The role of progranulin (PGRN) in the modulation of anti-inflammatory response in asthma

Progranulin Plays a Protective Role in Pneumococcal Meningitis by Inhibiting Pyroptosis

OBJECTIVE

Pneumococcal meningitis is a serious infectious disease with a high mortality rate and a global presence, and survivors have different degrees of neurological sequelae as a consequence of the host response to the infection. Progranulin (PGRN) is a multifunctional autocrine growth factor that is also a major immunoregulator. We want to investigate the role for PGRN in Pneumococcal meningitis in vivo and in vitro.

METHOD

Mouse and cell models were established to explore the protective effect and mechanism of PGRN against pneumococcal meningitis.

RESULTS

Progranulin plays a protective role in pneumococcal meningitis by inhibiting pyroptosis. Pyroptosis resulted from exposure of BV-2 cells to the bacterium and this was confirmed in the in vivo model. Administration of the NLRP3 inflammasome inhibitor MCC950 to mice prior to infection inhibited pyroptosis and protected PGRN -/- mice and BV-2 cell model from meningitis.

CONCLUSION

This study implicates a protective role for PGRN in pneumococcal meningitis by inhibiting pyroptosis, indicating that PGRN may have therapeutic potential.

PGRN Inhibits Early B-cell Activation and IgE Production Through the IFITM3-STAT1 Signaling Pathway in Asthma

Progranulin (PGRN) plays a critical role in bronchial asthma and the function of various immune cells. However, the mechanisms by which PGRN influences B-cell receptor (BCR) signaling and immunoglobulin E(IgE) production are not fully understood. The study aimed to elucidate the molecular mechanisms through which PGRN affects BCR signaling, B-cell differentiation, and IgE production. A PGRN knockout mouse model, along with techniques including flow cytometry, the creation of a bone marrow chimeric mouse model, total internal reflection fluorescence (TIRF), and Western blot (WB) analysis is employed, to investigate the link between PGRN and various aspects of B-cell biology. It is discovered that the absence of PGRN in mice alters peripheral B-cell subpopulations, promotes IgE class switching in a cell-intrinsic manner, and affects B-cell subpopulations. Additionally, PGRN modulates B-cell functions by regulating BCR signaling pathways, metabolic processes, and the actin cytoskeleton during early B-cell activation. Significantly, PGRN deficiency results in diminished production of NP-specific antibodies. Moreover, it is found that PGRN inhibits B-cell activation and IgE production through the PGRN-IFITM3-STAT1 signaling pathway. The findings provide new strategies for the targeted treatment of bronchial asthma, highlighting the crucial role of PGRN in B-cell signaling and IgE production.

Progranulin: A promising biomarker and therapeutic target for fibrotic diseases

Progranulin (PGRN), a multifunctional growth factor-like protein expressed by a variety of cell types, serves an important function in the physiologic and pathologic processes of fibrotic diseases, including wound healing and the inflammatory response. PGRN was discovered to inhibit pro-inflammation effect by competing with tumor necrosis factor-alpha (TNF-α) binding to TNF receptors. Notably, excessive tissue repair in the development of inflammation causes tissue fibrosis. Previous investigations have indicated the significance of PGRN in regulating inflammatory responses. Recently, multiple studies have shown that PGRN was linked to fibrogenesis, and was considered to monitor the formation of fibrosis in multiple organs, including liver, cardiovascular, lung and skin. This paper is a comprehensive review summarizing our current knowledge of PGRN, from its discovery to the role in fibrosis. This is followed by an in-depth look at the characteristics of PGRN, consisting of its structure, basic function and intracellular signaling. Finally, we will discuss the potential of PGRN in the diagnosis and treatment of fibrosis.

Progranulin regulates the development and function of NKT2 cells through EZH2 and PLZF

T helper 2 (Th2) cytokine production by invariant natural killer T (iNKT) cells is involved in the development of asthma, but the regulation of Th2 cytokines in iNKT cells remains unknown. Although it is known that progranulin (PGRN) induces the production of Th2 cytokines in iNKT cells in vivo, the underlying mechanism is not clear. This study aims to investigate the role of PGRN in iNKT cells. The effects of PGRN on the differentiation of iNKT cells was detected by flow cytometry. Then stimulation of iNKT cells and airway resistance were carried out to evaluate the function of PGRN on iNKT cells. Furthermore, the mechanisms of PGRN in regulating iNKT cells was investigated by RT-PCR, WB, confocal and luciferase reporter assays. The absolute number of iNKT cells decreased in PGRN KO mice despite an increase in the percentage of iNKT cells. Furthermore, analyzing the subsets of iNKT cells, we found that NKT2 cells and their IL-4 production were reduced. Mechanistically, the decrease in NKT2 cells in the PGRN KO mice was caused by increased expression of enhancer of zeste homolog 2 (EZH2), that in turn caused increased degradation and altered nuclear localization of PLZF. Interestingly, PGRN signaling decreased expression of EZH2 and treatment of the PGRN KO mice with the EZH2 specific inhibitor GSK343 rescued the defect in NKT2 differentiation, IL-4 generation, and PLZF expression. Altogether, We have revealed a new pathway (PGRN-EZH2-PLZF), which regulates the Th2 responses of iNKT cells and provides a potentially new target for asthma treatment.

Role of adipokines in embryo implantation

Embryo implantation is a complex process in which multiple molecules acting together under strict regulation. Studies showed the production of various adipokines and their receptors in the embryo and uterus, where they can influence the maternal-fetal transmission of metabolites and embryo implantation. Therefore, these cytokines have opened a novel area of study in the field of embryo-maternal crosstalk during early pregnancy. In this respect, the involvement of adipokines has been widely reported in the regulation of both physiological and pathological aspects of the implantation process. However, the information about the role of some recently identified adipokines is limited. This review aims to highlight the role of various adipokines in embryo-maternal interactions, endometrial receptivity, and embryo implantation, as well as the underlying molecular mechanisms.

Progranulin Protects Against Airway Remodeling Through the Modulation of Autophagy via HMGB1 Suppression in House Dust Mite-Induced Chronic Asthma

Purpose

Airway remodeling is an important feature of chronic asthma, and yet there are few effective therapeutic strategies. Progranulin (PGRN) has been shown to have lung protective functions, but the role of PGRN in asthmatic airway remodeling is unclear. We aim to explore the protective potential of PGRN on house dust mite (HDM)-induced airway remodeling and the underlying mechanisms.

Methods

In this study, a murine model of chronic asthma was established by HDM sensitization and challenge. Recombinant PGRN was intranasally administrated to mice during the phase of HDM challenge. TGF-β1-treated human airway epithelial BEAS-2B cells were utilized to explore the effect of PGRN on airway epithelia exposed to profibrotic conditions and molecular mechanisms.

Results

We found that PGRN treatment attenuated HDM-induced airway remodeling, as evidenced by the suppression of collagen accumulation, mucus overproduction and airway smooth muscle synthesis in HDM-challenged asthmatic mice lungs. Meanwhile, PGRN also reversed the increased levels of autophagy markers and autophagosomes in airway epithelia under mimic asthmatic conditions, thereby controlling the fibrotic process in vivo and in vitro. Specifically, overexpressed HMGB1 and the subsequent RAGE/MAPKs signaling activation due to HDM exposure were abrogated in PGRN-treated asthmatic mice. Furthermore, knockdown of HMGB1 expression significantly restrained the fibrosis formation in TGF-β1-induced airway epithelia accompanied by the downregulation of autophagic activity. However, enhancement of extracellular HMGB1 levels blunted the inhibition of autophagic flux by PGRN in airway epithelia, thereby resulting in the augmentation of collagen synthesis and fibrosis.

Conclusion

Taken together, our data revealed that PGRN protected against asthmatic airway remodeling by negatively regulating autophagy via HMGB1 suppression, which might provide new insights into the therapeutic options for HDM-induced chronic asthma.

Progranulin induces immune escape in breast cancer via up-regulating PD-L1 expression on tumor-associated macrophages (TAMs) and promoting CD8+ T cell exclusion

Background

Progranulin (PGRN), as a multifunctional growth factor, is overexpressed in multiple tumors, but the role of PGRN on tumor immunity is still unclear. Here, we studied the effect of PGRN on breast cancer tumor immunity and its possible molecular mechanism.

Methods

The changes of macrophage phenotypes after PGRN treatment were detected by western blot, quantitative polymerase chain reaction (PCR) and flow cytometry. Western blot was used to study the signal molecular mechanism of PGRN regulating this process. The number and localization of immune cells in Wild-type (WT) and PGRN^−/− breast cancer tissues were analyzed by immunohistochemical staining and immunofluorescence techniques. The activation and proliferation of CD8⁺ T cells were measured by flow cytometry.

Results

After being treated with PGRN, the expressions of M2 markers and programmed death ligand 1 (PD-L1) on macrophages increased significantly. Signal transducer and activator of transcription 3 (STAT3) signaling pathway inhibitor Stattic significantly inhibited the expression of PD-L1 and M2 related markers induced by PGRN. In WT group, CD8 were co-localized with macrophages and PD-L1, but not tumor cells. The number of immune cells in PGRN^−/− breast cancer tissue increased, and their infiltration into tumor parenchyma was also enhanced. Moreover, in the co-culture system, WT peritoneal macrophages not only reduced the ratio of activated CD8⁺ T cells but also reduced the proportion of proliferating CD8⁺ T cells. The addition of programmed death receptor 1 (PD-1) and PD-L1 neutralizing antibodies effectively reversed this effect and restored the immune function of CD8⁺ T cells.

Conclusion

These results demonstrate that PGRN promotes M2 polarization and PD-L1 expression by activating the STAT3 signaling pathway. Furthermore, through PD-1/PD-L1 interaction, PGRN can promote the breast tumor immune escape. Our research may provide new ideas and targets for clinical breast cancer immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01786-6.

Folding of Truncated Granulin Peptides

Granulins are a family of unique protein growth factors which are found in a range of species and have several bioactivities that include cell proliferation and wound healing. They typically contain six disulfide bonds, but the sequences, structures and bioactivities vary significantly. We have previously shown that an N-terminally truncated version of a granulin from the human liver fluke, Opisthorchis viverrini, can fold independently into a “mini-granulin” structure and has potent wound healing properties in vivo. The incorporation of a non-native third disulfide bond, with respect to the full-length granulin module, was critical for the formation of regular secondary structure in the liver fluke derived peptide. By contrast, this third disulfide bond is not required for a carp granulin-1 truncated peptide to fold independently. This distinction led us to explore granulins from the zebrafish model organism. Here we show that the mini-granulin fold occurs in a naturally occurring paragranulin (half-domain) from zebrafish, and is also present in a truncated form of a full-length zebrafish granulin, suggesting this structure might be a common property in either naturally occurring or engineered N-terminally truncated granulins and the carp granulin-1 folding is an anomaly. The in vitro folding yield is significantly higher in the naturally occurring paragranulin, but only the truncated zebrafish granulin peptide promoted the proliferation of fibroblasts consistent with a growth factor function, and therefore the function of the paragranulin remains unknown. These findings provide insight into the folding and evolution of granulin domains and might be useful in the elucidation of the structural features important for bioactivity to aid the design of more potent and stable analogues for the development of novel wound healing agents.