Osteopontin is critical to determine symptom severity of influenza through the regulation of NK cell population

Resveratrol exerts antiviral activity against pseudorabies virus through regulation of the OPN-ERK/JNK-IL-1β signaling axis

Pseudorabies virus (PRV) can infect most mammals and has caused significant economic losses in global pig production. The emergence of new mutants significantly reduces the protective effect of vaccination, indicating an urgent need for the development of specific therapeutic agents against PRV infection. In this study, we analyzed the changes in the cellular proteome after PRV infection in resveratrol-treated PK-15 cells using TMT quantitative proteomics combined with LC-MS/MS. The results identified the differential proteins osteopontin (iOPN) and interleukin-1 receptor accessory protein (IL-1RAP), which have significant biological implications. The regulation of OPN-IL-1β signaling by PRV infection was further studied through the OPN-ERK/JNK-IL-1β signaling axis. The transcriptional levels of OPN, C-JUN, IL-1RAP, and IL-1β, along with the protein levels of ERK, JNK, C-Jun, and their phosphorylated forms at 8, 12, and 16 h post-infection, were determined. The results showed that PRV infection inhibited the activation of this signaling axis, which was upregulated by resveratrol treatment. Down-regulation of OPN by siRNA increased PRV proliferation and inhibited the activation of the signaling axis, which was antagonized by resveratrol treatment. In PRV-infected mice, resveratrol treatment produced the same changes observed in vitro. The present study demonstrated that resveratrol can promote innate immune responses by regulating the OPN-ERK/JNK-IL-1β signaling axis, thereby activating host antiviral defenses against PRV infection. SIGNIFICANCE: Resveratrol targets the OPN-ERK/JNK-IL-1β axis to enhance innate immunity, offering a novel antiviral strategy against PRV infection. This study identifies OPN as a key regulator of host defense, linking ERK/JNK signaling to IL-1β-mediated antiviral responses. In vivo validation demonstrates resveratrol's therapeutic potential, reducing PRV replication and mortality in mice via immune pathway activation.

Human osteopontin: Potential clinical applications in cancer (Review)

Human osteopontin (OPN) is a glycosylated phosphoprotein which is expressed in a variety of tissues in the body. In recent years, accumulating evidence has indicated that the aberrant expression of OPN is closely associated with tumourigensis, progression and most prominently with metastasis in several tumour types. In this review, we present the current knowledge on the expression profiles of OPN and its main splice variants in human cancers, as well as the potential implications in patient outcome. We also discuss its putative clinical application as a cancer biomarker and as a therapeutic target.

Intracellular osteopontin stabilizes TRAF3 to positively regulate innate antiviral response

Osteopontin (OPN) is a multifunctional protein involved in both innate immunity and adaptive immunity. However, the function of OPN, especially the intracellular form OPN (iOPN) on innate antiviral immune response remains elusive. Here, we demonstrated that iOPN is an essential positive regulator to protect the host from virus infection. OPN deficiency or knockdown significantly attenuated virus-induced IRF3 activation, IFN-β production and antiviral response. Consistently, OPN-deficient mice were more susceptible to VSV infection than WT mice. Mechanistically, iOPN was found to interact with tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) and inhibit Triad3A-mediated K48-linked polyubiquitination and degradation of TRAF3 through the C-terminal fragment of iOPN. Therefore, our findings delineated a new function for iOPN to act as a positive regulator in innate antiviral immunity through stabilization of TRAF3.

Utility of Plasma Osteopontin Levels in Management of Community-Acquired Pneumonia

Osteopontin (OPN) is an essential cytokine involved in immune cell recruitment and an important regulator of inflammation. The purpose of this study was to examine differences in OPN plasma levels between before and after antibiotic treatment in hospitalized adult patients with community-acquired pneumonia (CAP). OPN levels were measured in 93 patients with CAP and 54 healthy controls using a commercial enzyme-linked immunosorbent assay (ELISA). The CURB-65, Pneumonia Severity Index (PSI), and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were used to determine the CAP severity in patients upon initial hospitalization. A decline in the number of white blood cells (WBCs) and neutrophils, and decreases in the levels of OPN and C-reactive protein (CRP) were observed after antibiotic treatment. Only the plasma level of OPN, but not CRP, was correlated with the severity of CAP based on the PSI (r = 0.514, p < 0.001), CURB-65 (r = 0.396, p < 0.001), and APACHE II scores (r = 0.473, p < 0.001). The OPN level also showed a significant correlation with the length of hospital stay (r = 0.210, p = 0.044). In conclusion, plasma level of OPN may act as diagnostic adjuvant biomarkers for CAP and further play a role in clinical assessment of the severity of CAP, which could potentially guide the development of treatment strategies.

Osteopontin Exacerbates Pulmonary Damage in Influenza-Induced Lung Injury

The level of osteopontin (OPN) increases during bacterial lung infection. However, the OPN level in virus-induced lung injury is unclear, and the relationship between the hyer-production of OPN and lung injury remains to be thoroughly understood. Therefore, we sought to determine whether a relationship exists between OPN and pulmonary damage. Particularly, pulmonary edema and the destruction of pulmonary tissue. In this study, we found that the OPN level was significantly elevated in patients with pulmonary damage, and there was a positive correlation between the OPN serum level and disease severity in influenza lung injury. The epithelial sodium channel (ENaC) is the main mechanism of clearance of pulmonary edema fluid, and matrix metalloproteinase 7 (MMP7) can degrade the extracellular matrix. In lung epithelial cells, OPN markedly decreased the mRNA expression of the α-subunit of ENaC through integrin β3 and CD44 (OPN receptors); however, the expression of MMP7 was promoted by OPN interaction with integrin β1 and CD44. In addition, OPN increased the levels of tumor necrosis factor-α and interleukin-6. These findings suggested that OPN might increase influenza virus-induced lung injury by augmenting lung epithelial cell apoptosis and impairing ENaC and extracellular matrix destruction.

The osteopontin transgenic mouse is a new model for Sjögren's syndrome

Osteopontin (Opn) is a cytokine involved in both physiological and pathological processes, and is elevated in many autoimmune diseases. Sjögren's syndrome (SS) is an autoimmune disease with a strong female predilection characterized by lymphocytic infiltration of exocrine glands. We hypothesized that Opn contributes to SS pathogenesis. We examined an established SS model and found increased Opn locally and systemically. Next, we examined Opn transgenic (Opn Tg) mice for evidence of SS. Opn Tg animals exhibited lymphocytic infiltration of salivary and lacrimal glands, and Opn co-localized with the infiltrates. Moreover, saliva production was reduced, and SS autoantibodies were observed in the serum of these mice. Finally, female Opn Tg mice showed more severe disease compared to males. Taken together, these data support a role for Opn in SS pathogenesis. We identify a new model of spontaneous SS that recapitulates the human disease in terms of sex predilection, histopathology, salivary deficits, and autoantibodies.

Respiratory syncytial virus (RSV) infection in elderly mice results in altered antiviral gene expression and enhanced pathology

Elderly persons are more susceptible to RSV-induced pneumonia than young people, but the molecular mechanism underlying this susceptibility is not well understood. In this study, we used an aged mouse model of RSV-induced pneumonia to examine how aging alters the lung pathology, modulates antiviral gene expressions, and the production of inflammatory cytokines in response to RSV infection. Young (2-3 months) and aged (19-21 months) mice were intranasally infected with mucogenic or non-mucogenic RSV strains, lung histology was examined, and gene expression was analyzed. Upon infection with mucogenic strains of RSV, leukocyte infiltration in the airways was elevated and prolonged in aged mice compared to young mice. Minitab factorial analysis identified several antiviral genes that are influenced by age, infection, and a combination of both factors. The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes. Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age. In addition to delays in cytokine signaling and pattern recognition receptor induction, we found TLR7/8 signaling to be impaired in alveolar macrophages in aged mice. In vivo, induction of IL-1β and OPN were delayed but prolonged in aged mice upon RSV infection compared to young. In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

Role of NK cells in influenza infection

Within days after infection, natural killer (NK) cells are recruited to the lungs and play an essential role in the immune response against influenza infection. Through interactions with the virus itself, as well as viral-infected cells, NK cells secrete a variety of cytokines and can contain viral replication by killing infected cells early after influenza infection. However, the virus has means of evading NK cell responses, including escaping NK cell recognition through mutation of the viral hemagglutinin (HA) protein, regulating HA levels, and by directly infecting and destroying NK cells. Although much of our understanding of NK cell role in influenza infection has come from animal models, there is increasing information from human infection. Studies conducted during the 2009 H1N1 pandemic provided much needed information on the importance of NK cells during human infection and suggest that NK lymphopenia may correlate with increased disease severity. However, more information on how different influenza virus subtypes influence NK cell levels and activities, the role of the different NK cell receptors in infection, and the impact of NK cells on human infection, particularly in high risk populations is needed.