A novel discoidin domain receptor 1 (Ddr1) transcript is expressed in postmeiotic germ cells of the rat testis depending on the major histocompatibility complex haplotype

Fufangxiaopi formula alleviates DSS-induced colitis in mice by inhibiting inflammatory reaction, protecting intestinal barrier and regulating intestinal microecology

ETHNOPHARMACOLOGICAL RELEVANCE

Fufangxiaopi Formula (FF) is a modified form of Sishen Wan, traditionally used for treating diarrhea. The application of FF for treating ulcerative colitis (UC) has achieved desirable outcomes in clinical settings. However, the underlying mechanism of the effect of FF on UC is yet to be determined.

AIM OF STUDY

This study aimed to evaluate the protective effect and underlying mechanism of FF on mice with dextran sodium sulfate (DSS)-induced colitis.

MATERIALS AND METHODS

In vivo, the efficacy of FF on the symptoms associated with DSS-induced colitis in mice was clarified by observing the body weight change, colon length, DAI score, and H&E staining. The release of inflammatory mediators in mouse colon tissues was detected by ELISA and MPO, and the contents of TLR4/NF-κB signaling pathway and MAPK signaling pathway-related proteins, as well as intestinal barrier-related proteins, were detected in mouse colon tissues by western blot method. Changes in the content of barrier proteins in mouse colon tissues were detected by immunofluorescence. 16S rRNA sequencing and FMT were performed to clarify the effects of FF on intestinal flora. In vitro, the effect of FF-containing serum on LPS-induced inflammatory mediator release from RAW264.7 cells were detected by qRT-PCR. The contents of TLR4/NF The effects of FF-containing serum on B signaling pathway and MAPK signaling pathway related proteins in RAW264.7 cells and intestinal barrier related proteins in Caco-2 cells were detected by western blot. The effects of FF-containing serum on LPS-induced nuclear translocation of p65 protein in RAW264.7 cells and barrier-associated protein in Caco-2 cells were detected by immunofluorescence.

RESULTS

In vivo studies showed that FF could significantly alleviate the symptoms of UC, including reducing colon length, weight loss, clinical score, and colon tissue injury in mice. FF could significantly reduce the secretion of proinflammatory cytokines by suppressing the activation of the TLR4/NF-κB and MAPK signaling pathways. Moreover, FF could protect the integrity of intestinal barriers by significantly increasing claudin-3, occludin, and ZO-1 expression levels. 16S rRNA sequencing and FMT elucidate that FF can alleviate symptoms associated with colitis in mice by interfering with intestinal flora. In vitro studies showed that FF drug-containing serum could significantly inhibit proinflammatory responses and attenuate the secretion of iNOS, IL-1β, TNF-α, IL-6, and COX-2 by suppressing the activation of TLR4/NF-κB and MAPK signaling pathways in RAW264.7 cells. Furthermore, FF could protect the Caco-2 cell epithelial barrier.

CONCLUSION

FF could alleviate DSS-induced colitis in mice by maintaining the intestinal barrier, inhibiting the activation of TLR4/NF-κB and MAPK signaling pathways, reducing the release of proinflammatory factors, and regulating intestinal microecology.

Discoidin domain receptor 1 may be involved in biological barrier homeostasis

WHAT IS KNOWN AND OBJECTIVE

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase involved in the pathological processes of several diseases, such as keloid formation, renal fibrosis, atherosclerosis, tumours, and inflammatory processes. The biological barrier is the first line of defence against pathogens, and its disruption is closely related to diseases. In this review, we attempt to elucidate the relationship between DDR1 and the biological barrier, explore the potential biological value of DDR1, and review the current research status and clinical potential of DDR1-selective inhibitors.

METHODS

We conducted an extensive literature search on PubMed to collect studies on the relevance of DDR1 to biological barriers and DDR1-selective inhibitors. With these studies, we explored the relationship between DDR1 and biological barriers and briefly reviewed representative DDR1-selective inhibitors that have been reported in recent years.

RESULTS AND DISCUSSION

First, the review of the potential mechanisms by which DDR1 regulates biological barriers, including the epithelial, vascular, glomerular filtration, blood-labyrinth, and blood-brain barriers. In the body, DDR1 dysfunction and aberrant expression may be involved in the homeostasis of the biological barrier. Secondly, the review of DDR1 inhibitors reported in recent years shows that DDR1-targeted inhibition is an attractive and promising pharmacological intervention.

WHAT IS NEW AND CONCLUSIONS

This review shows that DDR1 is involved in various physiological and pathological processes and in the regulation of biological barrier homeostasis. However, studies on DDR1 and biological barriers are still scarce, and further studies are needed to elucidate their specific mechanisms. The development of targeted inhibitors provides a new direction and idea to study the mechanism of DDR1.

Discoidin Domain Receptors, DDR1b and DDR2, Promote Tumour Growth within Collagen but DDR1b Suppresses Experimental Lung Metastasis in HT1080 Xenografts

The Discoidin Domain Receptors (DDRs) constitute a unique set of receptor tyrosine kinases that signal in response to collagen. Using an inducible expression system in human HT1080 fibrosarcoma cells, we investigated the role of DDR1b and DDR2 on primary tumour growth and experimental lung metastases. Neither DDR1b nor DDR2 expression altered tumour growth at the primary site. However, implantation of DDR1b- or DDR2-expressing HT1080 cells with collagen I significantly accelerated tumour growth rate, an effect that could not be observed with collagen I in the absence of DDR induction. Interestingly, DDR1b, but not DDR2, completely hindered the ability of HT1080 cells to form lung colonies after intravenous inoculation, suggesting a differential role for DDR1b in primary tumour growth and lung colonization. Analyses of tumour extracts revealed specific alterations in Hippo pathway core components, as a function of DDR and collagen expression, that were associated with stimulation of tumour growth by DDRs and collagen I. Collectively, these findings identified divergent effects of DDRs on primary tumour growth and experimental lung metastasis in the HT1080 xenograft model and highlight the critical role of fibrillar collagen and DDRs in supporting the growth of tumours thriving within a collagen-rich stroma.

Dichotomy of the function of DDR1 in cells and disease progression

Discoidin domain receptors DDR1 and DDR2 are collagen receptor tyrosine kinases that have many roles in tissue development and disease progression. Under physiological conditions, DDR1 is predominantly expressed in epithelial cells and functions to maintain cell differentiation and tissue homeostasis. A switch in expression from DDR1 to DDR2 occurs during epithelial-to-mesenchymal transition. However, opposite effects of DDR1 are reported to be involved in the progression of cancer and fibrotic diseases. Accumulating evidence suggests that DDR1 is involved in pro-metastasis and pro-survival signals. This review summarizes the roles of DDR1 in epithelial cell differentiation, cell migration, cancer progression and tissues fibrosis and highlights how the dichotomous functions of DDR1 may relevant to different cell types and statues. Elucidation of the underlying mechanism of the dichotomous functions of DDR1 will help to develop DDR1 as a therapeutic target.

Signaling by discoidin domain receptor 1 in cancer metastasis

Collagen is the most abundant component of tumor extracellular matrix (ECM). ECM collagens are known to directly interact with the tumor cells via cell surface receptor and play crucial role in tumor cell survival and promote tumor progression. Collagen receptor DDR1 is a member of receptor tyrosine kinase (RTK) family with a unique motif in the extracellular domain resembling Dictyostelium discoideum protein discoidin-I. DDR1 displays delayed and sustained activation upon interaction with collagen and recent findings have demonstrated that DDR1-collagen signaling play important role in cancer progression. In this review, we discuss the current knowledge on the role of DDR1 in cancer metastasis and possibility of a potential therapeutic approach of DDR1 targeted therapy in cancer.

Spermatogenesis-associated 48 is essential for spermatogenesis in mice

Azoospermia, oligospermia and teratozoospermia all seriously impact male reproductive health. Spermatogenesis is a complex and precisely regulated process in which germ cells proliferate and differentiate and involves the regulation of multiple testis-specific genes. Here, we identified testis-specific gene spermatogenesis-associated 48 (SPATA48), the expression of which was age-dependent, indicating that it is involved in spermatogenesis. In humans and mice with azoospermia, expression of SPATA48 disappeared in the testis. Spata48-/- knockout male mice had smaller testis and defective spermatogenesis compared to wild-type (WT) mice. This study can help in the exploration of the genetic basis of male infertility and identify new targets for the diagnosis and treatment of male infertility.

Discoidin Domain Receptors: Potential Actors and Targets in Cancer

The extracellular matrix critically controls cancer cell behavior by inducing several signaling pathways through cell membrane receptors. Besides conferring structural properties to tissues around the tumor, the extracellular matrix is able to regulate cell proliferation, survival, migration, and invasion. Among these receptors, the integrins family constitutes a major class of receptors that mediate cell interactions with extracellular matrix components. Twenty years ago, a new class of extracellular matrix receptors has been discovered. These tyrosine kinase receptors are the two discoidin domain receptors DDR1 and DDR2. DDR1 was first identified in the Dictyostelium discoideum and was shown to mediate cell aggregation. DDR2 shares highly conserved sequences with DDR1. Both receptors are activated upon binding to collagen, one of the most abundant proteins in extracellular matrix. While DDR2 can only be activated by fibrillar collagen, particularly types I and III, DDR1 is mostly activated by type I and IV collagens. In contrast with classical growth factor tyrosine kinase receptors which display a rapid and transient activation, DDR1 and DDR2 are unique in that they exhibit delayed and sustained receptor phosphorylation upon binding to collagen. Recent studies have reported differential expression and mutations of DDR1 and DDR2 in several cancer types and indicate clearly that these receptors have to be taken into account as new players in the different aspects of tumor progression, from non-malignant to highly malignant and invasive stages. This review will discuss the current knowledge on the role of DDR1 and DDR2 in malignant transformation, cell proliferation, epithelial to mesenchymal transition, migratory, and invasive processes, and finally the modulation of the response to chemotherapy. These new insights suggest that DDR1 and DDR2 are new potential targets in cancer therapy.

Integrative DNA methylation and gene expression analysis identifies discoidin domain receptor 1 association with idiopathic nonobstructive azoospermia

OBJECTIVE

To evaluate the association between promoter DNA methylation and discoidin domain receptor 1 (DDR1) gene expression in men with nonobstructive azoospermia (NOA).

DESIGN

Comparing fibroblasts cultured from testicular biopsies using a high resolution Infinium 450K methylation array.

SETTING

Basic research laboratory.

PATIENT(S)

Men with NOA (n = 16) and with normal spermatogenesis (n = 5).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Bisulfite clonal sequencing for validation and quantification of CpG methylation of DDR1; gene expression analysis of DDR1 with quantitative polymerase chain reaction and immunohistochemistry to validate the array results at mRNA and protein levels.

RESULT(S)

We validated promoter methylation, mRNA and protein levels of the CpG sites identified from array results. Differentially methylated CpG sites (∼20K) were identified using an F-test in the NOA samples. We identified 20 genes with >30% difference in DNA methylation within the promoter region of men with NOA and fertile controls. Of the aberrantly methylated genes, 10 were hypomethylated and 10 were hypermethylated genes. From the top 10 hypermethylated genes, six genes (MRI1, DCAF12L1, TMEM95, CECR2, DDR1, and NPHS2) were selected for validation because they were shown to be expressed in the testis. Of the six genes expressed in the fibroblasts cultured from testis, DDR1 showed an abnormal gene expression pattern. Three patients (19%) out of the 16 men with NOA for whom gene expression data were available had lower DDR1 expression levels (1.8x fold decrease) than the fertile men, whereas four (25%) men had higher expression levels (2x fold increase) of DDR1 compared with the levels in fertile men. Quantitative analysis by bisulfite clonal sequencing showed that one of the CpG sites (cg13329862) of DDR1 promoter was hypermethylated in NOA patients compared with fertile controls (53% vs. 15%). Immunohistochemical analysis suggests presence of DDR1 within cytoplasm of germ cells and peritubular connective tissue (in men with hypospermatogenesis) and decreased expression of the protein in men with Sertoli-cell only syndrome.

CONCLUSION(S)

Abnormal gene expression of DDR1 is associated with NOA. The functional relevance of aberrant methylation of DDR1 to expression of DDR1 in men with NOA warrants further investigation.

Genome-wide association study identifies candidate genes for male fertility traits in humans

Despite the fact that hundreds of genes are known to affect fertility in animal models, relatively little is known about genes that influence natural fertility in humans. To broadly survey genes contributing to variation in male fertility, we conducted a genome-wide association study (GWAS) of two fertility traits (family size and birth rate) in 269 married men who are members of a founder population of European descent that proscribes contraception and has large family sizes. Associations between ∼250,000 autosomal SNPs and the fertility traits were examined. A total of 41 SNPs with p ≤ 1 × 10(-4) for either trait were taken forward to a validation study of 123 ethnically diverse men from Chicago who had previously undergone semen analyses. Nine (22%) of the SNPs associated with reduced fertility in the GWAS were also associated with one or more of the ten measures of reduced sperm quantity and/or function, yielding 27 associations with p values < 0.05 and seven with p values < 0.01 in the validation study. On the basis of 5,000 permutations of our data, the probabilities of observing this many or more small p values were 0.0014 and 5.6 × 10(-4), respectively. Among the nine associated loci, outstanding candidates for male fertility genes include USP8, an essential deubiquitinating enzyme that has a role in acrosome assembly; UBD and EPSTI1, which have potential roles in innate immunity; and LRRC32, which encodes a latent transforming growth factor β (TGF-β) receptor on regulatory T cells. We suggest that mutations in these genes that are more severe may account for some of the unexplained infertility (or subfertility) in the general population.

Role of gonadotropin regulated testicular RNA helicase (GRTH/Ddx25) on polysomal associated mRNAs in mouse testis

Gonadotropin Regulated Testicular RNA Helicase (GRTH/Ddx25) is a testis-specific multifunctional RNA helicase and an essential post-transcriptional regulator of spermatogenesis. GRTH transports relevant mRNAs from nucleus to cytoplasmic sites of meiotic and haploid germ cells and associates with actively translating polyribosomes. It is also a negative regulator of steroidogenesis in Leydig cells. To obtain a genome-wide perspective of GRTH regulated genes, in particularly those associated with polyribosomes, microarray differential gene expression analysis was performed using polysome-bound RNA isolated from testes of wild type (WT) and GRTH KO mice. 792 genes among the entire mouse genome were found to be polysomal GRTH-linked in WT. Among these 186 were down-regulated and 7 up-regulated genes in GRTH null mice. A similar analysis was performed using total RNA extracted from purified germ cell populations to address GRTH action in individual target cells. The down-regulation of known genes concerned with spermatogenesis at polysomal sites in GRTH KO and their association with GRTH in WT coupled with early findings of minor or unchanged total mRNAs and abolition of their protein expression in KO underscore the relevance of GRTH in translation. Ingenuity pathway analysis predicted association of GRTH bound polysome genes with the ubiquitin-proteasome-heat shock protein signaling network pathway and NFκB/TP53/TGFB1 signaling networks were derived from the differentially expressed gene analysis. This study has revealed known and unexplored factors in the genome and regulatory pathways underlying GRTH action in male reproduction.

Migration inhibition of mammary epithelial cells by Syk is blocked in the presence of DDR1 receptors

The non-receptor tyrosine kinase Syk is a well-characterized hematopoietic signal transducer, which is also expressed in non-hematopoietic cells. In epithelial cells, the function of Syk is not wholly known. It interacts with the receptor tyrosine kinase DDR1 and is frequently lost from metastatic mammary tumors. Here, using genetic tracing, we demonstrate Syk expression in murine mammary epithelium, myoepithelium and skin epithelium, but not in intestinal or lung epithelia. Investigating possible functions of Syk, we found a substantial suppression of cell mobility that depended on Syk kinase activity in trans-well migration and wounding assays. Co-expression of DDR1 resulted in constitutive interaction and strong activation of Syk kinase. Most importantly, Syk-mediated migration inhibition was blocked in the presence of DDR1, while conversely DDR1 knockdown restored migration inhibition. Our study identifies Syk as a potent inhibitor of epithelial migration and describes a first functional consequence of the interaction with the collagen receptor DDR1.

Discoidin domain receptor 1: isoform expression and potential functions in cirrhotic human liver

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that binds and is activated by collagens. Transcriptional profiling of cirrhosis in human liver using a DNA array and quantitative PCR detected elevated mRNA expression of DDR1 compared with that in nondiseased liver. The present study characterized DDR1 expression in cirrhotic and nondiseased human liver and examined the cellular effects of DDR1 expression. mRNA expression of all five isoforms of DDR1 was detected in human liver, whereas DDR1a demonstrated differential expression in liver with hepatitis C virus and primary biliary cirrhosis compared with nondiseased liver. In addition, immunoblot analysis detected shed fragments of DDR1 more readily in cirrhotic liver than in nondiseased liver. Inasmuch as DDR1 is subject to protease-mediated cleavage after prolonged interaction with collagen, this differential expression may indicate more intense activation of DDR1 protein in cirrhotic compared with nondiseased liver. In situ hybridization and immunofluorescence localized intense DDR1 mRNA and protein expression to epithelial cells including hepatocytes at the portal-parenchymal interface and the luminal aspect of the biliary epithelium. Overexpression of DDR1a altered hepatocyte behavior including increased adhesion and less migration on extracelular matrix substrates. DDR1a regulated extracellular expression of matrix metalloproteinases 1 and 2. These data elucidate DDR1 function pertinent to cirrhosis and indicate the importance of epithelial cell-collagen interactions in chronic liver injury.

Discoidin Domain Receptor 1 on Bone Marrow–Derived Cells Promotes Macrophage Accumulation During Atherogenesis

Rationale : We described a critical role for the discoidin domain receptor (DDR)1 collagen receptor tyrosine kinase during atherosclerotic plaque development. Systemic deletion of Ddr1 in Ldlr −/− mice accelerated matrix accumulation and reduced plaque size and macrophage content. However, whether these effects reflected an independent role for macrophage DDR1 during atherogenesis remained unresolved.

Methods : In the present study, we performed sex-mismatched bone marrow transplantation using Ddr1 +/+ ; Ldlr −/− and Ddr1 −/− ; Ldlr −/− mice to investigate the role of macrophage DDR1 during atherogenesis. Chimeric mice with deficiency of DDR1 in bone marrow–derived cells ( Ddr1 −/−→+/+ ) or control chimeric mice that received Ddr1 +/+ ; Ldlr −/− marrow ( Ddr1 +/+→+/+ ) were fed an atherogenic diet for 12 weeks.

Results : We observed a 66% reduction in atherosclerosis in the descending aorta and a 44% reduction in plaque area in the aortic sinus in Ddr1 −/−→+/+ mice compared to Ddr1 +/+→+/+ mice. Furthermore, we observed a specific reduction in the number of donor-derived macrophages in Ddr1 −/−→+/+ plaques, suggesting that bone marrow deficiency of DDR1 attenuated atherogenesis by limiting macrophage accumulation in the plaque. We have also demonstrated that the effects of DDR1 on macrophage infiltration and accumulation can occur at the earliest stage of atherogenesis, the formation of the fatty streak. Deficiency of DDR1 limited the appearance of 5-bromodeoxyuridine–labeled monocytes/macrophages in the fatty streak and resulted in reduced lesion size in Ldlr −/− mice fed a high fat diet for 2 weeks. In vitro studies to investigate the mechanisms involved revealed that macrophages from Ddr1 −/− mice had decreased adhesion to type IV collagen and decreased chemotactic invasion of type IV collagen in response to monocyte chemoattractant protein-1.

Conclusions : Taken together, our data support an independent and critical role for DDR1 in macrophage accumulation at early and late stages of atherogenesis.

Discoidin Domain Receptor 1 ( Ddr1 ) Deletion Decreases Atherosclerosis by Accelerating Matrix Accumulation and Reducing Inflammation in Low-Density Lipoprotein Receptor–Deficient Mice

Collagens are abundant within the atherosclerotic plaque, where they contribute to lesion volume and mechanical stability and influence cell signaling. The discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase that binds to collagen, is expressed in blood vessels, but evidence for a functional role during atherogenesis is incomplete. In the present study, we generated Ddr1 +/+ ; Ldlr −/− and Ddr1 −/− ; Ldlr −/− mice and fed them an atherogenic diet for 12 or 24 weeks. Targeted deletion of Ddr1 resulted in a 50% to 60% reduction in atherosclerotic lesion area in the descending aorta at both 12 and 24 weeks. Ddr1 −/− ; Ldlr −/− plaques exhibited accelerated deposition of fibrillar collagen and elastin at 12 weeks compared with Ddr1 +/+ ; Ldlr −/− plaques. Expression analysis of laser microdissected lesions in vivo, and of Ddr1 −/− smooth muscle cells in vitro, revealed increased mRNA levels for procollagen α1(I) and α1(III) and tropoelastin, suggesting an enhancement of matrix synthesis in the absence of DDR1. Furthermore, whereas plaque smooth muscle cell content was unchanged, Ddr1 −/− ; Ldlr −/− plaques had a 49% decrease in macrophage content at 12 weeks, with a concomitant reduction of in situ gelatinolytic activity. Moreover, mRNA expression of both monocyte chemoattractant protein-1 and vascular cell adhesion molecule-1 was reduced in vivo, and Ddr1 −/− ; Ldlr −/− macrophages demonstrated impaired matrix metalloproteinase expression in vitro. These data suggest novel roles for DDR1 in macrophage recruitment and invasion during atherogenesis. In conclusion, our data support a role for DDR1 in the regulation of both inflammation and fibrosis early in plaque development. Deletion of DDR1 attenuated atherogenesis and resulted in the formation of matrix-rich plaques.

Identification of disulfide-linked dimers of the receptor tyrosine kinase DDR1

Discoidin domain receptor 1 (DDR1) is a transmembrane receptor tyrosine kinase activated by triple-helical collagen. So far six different isoforms of DDR1 have been described. Aberrant expression and signaling of DDR1 have been implicated in several human diseases linked to accelerated matrix degradation and remodeling, including tumor invasion, atherosclerosis, and lung fibrosis. Here we show that DDR1 exists as a disulfide-linked dimer in transfected as well as endogenously expressing cells. This dimer formation occurred irrespective of its kinase domain, as dimers were also found for the truncated DDR1d isoform. A deletion analysis of the extracellular domain showed that DDR1 mutants lacking the stalk region failed to form dimers, whereas deletion of the discoidin domain did not prevent dimerization. Point mutagenesis within the stalk region suggested that cysteines 303 and 348 are necessary for dimerization, collagen binding, and activation of kinase function. The identification of DDR1 dimers provides new insights into the molecular structure of receptor tyrosine kinases and suggests distinct signaling mechanisms of each receptor subfamily.