF-beta(1) was significantly reduced in varicose veins from older subjects. In contrast, smooth muscle cells obtained from the varicosities showed intense levels. Mature TGF-beta(1) significantly differed between healthy and varicose veins. No mature TGF-beta(1) was detected in the cell cultures. Mast cell number and degranulation were increased with aging and varicose disease, colocalizing with the mature form of TGF-beta(1).

CONCLUSION

Aging and varicose pathology induce dysregulation of TGF-beta(1) that could play an important role in the fibrous process, representing the final stages of venous insufficiency.

Proprotein convertases furin and PC5: targeting atherosclerosis and restenosis at multiple levels

Several growth factors, chemokines, adhesion molecules, and proteolytic enzymes important for cell-cell/cell-matrix interactions in atherosclerosis and restenosis are initially synthesized as inactive precursor proteins. Activation of proproteins to biologically active molecules is regulated by limited endoproteolytic cleavage at dibasic amino acid residues. This type of activation typically requires the presence of suitable proprotein convertases (PCs). The PC-isozymes furin and PC5 are expressed in human atherosclerotic lesions and have been found to be up-regulated, following vascular injury in animal models in vivo. In vitro, these PCs can regulate vascular smooth muscle cell and macrophage functions and signaling events, through activation of pro-alpha-integrins and/or pro-membrane-type matrix metalloproteinases. Integrins link the cytoskeleton with the extracellular matrix and mediate bidirectional signaling and mechanotransduction, whereas matrix metalloproteinases are the major matrix-degrading enzymes. Both activities are required for cell recruitment to the intima. Furthermore, cleavage of extracellular matrix molecules by matrix metalloproteinases potentially contributes to weakening of the fibrous cap, promoting plaque rupture. Based on these recent in vitro and in vivo data, furin and PC5 are potential contributors to the initiation, progression, and complications of atherosclerosis and restenosis. Targeting these PCs may provide future anti-atherosclerotic therapies.