High Temperature Requirement A1 Research Articles

High-Temperature Requirement A1 Protease as a Rate-Limiting Factor in the Development of Osteoarthritis

Preserving the mature articular cartilage of joints is a critical focus in the prevention and treatment of osteoarthritis. We determined whether the genetic inactivation of high-temperature requirement A1 (HtrA1) can significantly attenuate the degradation of articular or condylar cartilage. Two types of mouse models of osteoarthritis were used, a spontaneous mutant mouse model [type XI collagen-haploinsufficient (Col11a1+/-) mice] and two post-traumatic mouse models [destabilization of the medial meniscus (DMM) on the knee and a partial discectomy (PDE) on the temporomandibular joint]. Three different groups of mice were generated: i) HtrA1 was genetically deleted from Col11a1+/- mice (HtrA1-/-;Col11a1+/-), ii) HtrA1-deficient mice (HtrA1-/-) were subjected to DMM, and iii) HtrA1-/- mice were subjected to PDE. Knee and temporomandibular joints from the mice were characterized for evidence of cartilage degeneration. The degradation of articular or condylar cartilage was significantly delayed in HtrA1-/-;Col11a1+/- mice and HtrA1-/- mice after DMM or PDE. The amount of collagen type VI was significantly higher in the articular cartilage in HtrA1-/-;Col11a1+/- mice, compared with that in Col11a1+/- mice. The genetic removal of HtrA1 may delay the degradation of articular or condylar cartilage in mice.

Placental HTRA1 Protease Cleaves Alpha-1-Antitrypsin and Generates Neonatal NET-Inhibitory Factor

BACKGROUND: Neutrophil extracellular traps (NET) are extracellular lattices of decondensed chromatin associated with anti-microbial proteins and degradative enzymes released by polymorphonuclear leukocytes (PMN) to trap and kill invading microbes. Dysregulated NET formation, however, contributes to inflammatory tissue damage. We have identified a novel NET-inhibitory peptide, neonatal NET-Inhibitory Factor (nNIF), present in the fetal circulation. nNIF is formed as a carboxy-terminus cleavage fragment of alpha-1 antitrypsin (AAT), an abundant, circulating protease inhibitor with homologs in human and mouse blood. However, the exact mechanisms by which nNIF is generated in fetal and neonatal blood remains unknown.OBJECTIVE: High temperature requirement A 1 (HTRA1) is expressed in the placenta during fetal development and inhibits AAT. We hypothesized that placentally expressed HTRA1, a serine protease, regulates the formation of NET-inhibitory peptides, such as nNIF, through cleavage of AAT.DESIGN/METHODS: Term and preterm placenta were lysed and probed for HTRA1 expression. HTRA1 and AAT plasma expression from term and preterm infants and adults were determined by ELISA. Recombinant, bioactive HTRA1 or placenta-eluted HTRA1 were incubated with AAT and the generation of carboxy-terminus fragments of AAT was assessed using western blotting and mass spectrometry. Fragments of AAT generated by HTRA1 were incubated with LPS-stimulated PMNs and NET formation was examined qualitatively using live cell imaging and quantitatively using a high throughput fluorescence assay. The effect of the HTRA-AAT cleavage fragment on reactive oxygen species generation, neutrophil chemotaxis, phagocytosis, and bacterial killing was measured using flow cytometry, a modified Boyden chamber asssay, neutrophil labeled Escherichia coli uptake assay, and a bacterial killing assay with a pathogenic strain of Escherichia coli, respectively. Finally, NET formation was evaluated qualitatively and quantitatively in murine PMNs isolated from neonatal WT and HTRA1-/- pups between 1-3, 4-6 and 7-10 days after birth to determine when PMNs become NET-competent.RESULTS: Term and preterm infant placentas express HTRA1, and we detected significantly (p<0.05) higher levels of HTRA1 in plasma from term (465.1±71.8 µg/mL) and preterm (385.9±71.3 µg/mL) infant cord blood compared to adults (58.6±11.6 µg/mL). Recombinant, bioactive HTRA1 and placenta-derived HTRA1 incubated with AAT generate a 4kD AAT fragment based on western blot and mass spectrometry similar to the nNIF fragment found in cord blood from term and preterm infants. Pre-incubation of this fragment with LPS-stimulated PMNs significantly inhibits NET formation (p<0.05). The cleavage fragment from HTRA1-AAT, however, has no effect on reactive oxygen species generation, chemotaxis, or phagocytosis. However, incubation of this fragment with LPS-stimulated PMNs significantly (p<0.05) reduces NET-associated bacterial killing by 62% compared to a scrambled HTRA-AAT control peptide. In addition, the HTRA1-AAT fragment significantly (p<0.05) reduces nuclear decondensation by 93% compared to LPS-stimulated PMN, suggesting this fragment inhibits PAD4 activation similar to other NIFs previously examined. Neonatal murine plasma contains a 4kD AAT fragment which inhibits NET formation by adult mouse PMNs, indicating that nNIF generation is conserved in mice. Neonatal PMNs stimulated with LPS exhibit delayed NET formation following birth with PMNs becoming NET-competent by day 8 of life. However, neonatal PMNs from pups born from HTRA1-/- deficient mice generate significantly (p<0.05) more NETs between day 4-6 of life compared to WT controls, suggesting that HTRA1 regulates NET formation through nNIF production.CONCLUSIONS: Placental HTRA1 interacts with AAT to generate a carboxy-terminus cleavage fragment of AAT with identical NET-inhibitory properties to nNIF. Our data strongly indicate that placental HTRA1 generates nNIF in the fetal circulation. We speculate that nNIF participates in the required tolerance to new microbial antigens encountered during the transition to extrauterine life. DisclosuresNo relevant conflicts of interest to declare.

High-Temperature Requirement A 1 Causes Photoreceptor Cell Death in Zebrafish Disease Models

Age-related macular degeneration (AMD) is an important cause of blindness. It is characterized by a retinal pigment epithelium (RPE) disorder that leads to death of photoreceptor cells (PRCs). AMD has a strong genetic association with high-temperature requirement A 1 (HTRA1). The relationship between HTRA1 and the AMD phenotype is unknown. In this study, we show that the expression of HTRA1 in PRCs, as well as in RPE, is increased by the disease-associated HTRA1 mutation and aging. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and quantitative PCR of apoptosis-associated caspases confirmed that PRC-specific overexpression of HTRA1 induced PRC death. Transgenic zebrafish overexpressing human HTRA1 in rod PRCs showed morphologic changes of the RPE, including PRC death and lipofuscin accumulation, features similar to those of early AMD. htra1 expression was also increased in a retinitis pigmentosa zebrafish model compared with wild type. In both fish lines, PRC death was rescued by the suppression of htra1 by the inhibitor 6-boroV. AKT-forkhead box O3 signaling downstream of HTRA1 was activated via a tumor growth factor β signal, resulting in PRC death. These findings suggest that HTRA1 derived from PRCs is associated with early AMD via PRC death. HTRA1 is a potentially effective target for neuroprotective therapy of early AMD and other degenerative diseases of PRCs.

Anti-rheumatoid arthritis effects in adjuvant-induced arthritis in rats and molecular docking studies of Polygonum orientale L. extracts

Background and purposePolygonum orientale L. (family: Polygonaceae), named Hongcao in China, has effects of dispelling wind and dampness, promoting blood circulation, and relieving pain. Our group has already studied and confirmed that POEa and POEe (ethyl acetate and ethyl ether extract of P. orientale, respectively) had anti-inflammatory and analgesic effects in early research, which was mainly relevant to the existence of flavonoids. According to the clinical application of P. orientale in traditional Chinese medicine, it has long been used for rheumatic arthralgia and rheumatoid arthritis. Therefore, our group further explored whether flavonoids of P. orientale have anti-rheumatoid arthritis effect and how does they play this role. MethodsDried small pieces of the stems and leaves of P. orientale were decocted with water and partitioned successively to obtain POEa and POEe, respectively. The anti-rheumatoid arthritis effect of P. orientale was studied by using a Freund's complete adjuvant (FCA)-induced arthritis (AIA) in a rat model. The levels of PGE2, TNF-α, and IL-1β in serum of AIA rats were detected by enzyme linked immunosorbent assay (ELISA) to explore its mechanisms. In addition, we computationally studied the relationships between the 15 chemical components of POEa and POEe, and the currently focused 9 target proteins of rheumatoid arthritis by molecular docking. ResultsPharmacological experiments showed that POEa and POEe significantly ameliorate symptoms of rheumatoid arthritis via reducing paw swelling volume, arthritis score, and thymus and spleen indices, as well as increasing body weight in AIA rats. Simultaneously, the concentrations of PGE2, TNF-α, and IL-1β were significantly decreased by POEa and POEe. Histopathology revealed noticeable reduction in bone and cartilage, synovial hyperplasia, inflammatory cell infiltration, cartilage surface erosion, and joint degeneration by POEa and POEe treatment. In addition, the molecular docking studies showed that docking scores of 14 chemical compositions (including 12 flavonoids and 2 phenolic acids) of POEa and POEe with anti-rheumatoid arthritis protein targets were better than the complexed ligands of the anti-rheumatoid arthritis protein targets. Among them, six flavonoids in POEa and POEe had more docking protein targets (n ≥ 3). Five anti-rheumatoid arthritis targets including high-temperature requirement A1 protease (HtrA1), janus kinase 1 (JAK1), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (i-NOS), and prostaglandin E2 (PGE2) had better docking score compared with the complexed ligands. Moreover, most of the chemical components in POEa and POEe showed strong interaction with HtrA1. ConclusionsThe flavonoids of P. orientale have anti-rheumatoid arthritis effect. In addition, the molecular docking results indicate that quercetin, catechol, orientin, and other six flavonoids may be closely related to HtrA1, JAK1, COX-2, i-NOS, and PGE2 protein target receptors. It suggests that these chemical compositions form strong protein-ligand complexes with these protein targets, especially HtrA1 to exert anti-rheumatoid arthritis. Further experimental studies show that mechanisms of anti-rheumatoid arthritis effects may also be relevant to inhibit the levels of PGE2, TNF-α, and IL-1β in serum. Therefore, our group can further explore the possible active ingredients and mechanisms of the anti-rheumatoid arthritis effects of flavonoids, and focus on the inhibition of the expression of inflammatory factors and the TGF-β1/Smad signaling pathway associated with HtrA1 protein target receptors, which can provide a direction and powerful reference for the action mechanism and drug research of anti-rheumatoid arthritis of flavonoids in P. orientale.

Single-walled carbon nanotubes affect the expression of genes associated with immune response in normal human astrocytes

The effect of single-walled carbon nanotubes (SWCNTs) on the expression of a subset of immune response, apoptosis and cell proliferation –associated genes was studied in normal human astrocytes (line NHA/TS). In the cells treated with SWCNTs (2, 10 and 50 ng/ml of medium for 24 h) we observed a strong dose-dependent down-regulation of the expression of a cell surface glycoproteins HLA-DRA (major histocompatibility complex, class II, DR alpha) and HLA-DRB1. At the same time, the expression of HLA-F (major histocompatibility complex, class I, F), LMNB1 (lamin B1), and HTRA1 (high temperature requirement A1) genes as well as the level of miR-190b and miR-7 was up-regulated in NHA/TS subjected to different concentrations of SWCNTs. After 24 h of treatment with SWCNTs we detected a dose-dependent suppression of PHLDA2 (pleckstrin homology-like domain, family A, member 2) gene expression in these cells. Obtained data show that SWCNTs may affect an immune response, in particular through suppression of HLA-DRA and HLA-DRB1 gene expressions and that miR-190b and miR-7 possibly participated in this suppression. Deregulation of lamin B1 expression indicates the possibility of alterations in genome stability following treatment of astrocytes with SWCNTs. Thus, more caution is needed in biomedical application of SWCNTs.

High-Temperature Requirement A1 (Htra1) - A Novel Regulator of Canonical Wnt Signaling

Different cancer types as well as many other diseases are caused by aberrant activation of the canonical Wnt signal transduction pathway, and it is especially implicated in the development and progression of colorectal cancer (CRC). The main effector protein of the canonical Wnt signaling cascade is β-catenin, which binds to the T- cell factor/lymphoid enhancer factor (TCF/LEF) and triggers the activation of Wnt target genes. Here, we identify the serine protease High-Temperature Requirement A1 (HTRA1) as a novel component of the canonical Wnt pathway. We show that the HTRA1 protein inhibits the Wnt/β-catenin signaling, in both paracrine and autocrine manners, and affects the expression of several Wnt target genes. Moreover, HTRA1 forms a complex with β-catenin and reduces the proliferation rates of cells. Taken together, our findings indicate that HTRA1 functions as a novel suppressor of the canonical Wnt signaling pathway.

Copy number variation in VEGF gene as a biomarker of susceptibility to age-related macular degeneration

BackgroundSeveral studies in various populations have been conducted to determine candidate genes that could contribute to age-related macular degeneration (AMD) pathogenesis. ObjectiveThe present study was undertaken to determine the association of high temperature requirement A-1 (HTRA1), vascular endothelial growth factor (VEGF) and very-low-density receptor (VLDR) genes with wet AMD subjects in Malaysia. MethodsA total of 125 subjects with wet AMD and 120 subjects without AMD from the Malaysian population were selected for this study. Genomic DNA was extracted and copy number variations (CNVs) were determined using quantitative real-time Polymerase Chain Reaction (qPCR) and comparison between the two groups was done. The demographic characteristics were also recorded. Statistical analysis was carried out using software where a level of P<0.05 was considered to be statistically significant. ResultStatistically significant associations of the VEGF gene were observed in mean copy differences between case and control subjects (P<0.05). The consistency of both unadjusted and age-adjusted data at Copy Number CN gain (CN=3 and CN=4) suggested that VEGF could increase the risk of wet AMD disease (P<0.05). None of CNVs of HTRA1 and VLDR genes showed associations with the wet AMD disease based on comparisons of the frequencies of mean (P>0.05). ConclusionObservations of an association between CNVs of VEGF gene and wet AMD have revealed that the CNVs of VEGF gene appears to be a possible contributor to wet AMD subjects in Malaysia.

ER stress-induced aggresome trafficking of HtrA1 protects against proteotoxicity

High temperature requirement A1 (HtrA1) belongs to an ancient protein family that is linked to various human disorders. The precise role of exon 1-encoded N-terminal domains and how these influence the biological functions of human HtrA1 remain elusive. In this study, we traced the evolutionary origins of these N-terminal domains to a single gene fusion event in the most recent common ancestor of vertebrates. We hypothesized that human HtrA1 is implicated in unfolded protein response. In highly secretory cells of the retinal pigmented epithelia, endoplasmic reticulum (ER) stress upregulated HtrA1. HtrA1 co-localized with vimentin intermediate filaments in highly arborized fashion. Upon ER stress, HtrA1 tracked along intermediate filaments, which collapsed and bundled in an aggresome at the microtubule organizing center. Gene silencing of HtrA1 altered the schedule and amplitude of adaptive signaling and concomitantly resulted in apoptosis. Restoration of wild-type HtrA1, but not its protease inactive mutant, was necessary and sufficient to protect from apoptosis. A variant of HtrA1 that harbored exon 1 substitutions displayed reduced efficacy in rescuing cells from proteotoxicity. Our results illuminate the integration of HtrA1 in the toolkit of mammalian cells against protein misfolding and the implications of defects in HtrA1 in proteostasis.

High temperature requirement A1 and fibronectin: two possible players in placental tissue remodelling.

High temperature requirement A1 (HtrA1) is a secreted protease involved in placental development. Fibronectin (FN) is involved in important process such as wound healing, cell adhesion and spreading, growth, migration, and differentiation. The purpose of this study was to analyse the expression patterns of HtrA1 in relationship to FN and to the key growth zones of placenta such as mesenchymal villi as well as cell islands and cell columns. We demonstrated that FN and HtrA1 are localized in the placental key growth zones suggesting a pivotal role in maintaining the balance among the molecules involved in the placental development and differentiation.

High temperature requirement A1, transforming growth factor beta1, phosphoSmad2 and Ki67 in eutopic and ectopic endometrium of women with endometriosis.

Increasing evidence supports the hypothesis that TGFβ1 signalling may be mediated by high temperature requirement A1 (HtrA1) serine protease, acting on important regulatory mechanisms such as cell proliferation and mobility. Evidence is now accumulating to suggest that HtrA1 is involved in the development and progression of several pathologies. The aim of this study was to evaluate: i) if HtrA1 and TGFβ1 expressions differ in eutopic and ectopic endometrium in women with endometriosis; ii) if HtrA1 correlates to TGFβ1, pSmad and Ki67. This study was carried out including 10 women with ovarian endometriosis (cases) and 10 women with non endometriotic diseases (controls). Endometrial tissue underwent immunohistochemical H-score analysis for HtrA1, TGFβ1, pSmad and Ki67 molecules. Data evaluation was performed by a nonparametric Kruskal-Wallis test and Spearman correlation was applied to evaluate the relationship among the molecules investigated in the epithelial and in the stromal compartment. The HtrA1 was significantly decreased in ectopic and eutopic endometrium of women with endometriosis when compared with control endometrium in epithelial compartment. TGFβ1was significantly increased in eutopic endometrium and decreased in ectopic endometrium in epithelial and stromal compartment. In addition, Ki67 was significantly increased and an increase, but not significant, was detected for pSMAd2 in eutopic and ectopic endometrium compared to control one. In summary, the significant direct correlation between TGFβ1 and pSmad2 as well as between HtrA1 and TGFβ1 and the very significant increase of Ki67 in stromal compartment of eutopic endometrium suggest a possible involvement of HtrA1 in the pathogenesis of endometriosis.

Synonymous variants in HTRA1 implicated in AMD susceptibility impair its capacity to regulate TGF-β signaling.

High-temperature requirement A1 (HTRA1) is a secreted serine protease reported to play a role in the development of several cancers and neurodegenerative diseases. Still, the mechanism underlying the disease processes largely remains undetermined. In age-related macular degeneration (AMD), a common cause of vision impairment and blindness in industrialized societies, two synonymous polymorphisms (rs1049331:C>T, and rs2293870:G>T) in exon 1 of the HTRA1 gene were associated with a high risk to develop disease. Here, we show that the two polymorphisms result in a protein with altered thermophoretic properties upon heat-induced unfolding, trypsin accessibility and secretion behavior, suggesting unique structural features of the AMD-risk-associated HTRA1 protein. Applying MicroScale Thermophoresis and protease digestion analysis, we demonstrate direct binding and proteolysis of transforming growth factor β1 (TGF-β1) by normal HTRA1 but not the AMD-risk-associated isoform. As a consequence, both HTRA1 isoforms strongly differed in their ability to control TGF-β mediated signaling, as revealed by reporter assays targeting the TGF-β1-induced serpin peptidase inhibitor (SERPINE1, alias PAI-1) promoter. In addition, structurally altered HTRA1 led to an impaired autocrine TGF-β signaling in microglia, as measured by a strong down-regulation of downstream effectors of the TGF-β cascade such as phosphorylated SMAD2 and PAI-1 expression. Taken together, our findings demonstrate the effects of two synonymous HTRA1 variants on protein structure and protein interaction with TGF-β1. As a consequence, this leads to an impairment of TGF-β signaling and microglial regulation. Functional implications of the altered properties on AMD pathogenesis remain to be clarified.

Serum HtrA1 is differentially regulated between early-onset and late-onset preeclampsia

HtrA1 (high temperature requirement A1) is a serine protease of the HtrA family. We have previously shown that the placenta expresses the highest level of HtrA1 mRNA compared to other tissues in the human. Others have reported that placental HtrA1 is significantly up-regulated in preeclampsia (PE), a pregnancy-specific multi-systemic disorder associated with new onset hypertension and proteinuria. However, it is unclear how serum HtrA1 changes in a normal pregnancy and whether it is altered in PE pregnancies. A sandwich ELISA highly specific to human HtrA1 and suitable for serum detection was developed and thoroughly validated. This assay was then applied to serum samples from different stages of normal pregnancy, as well as early-onset (<34 weeks) and late-onset (>34 weeks) PE pregnancies. Serum HtrA1 increased progressively with increasing gestation in normal pregnancies. However, this trend was perturbed in women with PE. Compared to respective gestation-age-matched normal pregnancies, HtrA1 serum levels were significantly increased in early-onset PE, but significantly reduced in late-onset PE. This is the first report to show a clear increase of HtrA1 in the maternal circulation during normal pregnancy, consistent with HtrA1 being highly expressed in the placenta. Importantly, this study identified that serum HtrA1 was altered differently in early-onset and late-onset PE pregnancies, highlighting the complex regulation of HtrA1 in the different subtypes. The significant increase of serum HtrA1 in early-onset PE suggests that it may be a potential biomarker for the diagnosis of early-onset PE at disease presentation.

High systemic LDL cholesterol levels during experimental osteoarthritis lead to increased synovial activation and ectopic bone formation at end-stage osteoarthritis, while excessive levels accelerate development of joint pathology already at early-stage of osteoarthritis

High systemic LDL cholesterol levels during experimental osteoarthritis lead to increased synovial activation and ectopic bone formation at end-stage osteoarthritis, while excessive levels accelerate development of joint pathology already at early-stage of osteoarthritis

Target-based screen against a periplasmic serine protease that regulates intrabacterial pH homeostasis in Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) maintains its intrabacterial pH (pHIB) near neutrality in the acidic environment of phagosomes within activated macrophages. A previously reported genetic screen revealed that Mtb loses this ability when the mycobacterial acid resistance protease (marP) gene is disrupted. In the present study, a high throughput screen (HTS) of compounds against the protease domain of MarP identified benzoxazinones as inhibitors of MarP. A potent benzoxazinone, BO43 (6-chloro-2-(2′-methylphenyl)-4H-1,3-benzoxazin-4-one), acylated MarP and lowered Mtb’s pHIB and survival during incubation at pH 4.5. BO43 had similar effects on MarP-deficient Mtb, suggesting the existence of additional target(s). Reaction of an alkynyl-benzoxazinone, BO43T, with Mycobacterium bovis variant bacille Calmette-Guérin (BCG) followed by click chemistry with azido-biotin identified both the MarP homologue and the high temperature requirement A1 (HtrA1) homologue, an essential protein. Thus, the chemical probe identified through a target-based screen not only reacted with its intended target in the intact cells but also implicated an additional enzyme that had eluded a genetic screen biased against essential genes.

Prognostic phenotypic and genotypic factors associated with photodynamic therapy response in patients with age-related macular degeneration.

BackgroundThis study aimed to demonstrate the phenotypic and genotypic factors associated with photodynamic therapy (PDT) for age-related macular degeneration (AMD).MethodsThe study included 149 patients with exudative AMD treated by PDT. Eight phenotypic factors and ten genotypic factors for three single nucleotide polymorphisms (SNPs; rs800292, rs1061170, rs1410996) in the complement factor H (CFH) gene, rs 11200638-SNP in the high temperature requirement A-1 (HTRA1) gene, two SNPs (rs699947, rs2010963) in the vascular endothelial growth factor (VEGF) gene, and four SNPs (rs12948385, rs12150053, rs9913583, rs1136287) in the pigment epithelium-derived factor (PEDF) gene were evaluated.ResultsA significant association with best-corrected visual acuity change was demonstrated in the greatest linear dimension, presence or absence of pigment epithelial detachment, and HTRA1-rs11200638 genotype statistically (P=3.67×10−4, 1.95×10−2, 1.24×10−3, respectively). Best-corrected visual acuity in patients with AA genotype of HTRA1-rs11200638 significantly decreased compared with that in patients with GG genotype (P=1.33×10−3). Logistic regression analyses demonstrated HTRA1-rs11200638 genotype was most strongly associated with best-corrected visual acuity outcome from baseline at 12 months after photodynamic therapy (P=4.60×10−3; odds ratio 2.363; 95% confidence interval 1.303–4.285).ConclusionThe HTRA1-rs11200638 variant showed the most significant association. Therefore, this variant may be used as a prognostic factor to estimate the PDT response with significant predictive power.

Abnormal development of placenta in HtrA1-deficient mice

Abnormal levels of High temperature requirement A1 (HtrA1) protein have been repeatedly observed in sera and placentas of preeclampsia patients. To understand the functions of HtrA1 in placentation and in the etiology of preeclampsia, we established HtrA1−/− mice. HtrA1−/− mice show intrauterine growth retardation, and their placentas are small due to a reduced size of the junctional zone and aberrant vascularization in the labyrinth at the mid-gestation stage. HtrA1 is expressed by Tpbpa-positive trophoblast precursors in the outer ectoplacental cone and junctional zone from embryonic day 7.5 to 10.5. In the HtrA1−/− placenta, Tpbpa-positive cell precursors are decreased in the early stage. Spongiotrophoblasts and glycogen trophoblast cells, both of which differentiate from Tpbpa-positive precursors, are consequently decreased in the junctional zone. Fewer spiral artery-associated trophoblast giant cells, another cell type derived from Tpbpa-positive precursors, invade the decidua and associate with maternal arteries in the HtrA1−/− placenta than in the wild type placenta. Maternal arteries in the HtrA1−/− decidua have narrower lumens, thicker arterial walls, and more vascular smooth muscle cells remaining in the walls than those in the wild type decidua, indicating impaired remodeling of maternal arteries. These results indicate that HtrA1 plays important roles in the differentiation of trophoblasts from Tpbpa-positive precursors in the ectoplacental cone. Insufficient levels of HtrA1 cause poor placental development and intrauterine growth retardation, due to aberrant trophoblast differentiation and consequent defects in maternal artery remodeling, and may contribute to the onset of preeclampsia.

Alpha-1-Antitrypsin: A Novel Human High Temperature Requirement Protease A1 (HTRA1) Substrate in Human Placental Tissue

The human serine protease high temperature requirement A1 (HTRA1) is highly expressed in the placental tissue, especially in the last trimester of gestation. This suggests that HTRA1 is involved in placental formation and function. With the aim of a better understanding of the role of HTRA1 in the placenta, candidate substrates were screened in a placenta protein extract using a gel-based mass spectrometric approach. Protease inhibitor alpha-1-antitrypsin, actin cytoplasmic 1, tropomyosin beta chain and ten further proteins were identified as candidate substrates of HTRA1. Among the identified candidate substrates, alpha-1-antitrypsin (A1AT) was considered to be of particular interest because of its important role as protease inhibitor. For investigation of alpha-1-antitrypsin as substrate of HTRA1 synthetic peptides covering parts of the sequence of alpha-1-antitrypsin were incubated with HTRA1. By mass spectrometry a specific cleavage site was identified after met-382 (AIPM382↓383SIPP) within the reactive centre loop of alpha-1-antitrypsin, resulting in a C-terminal peptide comprising 36 amino acids. Proteolytic removal of this peptide from alpha-1-antitrypsin results in a loss of its inhibitor function. Beside placental alpha-1-antitrypsin the circulating form in human plasma was also significantly degraded by HTRA1. Taken together, our data suggest a link between the candidate substrates alpha-1-antitrypsin and the function of HTRA1 in the placenta in the syncytiotrophoblast, the cell layer attending to maternal blood in the villous tree of the human placenta. Data deposition: Mass spectrometry (MS) data have been deposited to the ProteomeXchange with identifier PXD000473.

The inhibitory effect of IFN-γ on protease HTRA1 expression in rheumatoid arthritis.

The high temperature requirement A1 (HTRA1) is a potent protease involved in many diseases, including rheumatoid arthritis (RA). However, the regulatory mechanisms that control HTRA1 expression need to be determined. In this study, we demonstrated that IFN-γ significantly inhibited the basal and LPS-induced HTRA1 expression in fibroblasts and macrophages, which are two major cells for HTRA1 production in RA. Importantly, the inhibitory effect of IFN-γ on HTRA1 expression was evidenced in collagen-induced arthritis (CIA) mouse models and in human RA synovial cells. In parallel with the enhanced CIA incidence and pathological changes in IFN-γ-deficient mice, HTRA1 expression in the joint tissues was also increased as determined by real-time PCR and Western blots. IFN-γ deficiency increased the incidence of CIA and the pathological severity in mice. Neutralization of HTRA1 by Ab significantly reversed the enhanced CIA frequency and severity in IFN-γ-deficient mice. Mechanistically, IFN-γ negatively controls HTRA1 expression through activation of p38 MAPK/STAT1 pathway. Dual luciferase reporter assay and chromatin immunoprecipitation analysis showed that STAT1 could directly bind to HTRA1 promoter after IFN-γ stimulation. This study offers new insights into the molecular regulation of HTRA1 expression and its role in RA pathogenesis, which may have significant impact on clinical therapy for RA and possibly other HTRA1-related diseases, including osteoarthritis, age-related macular degeneration, and cancer.

Expression and localization of serine protease Htra1 in neuroblastoma: correlation with cellular differentiation grade

Neuroblastoma (NB) is a paediatric tumor that arises from neural crest and shows heterogeneous clinical and biological features. The serine-protease high temperature requirement A1 (HtrA1) has a pivotal role in both cell proliferation and differentiation. Here we report the expression and localization of HtrA1 in NB tumor samples to assess HtrA1 role as a possible new biomarker of cellular differentiation in NB patients. HtrA1 protein expression by Western Blot assay was performed in 60 tissue samples of 50 children with NB and 10 children with ganglioneuroblastoma (GNB). HtrA1 was expressed in 56/60 (93.3%) samples with different expression levels: low levels in 36/56 samples (64.3%) and high levels in 20/56 (35.7%). Higher levels were found in 1, 2 and 4s stages (80%), whereas 3 and 4 stages (20%) showed a low expression, with a statistically significant difference (p=0.003). Among not amplified N-MYC group, 28 (60%) had low/absent expression of HtrA1: seven with recurrent disease and negative outcome and 21 in continuous complete remission (CCR), whereas all samples with high expression of HtrA1 (17/44) were in CCR (p=0.03). The immunohistochemical analysis showed localization of HtrA1 in differentiated areas higher than in undifferentiated areas where the protein was absent. Moreover, HtrA1 was highly expressed in all GNB samples. In conclusion, the over-expression of HtrA1 is correlated to cellular differentiation grade and stage of NB at diagnosis. Moreover, HtrA1 could represent a new marker of undifferentiation and biological aggressiveness of NB.

Induction of high temperature requirement A1, a serine protease, by TGF-beta1 in articular chondrocytes of mouse models of OA.

The goal of this study is to determine whether transforming growth factor beta 1 (Tgf-β1) induces the high temperature requirement A1 (HtrA1) in articular chondrocytes of two mouse models of osteoarthritis (OA). Early onset articular cartilage degeneration in the mouse models was characterized by histology. Expression profiles of Tgf-β1, p-Smad1, p-Smad2/3 and HtrA1 in knee joints of the mouse models were examined by immunofluorescene. By in vitro and ex vivo experiments, human primary chondrocytes and articular cartilages from femoral condyles of mice were treated with recombinant human TGF-β1 and an ALK5 chemical inhibitor, SB431542. The level of HTRA1 mRNA in human and mouse articular chondrocytes was examined by real-time PCR. Chondrocyte clusters were present in the articular cartilage of knee joints in the mouse models. Increased expressions of Tgf-β1, p-Smad2/3 and HtrA1 were detected in the articular chondrocyte of knee joints in the mouse models. The increased expressions of p-Smad2/3 and HtrA1 were co-localized in the articular chondrocyte of the knee joints. The expression of p-Smad1 was hardly detectable in the mouse models and their corresponding wild-type littermates. The level of HTRA1 mRNA was increased in human and mouse articular chondrocytes treated with TGF-β1, compared with that in chondrocytes without the treatment of TGF-β1. The TGF-β1-induced expression of HTRA1 in human and mouse articular chondrocytes was inhibited by SB431542. These results suggest that the Tgf-β1 canonical signaling was activated to induce HtrA1 in the articular chondrocytes of the mouse models of OA.