GSK3β negatively regulates LPS-induced osteopontin expression via inhibiting its transcription

Lithium chloride stimulates bone formation in extraction socket repair in rats

PURPOSE

Previous evidence shows that lithium chloride (LiCl), a suppressor of glycogen synthase kinase-3β (GSK-3β), may enhance bone formation in several medical and dental conditions. Thus, the purpose of the current study was to assess the effects of LiCl on extraction socket repair in rats.

METHODS

Thirty rats were randomly assigned into a control group (administration of water; n = 15) or a LiCl group (administration of 150 mg/kg of LiCl; n = 15). LiCl and water were given every other day, starting at 7 days before the extraction of upper first molars until the end of each experiment period. Histological sections from five rats per group were obtained at 10, 20, and 30 days post-extractions. Histometrical analysis of newly formed bone (NB) and the levels of tartrate-resistant acid phosphatase (TRAP)-stained cells were evaluated at 10, 20, and 30 days post-extractions. Immunohistochemical staining for receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin (OPG), bone sialoprotein (BSP), osteocalcin (OCN), and osteopontin (OPN) was assessed at 10 days post-extractions.

RESULTS

The LiCl group had a greater proportion of NB than the control group at 20 days (P < 0.05). At 30 days, the rate of TRAP-stained cells was lower in the LiCl group than in the control group (P < 0.05). At 10 days, the LiCl group presented stronger staining for OPG, BSP, OPN, and OCN, when compared to the control group (P < 0.05).

CONCLUSION

Systemic LiCl enhanced extraction socket repair, stimulated an overall increase in bone formation markers, and restricted the levels of TRAP in rats.

Blocking osteopontin expression attenuates neuroinflammation and mitigates LPS-induced depressive-like behavior in mice

INTRODUCTION

Neuroinflammation plays an important role in the development of major depressive disorder (MDD). Osteopontin (OPN) is one of the key molecules involved in neuroinflammation. We demonstrate here for the first time a key role of OPN in lipopolysaccharide (LPS)-induced depressive-like behavioral syndrome.

METHODS

Systemic administration of LPS (5 mg/kg) mimics distinct depressive-like behavior, which could significantly upregulate OPN expression in microglia/macrophage in the hippocampus. The neurobehavioral assessments, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), Western blot, immunofluorescent staining, flow cytometry cell staining and Golgi staining were performed.

RESULTS

Similar to fluoxetine treatment (the positive control), OPN knockdown with shRNA lentivirus markedly reversed LPS-induced depressive-like behavior. Moreover, knockdown of OPN suppressed LPS-induced proinflammatory cytokine expression, microglial activation, dendritic spines loss, as well as unregulated PSD-95 and BDNF in the hippocampus.

CONCLUSION

We demonstrated that targeting OPN expression in microglia/macrophage might help to rescue LPS-induced depressive-like behavior. The underlying mechanism may relate to the modulation of neuroinflammation, BDNF signaling and synaptic structural complexity.

Systemic Lithium Chloride Administration Improves Tooth Extraction Wound Healing in Estrogen-Deficient Rats

The purpose of this investigation was to evaluate the effects of lithium chloride (LiCl) on the socket healing of estrogen-deficient rats. Seventy-two rats were allocated into one of the following groups: Control, Ovariectomy and LiCl (150 mg/kg/2 every other day orally) + Ovariectomy. Animals received LiCl or water from the 14th day post-ovariectomy, until the completion of the experiment. On the 21st day after ovariectomy, the first molars were extracted. Rats were euthanized on the 10th, 20th and 30th days following extractions. Bone healing (BH), TRAP positive cells and immunohistochemical staining for OPG, RANKL, BSP, OPN and OCN were evaluated. The Ovariectomy group presented decreased BH compared to the LiCl group at 10 days, and the lowest BH at 20 days (p<0.05). At 30 days, the Ovariectomy and LiCl-groups presented lower BH than that of the Control (p<0.05). The number of TRAP-stained cells was the lowest in the LiCl group at 20 days and the highest in the Ovariectomy group at 30 days (p<0.05). At 10 days of healing, the LiCl group demonstrated stronger staining for all bone markers when compared to the other groups, while the Ovariectomy group presented higher RANKL expression than that of the Control (p<0.05). LiCl enhanced bone healing in rats with estrogen deficiency, particularly in the initial healing phases. However, as data on the effects of lithium chloride on bone tissue are still preliminary, more studies related to its toxicity and protocol of administration are necessary before its application in clinical practice.

A complex interplay between the extracellular matrix and the innate immune response to microbial pathogens

The role of the host extracellular matrix (ECM) in infection tends to be neglected. However, the complex interactions between invading pathogens, host tissues and immune cells occur in the context of the ECM. On the pathogen side, a variety of surface and secreted molecules, including microbial surface components recognizing adhesive matrix molecules and tissue-degrading enzymes, are employed that interact with different ECM proteins to effectively establish an infection at specific sites. Microbial pathogens can also hijack or misuse host proteolytic systems to modify the ECM, evade immune responses or process biologically active molecules such as cell surface receptors and cytokines that direct cell behaviour and immune defence. On the host side, the ECM composition and three-dimensional ultrastructure undergo significant modifications, which have a profound impact on the specific signals that the ECM conveys to immune cells at the forefront of infection. Unexpectedly, activated immune cells participate in the remodelling of the local ECM by synthesizing ECM glycoproteins, proteoglycans and collagen molecules. The close interplay between the ECM and the innate immune response to microbial pathogens ultimately affects the outcome of infection. This review explores and discusses recent data that implicate an active role for the ECM in the immune response to infection, encompassing antimicrobial activities, microbial recognition, macrophage activation, phagocytosis, leucocyte population balance, and transcriptional and post-transcriptional regulation of inflammatory networks, and may foster novel antimicrobial approaches.

Absence of IL-10 production by human PBMCs co-cultivated with human cells expressing or secreting retroviral immunosuppressive domains

Immunosuppression by retroviruses including the human immunodeficiency virus—1 (HIV-1) is well known, however the mechanisms how retroviruses induce this immunosuppression is not fully investigated. It was shown that non-infectious retroviral particles as well as retroviral or recombinant retroviral transmembrane envelope (TM) proteins demonstrated immunosuppressive properties. The same was shown for peptides corresponding to a highly conserved domain in the TM protein. This domain is called immunosuppressive (ISU) domain and it induces modulation of the cytokine release of peripheral blood mononuclear cells (PBMCs) from healthy donors. In addition, it changes the gene expression of these cells. Common indications for the immunosuppressive activity were tumour growth in vivo and interleukin—10 (IL-10) release from human PBMCs in vitro. Single mutations in the ISU domain abrogated the immunosuppressive activity. In order to develop a new model system for the expression of the ISU domain and presentation to PBMCs which is not prone to possible endotoxin contaminations, two expression systems were developed. In the first system, designated pOUT, retroviral proteins containing the ISU domain were expressed and released into the cell culture medium, and in the second system, tANCHOR, the ISU domain was presented by a tetraspanin-anchored sequence on the cell surface of human cells. Both systems were exploited to express the wild-type (wt) ISU domains of HIV-1, of the porcine endogenous retrovirus (PERV) and of the murine leukaemia virus (MuLV) as well as to express mutants (mut) of these ISU domains. PERV is of special interest in the context of virus safety of xenotransplantation using pig organs. Expression of the TM proteins was demonstrated by confocal laser scanning microscopy, ELISA and Western blot analyses using specific antibodies. However, when cells expressing and releasing the ISU were co-incubated with human PBMCs, no increased production of IL-10 was observed when compared with the mutants. Similar results were obtained when the released TM proteins were concentrated by immunoprecipitation and added to PBMCs. We suggest that the absence of IL-10 induction can be explained by a low amount of protein, by the lack of a biologically active conformation or the absence of additional factors.

GSK-3β inhibitor attenuates urinary albumin excretion in type 2 diabetic db/db mice, and delays epithelial-to-mesenchymal transition in mouse kidneys and podocytes

The mechanism underlying epithelial‑to‑mesenchymal transition (EMT) caused by high glucose (HG) stimulation in diabetic nephropathy (DN) remains to be fully elucidated. The present study investigated the effects of HG on EMT and the activity of glycogen synthase kinase 3β (GSK‑3β) in podocytes and the kidneys of db/db mice, and assessed the effects of (2'Z, 3'E)‑6‑bromoindirubin‑3'‑oxime (BIO), an inhibitor of GSK‑3β, on EMT and glomerular injury. The resulting data showed that the activity of GSK‑3β was upregulated by HG and downregulated by BIO in the podocytes and the renal cortex. The expression levels of epithelial markers, including nephrin, podocin and synaptopodin, were decreased by HG and increased by BIO, whereas the reverse were true for mesenchymal markers, including α‑smooth muscle actin (α‑SMA) and fibronectin. The expression levels of β‑catenin and Snail, in contrast to current understanding of the Wnt signaling pathway, were increased by HG and decreased by BIO. In addition, expression of the vitamin D receptor (VDR) was decreased by HG and increased by BIO. In conclusion, the present study revealed that the mechanism by which BIO inhibited HG‑mediated EMT in podocytes and the renal cortex was primarily due to the VDR. Treatment with BIO protected renal function by maintaining the integrity of the filtration membrane and decreasing UAE, but not by regulating blood glucose. Therefore, GSK‑3β may be used as a sensitive biomarker of DN, and its inhibition by BIO may be effective in the treatment of DN.