Identification of P311 as a potential gene regulating alveolar generation

Structural variants in the Epb41l4a locus: TAD disruption and Nrep gene misregulation as hypothetical drivers of neurodevelopmental outcomes

Structural variations are a pervasive feature of human genomes, and there is growing recognition of their role in disease development through their impact on spatial chromatin architecture. This understanding has led us to investigate the clinical significance of CNVs in noncoding regions that influence TAD structures. In this study, we focused on the Epb41l4a locus, which contains a highly conserved TAD boundary present in both human chromosome 5 and mouse chromosome 18, and its association with neurodevelopmental phenotypes. Analysis of human data from the DECIPHER database indicates that CNVs within this locus, including both deletions and duplications, are often observed alongside neurological abnormalities, such as dyslexia and intellectual disability, although there is not enough evidence of a direct correlation or causative relationship. To investigate these possible associations, we generated mouse models with deletion and inversion mutations at this locus and carried out RNA-seq analysis to elucidate gene expression changes. We found that modifications in the Epb41l4a TAD boundary led to dysregulation of the Nrep gene, which plays a crucial role in nervous system development. These findings underscore the potential pathogenicity of these CNVs and highlight the crucial role of spatial genome architecture in gene expression regulation.

The silencing of NREP aggravates OA cartilage damage through the TGF-β1/Smad2/3 pathway in chondrocytes

Background

Osteoarthritis (OA) is a common chronic degenerative joint disease. Due to the limited understanding of its complex pathological mechanism, there is currently no effective treatment that can alleviate or even reverse cartilage damage associated with OA. With improvement in public databases, researchers have successfully identified the key factors involved in the occurrence and development of OA through bioinformatics analysis. The aim of this study was to screen for the differentially expressed genes (DEGs) between the normal and OA cartilage through bioinformatics, and validate the function of the TGF-β1/Smad2/3 pathway-related neuron regeneration related protein (NREP) in the articular cartilage.

Methods

The DEGs between the cartilage tissues of OA patients and healthy controls were screened by bioinformatics, and functionally annotated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The expression levels of the DEG in human and murine OA cartilage was verified by reverse transcription-quantitative PCR (RT-qPCR), Western blotting and immunohistochemistry (IHC). RT-qPCR, Western-blotting, Cell Counting Kit-8(CCK8) and EdU assays were used to evaluate the effects of knocking down NREP in normal chondrocytes, and the molecular mechanisms were investigated by RT-qPCR, Western blotting and IHC.

Results

In this study, we identified NREP as a DEG in OA through bioinformatics analysis, and found that NREP was downregulated in the damaged articular cartilage of OA patients and mouse model with surgically-induced OA. In addition, knockdown of NREP in normal chondrocytes reduced their proliferative capacity, which is the pathological basis of OA. At the molecular level, knock-down of NREP inactivated the TGF-β1/Smad2/3 pathway, resulting in the downregulation of the anabolic markers Col2a1 and Sox9, and an increase in the expression of the catabolic markers MMP3 and MMP13.

Conclusion

NREP plays a key role in the progression of OA by regulating the TGF-β1/Smad2/3 pathway in chondrocytes, and warrants further study as a potential therapeutic target.

NREP contributes to development of NAFLD by regulating one-carbon metabolism in primary human hepatocytes

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. We recently discovered that neuronal regeneration-related protein (NREP/P311), an epigenetically regulated gene reprogrammed by parental metabolic syndrome, is downregulated in human NAFLD. To investigate the impact of NREP insufficiency, we used RNA-sequencing, lipidomics, and antibody microarrays on primary human hepatocytes. NREP knockdown induced transcriptomic remodeling that overlapped with key pathways impacted in human steatosis and steatohepatitis. Additionally, we observed enrichment of pathways involving phosphatidylinositol signaling and one-carbon metabolism. Lipidomics analyses also revealed an increase in cholesterol esters and triglycerides and decreased phosphatidylcholine levels in NREP-deficient hepatocytes. Signalomics identified calcium signaling as a potential mediator of NREP insufficiency's effects. Our results, together with the encouraging observation that several single nucleotide polymorphisms (SNPs) spanning the NREP locus are associated with metabolic traits, provide a strong rationale for targeting hepatic NREP to improve NAFLD pathophysiology.

P311 knockdown alleviates hyperoxia-induced injury by inactivating the Smad3 signaling pathway in type II alveolar epithelial cells

P311 is associated with alveolar formation and development. However, the role and possible mechanism of P311 in hyperoxia-induced injury in type II alveolar epithelial cells (AEC II) need to be elucidated. In our study, rat AEC II (RLE-6TN) were exposure to normoxia (21% O₂ and 5% CO₂) or hyperoxia (95% O₂ and 5% CO₂) for 24 h, followed by determination of P311 expression. After knockdown of P311 and hyperoxic treatment, cell viability, cell cycle progression, apoptosis and the Smad3 signaling pathway were examined. Rat AEC II were pretreated with SIS3 HCl for 4 h and then subjected to P311 overexpression plasmid transfection and hyperoxic exposure. Then, cell viability, apoptosis and the Smad3 signaling pathway were determined. The results showed that hyperoxic exposure significantly elevated P311 levels in rat AEC II. P311 knockdown increased cell viability, accelerated cell cycle progression and inhibited apoptosis, as well as suppression of the Smad3 signaling pathway in hyperoxia-exposed AEC II. Additionally, we found that P311 overexpression enhanced the effects of hyperoxia. Interestingly, SIS3 HCl incubation blocked the effects of P311 overexpression on rat AEC II function under hyperoxic condition, as evidenced by an increase in cell viability, and suppressions of apoptosis and the Smad3 signaling pathway. These results indicate that P311 knockdown may ameliorate hyperoxia-induced injury by inhibiting the Smad3 signaling pathway in rat AEC II. P311 may be a novel target for the treatment of hyperoxia-induced lung injury and even bronchopulmonary dysplasia (BPD).

P311 Facilitates the Angiogenesis and Wound Healing Function of MSCs by Increasing VEGF Production

As a potential clinical therapeutic cell for injured tissue repair, mesenchymal stem cells (MSCs) have attracted increasing attention. Enhancing the pro-healing function of MSCs has gradually become an essential topic in improving the clinical efficacy of MSCs. Recently, studies have shown that neuronal protein 3.1 (P311) plays a crucial role in promoting skin wound healing, suggesting P311 gene modification may improve the pro-healing function of MSCs. In this study, we demonstrated that increasing the in vivo expression of P311 could significantly enhance the ability of MSCs to lessen the number of inflammatory cells, increase the expression of IL10, reduce the levels of TNF-α and IFN-γ, increase collagen deposition, promote angiogenesis, and ultimately accelerate skin wound closure and improve the quality of wound healing. Importantly, we uncovered that P311 enhanced the pro-angiogenesis function of MSCs by increasing the production of vascular endothelial growth factor (VEGF) in vitro and in vivo. Mechanistically, we revealed that the mTOR signalling pathway was closely related to the regulation of P311 on VEGF production in MSCs. Together, our data displayed that P311 gene modification in MSCs augments their capabilities to promote skin wound closure, which might bring the dawn for its clinical application in the future.

[Effects of P311 on the angiogenesis ability of human microvascular endothelial cell 1 in vitro and its molecular mechanism]

Objective: To explore the effects of P311 on the angiogenesis ability of human microvascular endothelial cell 1 (HMEC-1) in vitro and the potential molecular mechanism. Methods: The experimental research method was used. HMEC-1 was collected and divided into P311 adenovirus group and empty adenovirus group according to the random number table (the same grouping method below), which were transfected correspondingly for 48 h. The cell proliferation activity was detected using the cell counting kit 8 on 1, 3, and 5 days of culture. The residual scratch area of cells at post scratch hour 6 and 11 was detected by scratch test, and the percentage of the residual scratch area was calculated. The blood vessel formation of cells at 8 h of culture was observed by angiogenesis experiment in vitro, and the number of nodes and total length of the tubular structure were measured. The protein expressions of vascular endothelial growth factor receptor 2 (VEGFR2), phosphorylated VEGFR2 (p-VEGFR2), extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphorylated ERK1/2 (p-ERK1/2) in cells were detected by Western blotting. HMEC-1 was collected and divided into P311 adenovirus+small interfering RNA (siRNA) negative control group, empty adenovirus+siRNA negative control group, P311 adenovirus+siRNA-VEGFR2 group, and empty adenovirus+siRNA-VEGFG2 group, which were treated correspondingly. The protein expressions of VEGFR2, p-VEGFR2, ERK1/2, and p-ERK1/2 in cells were detected by Western blotting at 24 h of transfection. The blood vessel formation of cells at 24 h of transfection was observed by angiogenesis experiment in vitro, and the number of nodes and total length of the tubular structure were measured. HMEC-1 was collected and divided into P311 adenovirus+dimethylsulfoxide (DMSO) group, empty adenovirus+DMSO group, P311 adenovirus+ERK1/2 inhibitor group, and empty adenovirus+ERK1/2 inhibitor group, which were treated correspondingly. The protein expressions of ERK1/2 and p-ERK1/2 in cells were detected by Western blotting at 2 h of treatment. The blood vessel formation of cells at 2 h of treatment was observed by angiogenesis experiment in vitro, and the number of nodes and total length of the tubular structure were measured. The sample number at each time point in each group was 6. Data were statistically analyzed with independent sample t test, analysis of variance for repeated measurement, one-way analysis of variance, and least significant difference test. Results: Compared with that of empty adenovirus group, the proliferation activity of cells in P311 adenovirus group did not show significant difference on 1, 3, and 5 days of culture (with t values of -0.23, -1.30, and -1.52, respectively, P>0.05). The residual scratch area percentages of cells in P311 adenovirus group were significantly reduced at post scratch hour 6 and 11 compared with those of empty adenovirus group (with t values of -2.47 and -2.62, respectively, P<0.05). At 8 h of culture, compared with those of empty adenovirus group, the number of nodes and total length of the tubular structure of cells in P311 adenovirus group were significantly increased (with t values of 4.49 and 4.78, respectively, P<0.01). At 48 h of transfection, compared with those of empty adenovirus group, the protein expressions of VEGFR2 and ERK1/2 of cells in P311 adenovirus group showed no obvious changes (P>0.05), and the protein expressions of p-VEGFR2 and p-ERK1/2 of cells in P311 adenovirus group were significantly increased (with t values of 17.27 and 16.08, P<0.01). At 24 h of transfection, the protein expressions of p-VEGFR2 and p-ERK1/2 of cells in P311 adenovirus+siRNA negative control group were significantly higher than those in empty adenovirus+siRNA negative control group (P<0.01). The protein expressions of VEGFR2, p-VEGFR2, and p-ERK1/2 of cells in P311 adenovirus+siRNA negative control group were significantly higher than those in P311 adenovirus+siRNA-VEGFR2 group (P<0.01). The protein expressions of VEGFR2 and p-ERK1/2 of cells in empty adenovirus+siRNA negative control group were significantly higher than those in empty adenovirus+siRNA-VEGFR2 group (P<0.05 or P<0.01). At 24 h of transfection, the number of nodes of the tubular structure in cells of P311 adenovirus+siRNA negative control group was 720±62, which was significantly more than 428±38 in empty adenovirus+siRNA negative control group and 364±57 in P311 adenovirus+siRNA-VEGFR2 group (with P values both <0.01). The total length of the tubular structure of cells in P311 adenovirus+siRNA negative control group was (21 241±1 139) μm, which was significantly longer than (17 005±1 156) μm in empty adenovirus+siRNA negative control group and (13 494±2 465) μm in P311 adenovirus+siRNA-VEGFR2 group (with P values both <0.01). The number of nodes of the tubular structure in cells of empty adenovirus+siRNA negative control group was significantly more than 310±75 in empty adenovirus+siRNA-VEGFR2 group (P<0.01), and the total length of the tubular structure of cells in empty adenovirus+siRNA negative control group was significantly longer than (11 600±2 776) μm in empty adenovirus+siRNA-VEGFR2 group (P<0.01). At 2 h of treatment, the protein expression of p-ERK1/2 of cells in P311 adenovirus+DMSO group was significantly higher than that in empty adenovirus+DMSO group and P311 adenovirus+ERK1/2 inhibitor group (with P values both <0.01), and the protein expression of p-ERK1/2 of cells in empty adenovirus+DMSO group was significantly higher than that in empty adenovirus+ERK1/2 inhibitor group (P<0.05). At 2 h of treatment, the number of nodes of the tubular structure in cells of P311 adenovirus+DMSO group was 726±72, which was significantly more than 421±39 in empty adenovirus+DMSO group and 365±41 in P311 adenovirus+ERK1/2 inhibitor group (with P values both <0.01). The total length of the tubular structure of cells in P311 adenovirus+DMSO group was (20 318±1 433) μm, which was significantly longer than (16 846±1 464) μm in empty adenovirus+DMSO group and (15 114±1 950) μm in P311 adenovirus+ERK1/2 inhibitor group (with P values both <0.01). The number of nodes of the tubular structure in cells of empty adenovirus+DMSO group was significantly more than 317±67 in empty adenovirus+ERK1/2 inhibitor group (P<0.01), and the total length of the tubular structure of cells in empty adenovirus+DMSO group was significantly longer than (13 188±2 306) μm in empty adenovirus+ERK1/2 inhibitor group (P<0.01). Conclusions: P311 can enhance the angiogenesis ability of HMEC-1 by activating the VEGFR2/ERK1/2 signaling pathway.

P311 regulates distal lung development via its interaction with several binding proteins

Little is known about the molecular mechanisms underlying alveolar development. P311, a putative neuronal protein originally identified for its high expression during neuronal development, has once been reported to play a potential role in distal lung generation. However, the function of this protein has been poorly understood so far. Hence, we carried out a yeast two-hybrid screen, combining with other protein-protein interaction experiments, to isolate several binding partners of P311 during lung development, which may help us explore its function. We report 7 proteins here, including Gal-1, Loxl-1 and SPARC, etc, that can interact with it. Most of them have similar spatio-temporal expression patterns to P311. In addition, it was also found that P311 could stimulate their expression indirectly in L929 mouse fibroblast. Besides, computational methods were applied to construct a P311 centered protein-protein interaction network during alveolarization, using the 7 binding partners and their protein interaction information provided by public data resources. By analyzing the structure and function of this network, the effects of P311 on lung development were further clarified and all of the bioinformatic predictions from the network could be validated by real experiments. We have found here that P311 can control lung redox events, extracellular matrix and cell cycle progression, which are all crucial to pulmonary morphogenesis. This gives us a novel thought to explore the mechanisms controlling alveolarization.

Parental metabolic syndrome epigenetically reprograms offspring hepatic lipid metabolism in mice

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide. Although gene-environment interactions have been implicated in the etiology of several disorders, the impact of paternal and/or maternal metabolic syndrome on the clinical phenotypes of offspring and the underlying genetic and epigenetic contributors of NAFLD have not been fully explored. To this end, we used the liver-specific insulin receptor knockout (LIRKO) mouse, a unique nondietary model manifesting 3 hallmarks that confer high risk for the development of NAFLD: hyperglycemia, insulin resistance, and dyslipidemia. We report that parental metabolic syndrome epigenetically reprograms members of the TGF-β family, including neuronal regeneration-related protein (NREP) and growth differentiation factor 15 (GDF15). NREP and GDF15 modulate the expression of several genes involved in the regulation of hepatic lipid metabolism. In particular, NREP downregulation increases the protein abundance of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and ATP-citrate lyase (ACLY) in a TGF-β receptor/PI3K/protein kinase B-dependent manner, to regulate hepatic acetyl-CoA and cholesterol synthesis. Reduced hepatic expression of NREP in patients with NAFLD and substantial correlations between low serum NREP levels and the presence of steatosis and nonalcoholic steatohepatitis highlight the clinical translational relevance of our findings in the context of recent preclinical trials implicating ACLY in NAFLD progression.

Molecular Mechanism of Mesenchyme Homeobox 1 in Transforming Growth Factor β1-Induced P311 Gene Transcription in Fibrosis

Organ fibrosis is characterized by excessive fibroblast, and extracellular matrix and the molecular basis are not fully elucidated. Recent studies have proven that P311, an 8-kDa conserved protein, could promote various organ fibrosis, such as skin, kidney, liver, and lung, partially through upregulating transforming growth factor β1 (TGF-β1) translation. However, the upstream regulators and mechanism of P311 gene regulation remain unclear, although we previously found that cytokines, hypoxia, and TGF-β1 could upregulate P311 transcription. Here, we aimed to elucidate the molecular mechanism of TGF-β1–induced P311 transcriptional regulation, focusing on mesenchyme homeobox 1 (Meox1). In this article, we identified the core promoter of P311 through bioinformatics analysis and luciferase reporter assays. Moreover, we demonstrated that Meox1, induced by TGF-β1, could bind to the promoter of P311 and promote its transcriptional activity. Furthermore, the effect of Meox1 on P311 transcriptional expression contributed to altered migration and proliferation in human dermal fibroblast cells. In conclusion, we identified Meox1 as a novel transcription factor of P311 gene, providing a new clue of the pathogenesis in fibrosis.

P311 Promotes Lung Fibrosis via Stimulation of Transforming Growth Factor-β1, -β2, and -β3 Translation

Interstitial lung fibrosis, a frequently idiopathic and fatal disease, has been linked to the increased expression of profibrotic transforming growth factor (TGF)-βs. P311 is an RNA-binding protein that stimulates TGF-β1, -β2, and -β3 translation in several cell types through its interaction with the eukaryotic translation initiation factor 3b. We report that P311 is switched on in the lungs of patients with idiopathic pulmonary fibrosis (IPF) and in the mouse model of bleomycin (BLM)-induced pulmonary fibrosis. To assess the in vivo role of P311 in lung fibrosis, BLM was instilled into the lungs of P311-knockout mice, in which fibrotic changes were significantly decreased in tandem with a reduction in TGF-β1, -β2, and -β3 concentration/activity compared with BLM-treated wild-type mice. Complementing these findings, forced P311 expression increased TGF-β concentration/activity in mouse and human lung fibroblasts, thereby leading to an activated phenotype with increased collagen production, as seen in IPF. Consistent with a specific effect of P311 on TGF-β translation, TGF-β1-, -β2-, and -β3-neutralizing antibodies downregulated P311-induced collagen production by lung fibroblasts. Furthermore, treatment of BLM-exposed P311 knockouts with recombinant TGF-β1, -β2, and -β3 induced pulmonary fibrosis to a degree similar to that found in BLM-treated wild-type mice. These studies demonstrate the essential function of P311 in TGF-β-mediated lung fibrosis. Targeting P311 could prove efficacious in ameliorating the severity of IPF while circumventing the development of autoimmune complications and toxicities associated with the use of global TGF-β inhibitors.

Reconstruction and Functional Annotation of P311 Protein-Protein Interaction Network Reveals Its New Functions

P311 is a highly conserved multifunctional protein. However, it does not belong to any established family of proteins, and its biological function has not been entirely determined. This study aims to reveal the unknown molecular and cellular function of P311. OCG (Overlapping Cluster Generator) is a clustering method used to partition a protein-protein network into overlapping clusters. Multifunctional proteins are at the intersection of relevant clusters. DAVID is an analytic tool used to extract biological meaning from a large protein list. Here we presented OD2 (OCG + DAVID + 2 human PPI datasets), a novel strategy to increase the likelihood to identify biological functions most pertinent to the multifunctional proteins. The principle of OD2 is that OCG prepares the protein lists from multifunctional protein relevant overlapping clusters, for a functional enrichment analysis by DAVID, and the similar functional enrichments, which occurs simultaneously when analyzing two human PPI datasets, are supposed to be the predicted functions. By applying OD2 to two reconstructed human PPI datasets, we supposed the function of the P311 in inflammatory responses, cell proliferation and coagulation, which were confirmed by the following biological experiments. Collectively, our study preliminarily found that P311 could play a role in inflammatory responses, cell proliferation and coagulation. Further studies are required to validate and elucidate the underlying mechanism.

P311, Friend, or Foe of Tissue Fibrosis?

P311 was first identified by the group of Studler et al. (1993) in the developing brain. In healthy, but mainly in pathological tissues, P311 is implicated in cell migration and proliferation. Furthermore, evidence in models of tissue fibrosis points to the colocalization with and the stimulation of transforming growth factor β1 by P311. This review provides a comprehensive overview on P311 and discusses its potential as an anti-fibrotic target.

Adenovirus-mediated P311 ameliorates renal fibrosis through inhibition of epithelial-mesenchymal transition via TGF-β1-Smad-ILK pathway in unilateral ureteral obstruction rats

Epithelial-mesenchymal transition (EMT) is a critical step and key factor during renal fibrosis. Preventing renal tubular EMT is important for delaying the progression of chronic kidney disease (CKD). P311, a highly conserved 8-kDa intracellular protein, has been indicated as an important factor in myofibroblast transformation and in the progression of fibrosis. However, the related studies on P311 on renal fibrosis are limited and the mechanisms of P311 in the progression of renal tubulointerstitial fibrosis remain largely unknown. In the present study, we examined the effect of P311 on transforming growth factor-β1 (TGF-β1)-mediated EMT in a rat model of unilateral ureteral occlusion (UUO) renal fibrosis. The recombinant adenovirus p311 (also called Ad-P311) was constructed and transferred it into UUO rats, the preventive effect and possible mechanism of P311 on TGF-β1-mediated EMT were explored. The UUO model was established successfully and Ad-P311 was administered into UUO rats each week for 4 weeks, then the serum levels of Cr, blood urea nitrogen (BUN) and albumin (ALB) were evaluated. H&E staining and Masson staining were performed to observe the pathological changes of kidneys. Immunohistochemical staining and western blot analysis were used to examine the EMT markers [E-cadherin and α-smooth muscle actin (α-SMA)], and signal transducers (p-Smad2/3 and Smad7). Integrin linked kinase (ILK) as a keyintracellular mediator that controls TGF-β1-mediated-EMT was also assayed by western blot analysis. The results showed that P311 could alleviate renal tubular damage and interstitial fibrosis improving Cr, BUN and ALB serum levels in UUO kidneys. Furthermore, P311 attenuated TGF-β1-mediated EMT through Smad-ILK signaling pathway with an increase in α-SMA, pSmad2/3 and ILK expression, and a decrease in E-cadherin and Smad7 expression in UUO kidneys. In conclusion, P311 may be involved in the pathogenesis of renal fibrosis by blocking TGF-β1-mediated EMT via TGF-β1-Smad-ILK pathway in UUO kidneys. P311 may be a novel target for the control of renal fibrosis and the progression of CKD.

Shenqi detoxification granule combined with P311 inhibits epithelial-mesenchymal transition in renal fibrosis via TGF-β1-Smad-ILK pathway

Shenqi detoxification granule (SDG), a traditional Chinese herbal formula, has been shown to have nephroprotective and anti-fibrotic activities in patients with chronic kidney disease (CKD). However, its mechanisms in renal fibrosis and the progression of CKD remain largely unknown. P311, a highly conserved 8-kDa intracellular protein, plays a key role in renal fibrosis by regulating epithelial-mesenchymal transition (EMT). Previously, we found P311 might be involved in the pathogenesis of renal fibrosis by inhibiting EMT via the TGF-β1-Smad-ILK pathway. We also found SDG combined with P311 could ameliorate renal fibrosis by regulating the expression of EMT markers. Here we further examined the effect and mechanism of SDG combined with P311 on TGF-β1-mediated EMT in a rat model of unilateral ureteral occlusion (UUO) renal fibrosis. After establishment of the UUO model successfully, the rats were gavaged with SDG daily and/or injected with recombinant adenovirus p311 (also called Ad-P311) through the tail vein each week for 4 weeks. Serum creatinine (Cr), blood urea nitrogen (BUN) and albumin (ALB) levels were tested to observe renal function, and hematoxylin eosin (HE) and Masson staining were performed to observe kidney histopathology. Furthermore, the expression of EMT markers (E-cadherin and α-smooth muscle actin (α-SMA)) and EMT-related molecules TGF-β1, pSmad2/3, Smad7 and ILK were observed using immunohistochemical staining and Western blot analysis. Treatment with SDG and P311 improved renal function and histopathological abnormalities, as well as reversing the changes of EMT markers and EMT-related molecules, which indicated SDG combined with P311 could attenuate renal fibrosis in UUO rats, and the underlying mechanism might involve TGF-β1-mediated EMT and the TGF-β1-Smad-ILK signaling pathway. Therefore, SDG might be a novel alternative therapy for treating renal fibrosis and delaying the progression of CKD. Furthermore, SDG combined with P311 might have a synergistic effect on attenuating renal fibrosis.

P311 Deficiency Leads to Attenuated Angiogenesis in Cutaneous Wound Healing

P311 was identified to markedly promote cutaneous wound healing by our group. Angiogenesis plays a key role in wound healing. In this study, we sought to define the role of P311 in skin wound angiogenesis. It was noted that P311 was expressed in endothelial cells in the dermis of murine and human skin wounds. The expression of P311 was confirmed in cultured murine dermal microvascular endothelial cells (mDMECs). Moreover, it was found that knockout of P311 could attenuate the formation of tubes and motility of mDMECs significantly in vitro. In the subcutaneous Matrigel implant model, the angiogenesis was reduced significantly in P311 knockout mice. In addition, wound healing was delayed in P311 knockout mice compared with that in the wild type. Granulation tissue formation during the defective wound healing showed thinner and blood vessel numbers in wound areas in P311 knockout mice were decreased significantly. A reduction in VEGF and TGFβ1 was also found in P311 KO mice wounds, which implied that P311 may modulate the exprssion of VEGF and TGFβ1 in wound healing. Together, our findings suggest that P311 plays an important role in angiogenesis in wound healing.

Neuronal Protein 3.1 Deficiency Leads to Reduced Cutaneous Scar Collagen Deposition and Tensile Strength due to Impaired Transforming Growth Factor-β1 to -β3 Translation

Neuronal protein 3.1 (P311), a conserved RNA-binding protein, represents the first documented protein known to stimulate transforming growth factor (TGF)-β1 to -β3 translation in vitro and in vivo. Because TGF-βs play critical roles in fibrogenesis, we initiated efforts to define the role of P311 in skin scar formation. Here, we show that P311 is up-regulated in skin wounds and in normal and hypertrophic scars. Genetic ablation of p311 resulted in a significant decrease in skin scar collagen deposition. Lentiviral transfer of P311 corrected the deficits, whereas down-regulation of P311 levels by lentiviral RNA interference reproduced the deficits seen in P311^-/- mice. The decrease in collagen deposition resulted in scars with reduced stiffness but also reduced scar tensile strength. In vitro studies using murine and human dermal fibroblasts showed that P311 stimulated TGF-β1 to -β3 translation, a process that involved eukaryotic translation initiation factor 3 subunit b as a P311 binding partner. This resulted in increased TGF-β levels/activity and increased collagen production. In addition, P311 induced dermal fibroblast activation and proliferation. Finally, exogenous TGF-β1 to -β3, each restituted the normal scar phenotype. These studies demonstrate that P311 is required for the production of normal cutaneous scars and place P311 immediately up-stream of TGF-βs in the process of fibrogenesis. Conditions that decrease P311 levels could result in less tensile scars, which could potentially lead to higher incidence of dehiscence after surgery.

Adenovirus-mediated P311 inhibits TGF-β1-induced epithelial-mesenchymal transition in NRK-52E cells via TGF-β1-Smad-ILK pathway

P311, a highly conserved 8-kDa intracellular protein, has been indicated as an important factor in myofibroblast transformation and in the progression of fibrosis. In the present study, we constructed a recombinant adenovirus vector of p311 (called Ad-P311) and transferred it into rat renal proximal tubular epithelial cells (NRK-52E) to explore the effect of P311 on epithelial-mesenchymal transition (EMT) of NRK-52E cells induced by TGF-β1 and to elucidate its underlying mechanism against EMT. After successfully construction of Ad-P311 and transfer into NRK-52E cells, the proliferation and growth of P311-expressing cells was detected by MTT assay. TGF-β1 was used to induce NRK-52E cells and Western blot analysis was used to examine the EMT markers (E-cadherin and α-smooth muscle actin (α-SMA)), signal transducers (p-Smad2/3 and Smad7). Integrin Linked Kinase (ILK) as a key intracellular mediator that controls TGF-β1-induced-EMT was also assayed by Western blot analysis. The results showed that P311 transfection could significantly inhibit the proliferation and growth of TGF-β1 induced NRK-52E cells. The results also showed that TGF-β1 could induce EMT in NRK-52E cells through Smad-ILK signaling pathway with an increase in α-SMA, pSmad2/3 and ILK expression, and a decrease in E-cadherin and Smad7 expression. However, P311 efficiently blocked Smad-ILK pathway activation and attenuated all these EMT changes induced by TGF-β1. These findings suggest that P311 might be involved in the pathogenesis of renal fibrosis by inhibiting the EMT process via TGF-β1-Smad-ILK pathway. P311 might be a novel target for the control of renal fibrosis and the progression of CKD.

P311 promotes renal fibrosis via TGFβ1/Smad signaling

P311, a gene that was identified in 1993, has been found to have diverse biological functions in processes such as cell proliferation, migration and differentiation. However, its role in fibrosis is unknown. We previously observed that P311 is highly expressed in skin hypertrophic scars. In this study, P311 over-expression was detected in a subset of tubular epithelial cells in clinical biopsy specimens of renal fibrosis; this over-expression, was found concurrent with α-smooth muscle actin (α-SMA) and transforming growth factor beta1 (TGFβ1) expression. Subsequently, these results were verified in a mouse experimental renal fibrosis model induced by unilateral ureteral obstruction. The interstitial deposition of collagen, α-SMA and TGF-β1 expression, and macrophage infiltration were dramatically decreased when P311 was knocked out. Moreover, TGFβ/Smad signaling had a critical effect on the promotion of renal fibrosis by P311. In conclusion, this study demonstrate that P311 plays a key role in renal fibrosis via TGFβ1/Smad signaling, which could be a novel target for the management of renal fibrosis.

P311 modulates hepatic stellate cells migration

BACKGROUND & AIMS

Liver fibrosis is induced by the accumulation of extracellular matrix, deposited mainly by activated hepatic stellate cells (HSCs). One key characteristic of stellate cell activation is the directional migration to the site of injury during the wound-healing process. P311 is a protein that has been shown to play a role in migration and we aimed to study a possible role for this protein during stellate cell migration.

METHODS

Mouse stellate cells were isolated and cultured in vitro to investigate P311 protein and gene expression during HSC activation by immunocytochemistry and RT-qPCR respectively. Expression of P311 during in vivo activation was evaluated in CCl4 and bile duct ligation-induced liver fibrosis. Production of reactive oxygen species was determined using the fluorescent probe DCFH-DA. By siRNA-mediated knockdown of P311, we investigated a possible effect on proliferation by incorporation of EdU and on migration by Boyden chamber assays.

RESULTS

P311 gene expression was increased during both in vitro and in vivo activation of HSCs. siRNA-mediated knockdown led to a decrease in reactive oxygen production and cell proliferation. Migration induced by different chemokines, such as PDGF-bb and MCP-1 was inhibited by knockdown of P311.

CONCLUSIONS

P311 is central to reactive oxygen species-mediated HSC migration induced by different chemokines.

Novel RNA-binding protein P311 binds eukaryotic translation initiation factor 3 subunit b (eIF3b) to promote translation of transforming growth factor β1-3 (TGF-β1-3)

P311, a conserved 8-kDa intracellular protein expressed in brain, smooth muscle, regenerating tissues, and malignant glioblastomas, represents the first documented stimulator of TGF-β1-3 translation in vitro and in vivo. Here we initiated efforts to define the mechanism underlying P311 function. PONDR® (Predictor Of Naturally Disordered Regions) analysis suggested and CD confirmed that P311 is an intrinsically disordered protein, therefore requiring an interacting partner to acquire tertiary structure and function. Immunoprecipitation coupled with mass spectroscopy identified eIF3 subunit b (eIF3b) as a novel P311 binding partner. Immunohistochemical colocalization, GST pulldown, and surface plasmon resonance studies revealed that P311-eIF3b interaction is direct and has a Kd of 1.26 μm. Binding sites were mapped to the non-canonical RNA recognition motif of eIF3b and a central 11-amino acid-long region of P311, here referred to as eIF3b binding motif. Disruption of P311-eIF3b binding inhibited translation of TGF-β1, 2, and 3, as indicated by luciferase reporter assays, polysome fractionation studies, and Western blot analysis. RNA precipitation assays after UV cross-linking and RNA-protein EMSA demonstrated that P311 binds directly to TGF-β 5'UTRs mRNAs through a previously unidentified RNA recognition motif-like motif. Our results demonstrate that P311 is a novel RNA-binding protein that, by interacting with TGF-βs 5'UTRs and eIF3b, stimulates the translation of TGF-β1, 2, and 3.

Blood pressure homeostasis is maintained by a P311-TGF-β axis

P311 is an 8-kDa intracellular protein that is highly conserved across species and is expressed in the nervous system as well as in vascular and visceral smooth muscle cells. P311-null (P311-/-) mice display learning and memory defects, but alterations in their vasculature have not been previously described. Here we report that P311-/- mice are markedly hypotensive with accompanying defects in vascular tone and VSMC contractility. Functional abnormalities in P311-/- mice resulted from decreased total and active levels of TGF-β1, TGF-β2, and TGF-β3 that arise as a specific consequence of decreased translation. Vascular hypofunctionality was fully rescued in vitro and in vivo by exogenous TGF-β1-TGF-β3. Conversely, P311-transgenic (P311(TG)) mice had elevated levels of TGF-β1-TGF-β3 and subsequent hypertension. Consistent with findings attained in mouse models, arteries recovered from hypertensive human patients displayed increased P311 expression. Thus, we identified P311 as the first protein known to modulate TGF-β translation and the first pan-regulator of TGF-β expression under steady-state conditions. Together, our findings point to P311 as a critical blood pressure regulator and establish a potential link between P311 expression and the development of hypertensive disease.

Ozone exposure during the early postnatal period alters the timing and pattern of alveolar growth and development in nonhuman primates

Exposure to oxidant air pollutants in early childhood, with ozone as the key oxidant, has been linked to significant decrements in pulmonary function in young adults and exacerbation of airway remodeling in asthma. Development of lung parenchyma in rhesus monkeys is rapid during the first 2 years of life (comparable to the first 6 years in humans). Our hypothesis is that ozone inhalation during infancy alters alveolar morphogenesis. We exposed infant rhesus monkeys biweekly to 5, 8 hr/day, cycles of 0.5 ppm ozone with or without house dust mite allergen from 1 to 3 or 1 to 6 months of age. Monkeys were necropsied at 3 and 6 months of age. A morphometric approach was used to quantify changes in alveolar volume and number, the distribution of alveolar size, and capillary surface density per alveolar septa. Quantitative real time PCR was used to measure the relative difference in gene expression over time. Monkeys exposed to ozone alone or ozone combined with allergen had statistically larger alveoli that were less in number at 3 months of age. Alveolar capillary surface density was also decreased in the ozone exposed groups at 3 months of age. At 6 months of age, the alveolar number was similar between treatment groups and was associated with a significant rise in alveolar number from 3 to 6 months of age in the ozone exposed groups. This increase in alveolar number was not associated with any significant increase in microvascular growth as measured by morphometry or changes in angiogenic gene expression. Inhalation of ozone during infancy alters the appearance and timing of alveolar growth and maturation. Understanding the mechanism involved with this altered alveolar growth may provide insight into the parenchymal injury and repair process that is involved with chronic lung diseases such as severe asthma and COPD.

MiR-134 functions as a regulator of cell proliferation, apoptosis, and migration involving lung septation

MicroRNAs (miRNAs) are 21-25 nt long non-coding RNA that modulate various biological processes, including developmental timing via regulating the expression of their target genes. One critical determinant of normal postnatal lung architecture is septation, and there are many miRNAs involved in the development process. miR-134 is reported as a powerful inducer of pluripotent stem cell differentiation, and we have found that miR-134 is strongly downregulated during mice lung septation (from postnatal Day 2 to postnatal Day 21). Further cell function experiments have revealed that over-expression of miR-134 in A549 and Calu-3 cells can promote cell proliferation and inhibit cell apoptosis and migration abilities in vitro, and the down-expression of miR-134 in cells can act in the opposite way, which indicate that miR-134 is associated with lung septation. This study provides a basis for further investigation of its function in lung development.

PSMB2 and RPL32 are suitable denominators to normalize gene expression profiles in bronchoalveolar cells

BACKGROUND

For accuracy of quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), normalisation with suitable reference genes is required. To date, no reference genes have been validated for expression studies of bronchoalveolar (BAL) cells. The aims of this study were to identify gene(s) with stable mRNA expression in BAL cells irrespective of gender, smoking, BAL cellular composition, lung pathology, treatment; and to assess the influence of reference genes on target gene expression data.

RESULTS

The mRNA expression of ten housekeeping genes (ACTB, ARF1, CANX, G6PD, GAPDH, GPS1, GNB2L1, PSMB2, PSMD2, RPL32) was investigated by qRT-PCR in BAL cells from 71 subjects across a spectrum of lung diseases. The analyses were validated in an independent BAL cohort from 63 sarcoidosis patients and 17 control subjects. A second derivative method was used to calculate expression values (CTt); an equivalence test, applets BestKeeper, geNorm and NormFinder were applied to investigate gene expression stability. Of the investigated genes, PSMB2 (CTt +/- SD, 23.66 +/- 0.86) and RPL32 (18.65 +/- 0.92) were the most stable; both were constantly expressed in BAL samples from parallel investigated cohorts irrespective of evaluated variables. Finally, to demonstrate effect of traditional (ACTB/GAPDH) and novel (PSMB2/RPL32) reference genes as denominators, expression of two cytokines known associated with sarcoidosis was investigated in sarcoid BAL cells. While normalization with PSMB2/RPL32 resulted in elevated IFNG mRNA expression (p = 0.004); no change was observed using GAPDH/ACTB (p > 0.05). CCL2 mRNA up-regulation was observed only when PSMB2/RPL32 were used as denominators (p < 0.03).

CONCLUSION

PSMB2 and RPL32 are, therefore, suitable reference genes to normalize qRT-PCR in BAL cells in sarcoidosis, and other interstitial lung disease.

P311 functions in an alternative pathway of lipid accumulation that is induced by retinoic acid

Lipid droplets are complex and dynamic intracellular organelles that have an essential role in cholesterol and lipid homeostasis, and profoundly affect cellular structure and function. Variations in lipid-droplet composition exist between different cell types, but whether there are differences in the mechanisms of lipid-droplet accumulation remains to be elucidated. Here, we report that P311, previously identified to have a function in neuronal regeneration and a potential role in distal lung generation, regulates lipid droplet accumulation. P311 upregulates several classes of genes associated with lipid synthesis, significantly increases intracellular cholesterol and triglyceride levels, and increases intracellular lipid droplets. Interestingly, P311 expression is not necessary for lipogenesis in the well-established NIH3T3-L1 cell model of adipogenic differentiation. Instead, we demonstrate a novel role for P311 in an alternative pathway of lipid-droplet accumulation that is induced by the regeneration-inducing molecule retinoic acid.

Disease-specific gene expression profiling in multiple models of lung disease

RATIONALE

Microarray technology is widely employed for studying the molecular mechanisms underlying complex diseases. However, analyses of individual diseases or models of diseases frequently yield extensive lists of differentially expressed genes with uncertain relationships to disease pathogenesis.

OBJECTIVES

To compare gene expression changes in a heterogeneous set of lung disease models in order to identify common gene expression changes seen in diverse forms of lung pathology, as well as relatively small subsets of genes likely to be involved in specific pathophysiological processes.

METHODS

We profiled lung gene expression in 12 mouse models of infection, allergy, and lung injury. A linear model was used to estimate transcript expression changes for each model, and hierarchical clustering was used to compare expression patterns between models. Selected expression changes were verified by quantitative polymerase chain reaction.

MEASUREMENTS AND MAIN RESULTS

A total of 24 transcripts, including many involved in inflammation and immune activation, were differentially expressed in a substantial majority (9 or more) of the models. Expression patterns distinguished three groups of models: (1) bacterial infection (n = 5), with changes in 89 transcripts, including many related to nuclear factor-kappaB signaling, cytokines, chemokines, and their receptors; (2) bleomycin-induced diseases (n = 2), with changes in 53 transcripts, including many related to matrix remodeling and Wnt signaling; and (3) T helper cell type 2 (allergic) inflammation (n = 5), with changes in 26 transcripts, including many encoding epithelial secreted molecules, ion channels, and transporters.

CONCLUSIONS

This multimodel dataset highlights novel genes likely involved in various pathophysiological processes and will be a valuable resource for the investigation of molecular mechanisms underlying lung disease pathogenesis.

Matrix metalloproteinases in lung: multiple, multifarious, and multifaceted

The matrix metalloproteinases (MMPs), a family of 25 secreted and cell surface-bound neutral proteinases, process a large array of extracellular and cell surface proteins under normal and pathological conditions. MMPs play critical roles in lung organogenesis, but their expression, for the most part, is downregulated after generation of the alveoli. Our knowledge about the resurgence of the MMPs that occurs in most inflammatory diseases of the lung is rapidly expanding. Although not all members of the MMP family are found within the lung tissue, many are upregulated during the acute and chronic phases of these diseases. Furthermore, potential MMP targets in the lung include all structural proteins in the extracellular matrix (ECM), cell adhesion molecules, growth factors, cytokines, and chemokines. However, what is less known is the role of MMP proteolysis in modulating the function of these substrates in vivo. Because of their multiplicity and substantial substrate overlap, MMPs are thought to have redundant functions. However, as we explore in this review, such redundancy most likely evolved as a necessary compensatory mechanism given the critical regulatory importance of MMPs. While inhibition of MMPs has been proposed as a therapeutic option in a variety of inflammatory lung conditions, a complete understanding of the biology of these complex enzymes is needed before we can reasonably consider them as therapeutic targets.