Binding Immunoglobulin Protein (BIP) Inhibits TNF-α-Induced Osteoclast Differentiation and Systemic Bone Loss in an Erosive Arthritis Model

Gut-X Axis and Its Role in Poultry Bone Health: A Review

The normal development and growth of bones are critical for poultry health. With the rapid increase in poultry growth rates achieved over the last few decades, juvenile meat-type poultry exhibit a high incidence of leg weakness and lameness. These issues are significant contributors to poor animal welfare and substantial economic losses. Understanding the potential etiology of bone problems in poultry will aid in developing treatments for bone diseases. The gut microbiota represents the largest micro-ecosystem in animals and is closely related to many metabolic disorders, including bone disease. It achieves this by secreting secondary metabolites and coordinating with various tissues and organs through the circulatory system, which leads to the concept of the gut-X axis. Given its importance, modulating gut microbiota to influence the gut-X axis presents new opportunities for understanding and developing innovative therapeutic approaches for poultry bone diseases. In light of the extensive literature on this topic, this review focuses on the effects of gut microbiota on bone density and strength in poultry, both directly and indirectly, through the regulation of the gut-X axis. Our aim is to provide scientific insights into the bone health problems faced by poultry.

Development of an efficient expression system for human chaperone BiP in Pichia pastoris: production optimization and functional validation

BACKGROUND

Human BiP, or GRP78, is a molecular chaperone mainly found in the endoplasmic reticulum (ER). However, a growing amount of data also associates BiP with many distinct functions in subcellular locations outside the ER. Notably, several diseases have been BiP-related, so the protein could potentially be used for therapeutic purposes. This study aimed to optimize a high cell-density fermentation process for the production of recombinant human BiP (rhBiP) in yeast Pichia pastoris in a mineral medium.

RESULTS

P. pastoris cells successfully synthesized and secreted full-length rhBiP protein in a complex growth medium. However, secreted rhBiP titer was considerably lower when P. pastoris was cultivated in a defined mineral basal salt medium (BSM). During rhBiP synthesis optimization in shake flasks, it was found that the addition of reducing compounds (DTT or TCEP) to mineral BSM medium is essential for high-yield rhBiP production. Furthermore, rhBiP secretion in the BSM medium was significantly increased by feeding yeast with an additional carbon source. The addition of 2 mM DTT and 0.5-1.0% of glucose/glycerol to the BSM medium increased rhBiP titer ~ 8 times in the shake flasks. Glucose/methanol mixture feeding with added 2 mM DTT before induction was applied in high-density P. pastoris fermentation in bioreactor. Oxygen-limited fermentation strategy allowed to achieve ~ 70 mg/L rhBiP in BSM medium. Hydrophobic interaction and anion exchange chromatography were used for rhBiP protein purification. Approximately 45 mg rhBiP was purified from 1 L growth medium, and according to SDS-PAGE, ~ 90% purity was reached. According to data presented in this study, rhBiP protein derived from P. pastoris is a full-length polypeptide that has ATPase activity. In addition, we show that P. pastoris-derived rhBiP effectively inhibits neurodegenerative disease-related amyloid beta 1-42 (Aβ42) peptide and alpha-synuclein (α-Syn) protein aggregation in vitro.

CONCLUSIONS

A scalable bioprocess to produce rhBiP in P. pastoris was developed, providing a high yield of biologically active protein in a chemically defined mineral medium. It opens a source of rhBiP to accelerate further therapeutic applications of this important protein.

The Differential Expressions and Associations of Intracellular and Extracellular GRP78/Bip with Disease Activity and Progression in Rheumatoid Arthritis

GRP78/BiP, a stress-induced protein and autoantigen in rheumatoid arthritis (RA), exhibits different expressions in various biological fluids and tissues, including blood, synovial fluid (SF), and synovium, all of which are pertinent to the disease activity and progression of RA; however, there is a scarcity of data linking both intracellular and extracellular GRP78/Bip to disease activity and progression of RA. This study was undertaken to investigate the differential expression of GRP78/Bip in blood, SF, and synovium, and to determine their association with disease activity and progression of RA. Patients with RA, osteoarthritis (OA), and traumatic meniscal injury (TMI) without radiographic OA were consecutively recruited for the study. Among patients with RA, six different subgroups were established based on their disease activity and progression. Disease activity was measured using the DAS28 (Disease activity scores in 28 joints) criterion, while disease progression was evaluated using the Steinbrocker classification grade. The levels of GRP78/Bip, TNF-α, and IL-10 were significantly elevated in the serum, SF, and synovium of patients with RA when compared to both the control (CON, TMI Patients) and the inflammation control (iCON, OA Patients) groups (p < 0.05). In terms of disease activity status, as opposed to remission status in RA, the levels of GRP78/Bip, TNF-α, and IL-10 were all elevated in serum and synovium (p < 0.05). However, GRP78/Bip and IL-10 levels were found to be reduced in SF, while TNF-α levels remained elevated. With respect to disease progression in RA, GRP78/Bip levels exhibited a positive correlation with both the stage of RA and the levels of TNF-α and IL-10 in serum and synovium. Nonetheless, a negative correlation was observed between GRP78/Bip levels and the stage of RA in SF, while positive correlations with the levels of TNF-α and IL-10 persisted. The differential expression of GRP78/Bip in blood, SF, and synovium indicated that the potential role and function of GRP78/Bip might vary depending on its specific location within these biological fluids and tissues. The presence of intracellular and extracellular GRP78/Bip was associated with disease activity and progression of RA, suggesting the involvement of GRP78/Bip in the pathogenesis and development of this debilitating autoimmune disorder, as well as its potential as a biomarker for monitoring disease activity and progression of RA.

The Biologic IRL201805 Alters Immune Tolerance Leading to Prolonged Pharmacodynamics and Efficacy in Rheumatoid Arthritis Patients

A homologue of binding immunoglobulin protein/BiP-IRL201805 alters the function of immune cells in pre-clinical in vivo and in vitro studies. The aim of the study was to select biomarkers that clearly delineate between RA patients who respond to IRL201805 and placebo patients and reveal the immunological mode of action of IRL201805 driving the extended pharmacodynamics observed in responding patients. Biomarkers that distinguished between responding patients and placebo patients included downregulation of serum interferon-γ and IL-1β; upregulation of anti-inflammatory mediators, serum soluble CTLA-4, and intracellular monocyte expression of IDO; and sustained increased CD39 expression on CD3+CD4+CD25hi CD127lo regulatory T cells. In the responding patients, selected biomarkers verified that the therapeutic effect could be continuous for at least 12 weeks post-infusion. In secondary co-culture, pre-infusion PBMCs cultured 1:1 with autologous PBMCs, isolated at later time-points during the trial, showed significantly inhibited IL-6 and IL-1β production upon anti-CD3/CD28 stimulation demonstrating IRL201805 alters the function of immune cells leading to prolonged pharmacodynamics confirmed by biomarker differences. IRL201805 may be the first of a new class of biologic drug providing long-term drug-free therapy in RA.

The therapeutic mavericks: Potent immunomodulating chaperones capable of treating human diseases

Two major chaperones, calreticulin (CRT) and binding immunoglobulin protein (GRP78/BiP) dependent on their location, have immunoregulatory or anti-inflammatory functions respectively. CRT induces pro-inflammatory cytokines, dendritic cell (DC) maturation and activates cytotoxic T cells against tumours. By contrast, GRP78/BiP induces anti-inflammatory cytokines, inhibits DC maturation and heightens T-regulatory cell responses. These latter functions rebalance immune homeostasis in inflammatory diseases, such as rheumatoid arthritis. Both chaperones are therapeutically relevant agents acting primarily on monocytes/DCs. Endogenous exposure of CRT on cancer cell surfaces acts as an 'eat-me' signal and facilitates improved elimination of stressed and dying tumour cells by DCs. Therefore, therapeutics that promote endogenous CRT translocation to the cell surface can improve the removal of cancer cells. However, infused recombinant CRT dampens this cancer cell eradication by binding directly to the DCs. Low levels of endogenous BiP appear as a surface biomarker of endoplasmic reticulum (ER) stress in some types of tumour cells, a reflection of cells undergoing proliferation, in which resulting hypoxia and nutrient deprivation perturb ER homeostasis triggering the unfolded protein response, leading to increased expression of GRP78/BiP and altered cellular location. Conversely, infusion of an analogue of GRP78/BiP (IRL201805) can lead to long-term immune resetting and restoration of immune homeostasis. The therapeutic potential of both chaperones relies on them being relocated from their intracellular ER environment. Ongoing clinical trials are employing therapeutic interventions to either enhance endogenous cell surface CRT or infuse IRL201805, thereby triggering several disease-relevant immune responses leading to a beneficial clinical outcome.

ER-stress-induced secretion of circulating glucose-regulated protein 78kDa (GRP78) ameliorates pulmonary artery smooth muscle cell remodelling

Pulmonary arterial hypertension (PAH) is driven by vascular remodelling due to inflammation and cellular stress, including endoplasmic reticulum stress (ER stress). The main ER-stress chaperone, glucose-regulated protein 78 kDa (GRP78), is known to have protective effects in inflammatory diseases through extracellular signalling. The aim of this study is to investigate its significance in PAH. Human pulmonary arterial smooth muscle cells (PASMC) were stimulated with compounds that induce ER stress, after which the secretion of GRP78 into the cell medium was analysed by western blot. We found that when ER stress was induced in PASMC, there was also a time-dependent secretion of GRP78. Next, naïve PASMC were treated with conditioned medium (CM) from the ER-stressed donor PASMC. Incubation with CM from ER-stressed PASMC reduced the viability, oxidative stress, and expression of inflammatory and ER-stress markers in target cells. These effects were abrogated when the donor cells were co-treated with Brefeldin A to inhibit active secretion of GRP78. Direct treatment of PASMC with recombinant GRP78 modulated the expression of key inflammatory markers. Additionally, we measured GRP78 plasma levels in 19 PAH patients (Nice Group I) and correlated the levels to risk stratification according to ESC guidelines. Here, elevated plasma levels of GRP78 were associated with a favourable risk stratification. In conclusion, GRP78 is secreted by PASMC under ER stress and exhibits protective effects from the hallmarks of PAH in vitro. Circulating GRP78 may serve as biomarker for risk adjudication of patients with PAH. Proposed mechanism of ER-stress-induced GRP78 secretion by PASMC. Extracellular GRP78 can be measured as a circulating biomarker and is correlated with favourable clinical characteristics. Conditioned medium from ER-stressed PASMC reduces extensive viability, ROS formation, inflammation, and ER stress in target cells. These effects can be abolished by blocking protein secretion in donor cells by using Brefeldin A.

Hsp90 inhibition protects brain endothelial cells against LPS-induced injury

Dysfunction of the blood-brain barrier (BBB) endothelium increases infiltration of lymphocytes and innate immune cells in the brain, leading to the development of neurological disorders. Heat shock protein 90 (Hsp90) inhibitors are anti-inflammatory agents and P53 inducers, which reduce the production of reactive oxygen species (ROS) in a diverse variety of human tissues. In this study, we investigate the effects of those compounds in LPS-induced brain endothelial inflammation, by utilizing human cerebral microvascular endothelial cells (hCMEC/D3). Our results suggest that Hsp90 inhibitors suppress inflammation by inhibiting the LPS-induced signal transducer and activator of transcription 3 (STAT3); and P38 activation. Moreover, those compounds reduce the P53 suppressors murine double minute 2 (MDM2) and murine double minute 4 (MDM4). Immunoglobulin heavy chain binding protein/glucose-regulated protein 78 (BiP/Grp78)-a key element of endothelial barrier integrity-was also increased by Hsp90 inhibition. Hence, we conclude that application of Hsp90 inhibitors in diseases related to BBB dysfunction may deliver a novel therapeutic possibility in the affected population.

The M-CSF receptor in osteoclasts and beyond

Colony-stimulating factor 1 receptor (CSF1R, also known as c-FMS) is a receptor tyrosine kinase. Macrophage colony-stimulating factor (M-CSF) and IL-34 are ligands of CSF1R. CSF1R-mediated signaling is crucial for the survival, function, proliferation, and differentiation of myeloid lineage cells, including osteoclasts, monocytes/macrophages, microglia, Langerhans cells in the skin, and Paneth cells in the intestine. CSF1R also plays an important role in oocytes and trophoblastic cells in the female reproductive tract and in the maintenance and maturation of neural progenitor cells. Given that CSF1R is expressed in a wide range of myeloid cells, altered CSF1R signaling is implicated in inflammatory, neoplastic, and neurodegenerative diseases. Inhibiting CSF1R signaling through an inhibitory anti-CSF1R antibody or small molecule inhibitors that target the kinase activity of CSF1R has thus been a promising therapeutic strategy for those diseases. In this review, we cover the recent progress in our understanding of the various roles of CSF1R in osteoclasts and other myeloid cells, highlighting the therapeutic applications of CSF1R inhibitors in disease conditions.

Drugs directed at a key signaling receptor involved in breaking down bone tissue could help treat diseases marked by pathological bone loss and destruction. In a review article, Kyung-Hyun Park-Min and colleagues from the Hospital for Special Surgery in New York, USA, discuss the essential roles played by the colony-stimulating factor 1 receptor (CSF1R) protein in the survival, function, proliferation and differentiation of myeloid lineage stem cells in the bone marrow, including bone-resorbing osteoclasts. They explore the links between the CSF1R-mediated signaling pathway and diseases such as cancer and neurodegeneration. The authors largely focus on bone conditions, highlighting mouse studies in which CSF1R-blocking drugs were shown to ameliorate bone loss and inflammatory symptoms in models of arthritis, osteoporosis and metastatic cancer. Clinical trials are ongoing to test therapeutic applications.

Muscone Ameliorates Ovariectomy-Induced Bone Loss and Receptor Activator of Nuclear Factor-κb Ligand-Induced Osteoclastogenesis by Suppressing TNF Receptor-Associated Factor 6-Mediated Signaling Pathways

Postmenopausal osteoporosis is caused by the deficiency of estrogen, which breaks bone homeostasis and induces levels of pro-inflammatory cytokines. Muscone is a potent anti-inflammatory agent and is used to treat bone fracture in traditional Chinese medicine. However, its anti-osteoclastogenic effects remain unclear. For in vitro study, morphology tests of osteoclastogenesis were firstly performed. And then, factors in RANK-induced NF-κB and MAPK pathways were examined by RT-PCR and Western blot, and the binding of TNF receptor–associated factor (TRAF)6 to RANK was inspected by coimmunoprecipitation and immunofluorescence staining. For in vivo experiments, C57BL/6 ovariectomized (OVX) mice were used for detection, including H&E staining, TRAP staining, and micro CT. As a result, muscone reduced OVX-induced bone loss in mice and osteoclast differentiation in vitro, by inhibiting TRAF6 binding to RANK, and then suppressed NF-κB and MAPK signaling pathways. The expression of the downstream biomarkers was finally inhibited, including NFATc1, CTR, TRAP, cathepsin K, and MMP-9. The inflammatory factors, TNF-a and IL-6, were also reduced by muscone. Taken together, muscone inhibited the binding of TRAF6 to RANK induced by RANKL, thus blocking NF-kB and MAPK pathways, and down-regulating related gene expression. Finally, muscone inhibited osteoclastogenesis and osteoclast function by blocking RANK-TRAF6 binding, as well as downstream signaling pathways in vitro. Muscone also reduced ovariectomy-induced bone loss in vivo.