Lung injury during LPS-induced inflammation occurs independently of the receptor P2Y1

Serum sSelectin-L is an early specific indicator of radiation injury

Objective

It's crucial to identify an easily detectable biomarker that is specific to radiation injury in order to effectively classify injured individuals in the early stage in large-scale nuclear accidents.

Methods

C57BL/6J mice were subjected to whole-body and partial-body γ irradiation, as well as whole-body X-ray irradiation to explore the response of serum sSelectin-L to radiation injury. Then, it was compared with its response to lipopolysaccharide-induced acute infection and doxorubicin-induced DNA damage to study the specificity of sSelectin-L response to radiation. Furthermore, it was further evaluated in serum samples from nasopharyngeal carcinoma patients before and after radiotherapy. Simulated rescue experiments using Amifostine or bone marrow transplantation were conducted in mice with acute radiation syndrome to determine the potential for establishing sSelectin-L as a prognostic marker. The levels of sSelectin-L were dynamically measured using the ELISA method.

Results

Selectin-L is mainly expressed in hematopoietic tissues and lymphatic tissues. Mouse sSelectin-L showed a dose-dependent decrease from 1 day after irradiation and exhibited a positive correlation with lymphocyte counts. Furthermore, the level of sSelectin-L reflected the degree of radiation injury in partial-body irradiation mice and in nasopharyngeal carcinoma patients. sSelectin-L was closely related to the total dose of γ or X ray. There was no significant change in the sSelectin-L levels in mice intraperitoneal injected with lipopolysaccharide or doxorubicin. The sSelectin-L was decreased slower and recovered faster than lymphocyte count in acute radiation syndrome mice treated with Amifostine or bone marrow transplantation.

Conclusions

Our study shows that sSelectin-L has the potential to be an early biomarker to classify injured individuals after radiation accidents, and to be a prognostic indicator of successful rescue of radiation victims.

Lentinan and β-glucan extract from shiitake mushroom, Lentinula edodes, alleviate acute LPS-induced hematological changes in mice

Objectives

Immunomodulatory activity of β-glucans of shiitake mushroom (Lentinula edodes) has been known. We investigated whether β-glucans from L. edodes would attenuate the acute effects of lipopolysaccharides (LPS) on peripheral hematological parameters in mice.

Materials and Methods

An in-house β-glucans extract (BG) prepared from fruiting bodies of shiitake mushroom L. edodes was chemically measured and characterized using spectrophotometry and HPLC. Male BALB/c mice directly inhaled aerosolized LPS of 3 mg/ml and were treated with BG or commercial β-glucan (known as lentinan; LNT) (10 mg/kg bw) at 1 hr before or 6 hr after LPS inhalation. The blood samples were collected by cardiac puncture from euthanized mice at 16 hr post-treatment.

Results

The results showed a significant reduction in levels of blood parameters, including red blood cells (RBC), hemoglobin (HGB), hematocrit (HCT), and platelets (PLT); and a significant increase in blood lymphocyte counts in LPS-treated mice as compared with the control mice (P≤0.05). Total white blood cells, neutrophils, and monocyte counts did not show any significant difference among the groups. Treatment of LPS-challenged mice with LNT or BG significantly increased the levels of RBC, HGB, HCT, and PLT; and reduced blood lymphocyte counts as compared with LPS-treated mice (P≤0.05).

Conclusion

These findings suggest that β-glucans from L. edodes might be effective in attenuating the effects of inhaled LPS on peripheral blood parameters. Thus, these findings might be useful in acute inflammatory diseases particularly pulmonary infectious diseases in which the hematological parameters would be affected.

P2 Purinergic Signaling in the Distal Lung in Health and Disease

The distal lung provides an intricate structure for gas exchange in mammalian lungs. Efficient gas exchange depends on the functional integrity of lung alveoli. The cells in the alveolar tissue serve various functions to maintain alveolar structure, integrity and homeostasis. Alveolar epithelial cells secrete pulmonary surfactant, regulate the alveolar surface liquid (ASL) volume and, together with resident and infiltrating immune cells, provide a powerful host-defense system against a multitude of particles, microbes and toxicants. It is well established that all of these cells express purinergic P2 receptors and that purinergic signaling plays important roles in maintaining alveolar homeostasis. Therefore, it is not surprising that purinergic signaling also contributes to development and progression of severe pathological conditions like pulmonary inflammation, acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and pulmonary fibrosis. Within this review we focus on the role of P2 purinergic signaling in the distal lung in health and disease. We recapitulate the expression of P2 receptors within the cells in the alveoli, the possible sources of ATP (adenosine triphosphate) within alveoli and the contribution of purinergic signaling to regulation of surfactant secretion, ASL volume and composition, as well as immune homeostasis. Finally, we summarize current knowledge of the role for P2 signaling in infectious pneumonia, ALI/ARDS and idiopathic pulmonary fibrosis (IPF).

Antidepressive properties of microglial stimulation in a mouse model of depression induced by chronic unpredictable stress

The decrease of microglia in the hippocampus is a novel mechanism for depression onset. Reversal of this decrease can ameliorate stress-induced depression-like behaviors in rodents. However, the property of this therapeutic strategy remains unclear. We addressed this issue by designing a series of behavioral experiments. Results showed that a single lipopolysaccharide (LPS) injection at the dose of 75 and 100 μg/kg, but not at 30 or 50 μg/kg, produced obvious antidepressant effects in chronic unpredictable stress (CUS) mice at 5 h after the drug administration. In the time-dependent experiment, a single LPS injection (100 μg/kg) ameliorated the CUS-induced depression-like behaviors in mice at 5 and 8 h, but not at 3 h, after the drug administration. The antidepressant effect of a single LPS injection persisted at least 10 days and disappeared at 14 days after the drug administration. 14 days after the first injection, a second LPS injection (100 μg/kg) still produced antidepressant effects in chronically-stressed mice who re-displayed depression-like behaviors at 5 h after the drug administration. The antidepressant effect of LPS appears to be dependent on microglia, as at 5 h after LPS administration (100 μg/kg), the CUS-induced decrease in microglial numbers and Iba-1 mRNA levels in the hippocampus was reversed markedly, and inhibition of microglia by minocycline (40 mg/kg) or PLX33297 (290 mg/kg) prevented the antidepressant effect of LPS in CUS mice. These results indicate that a single LPS injection displays rapid and sustained antidepressant effects in chronically stressed mice likely through stimulating hippocampal microglia.

Psoriasis-Like Inflammation Induced Renal Dysfunction through the TLR/NF-κB Signal Pathway

Pathological studies have shown an association between psoriasis and renal injury (RI), but the mechanism between RI and psoriasis was still unclear. This paper was designed to investigate the relationship and mechanism between psoriasis-like inflammation and renal injury in BALB/C mice. Mice were topically smeared imiquimod followed by various analyses in skin lesions, urine protein, kidney/serum inflammatory cytokines, kidney function, podocyte membrane proteins, and toll-like receptors/nuclear factor kappa-b (TLR/NF-κB) pathway-associated proteins. Meanwhile, lipopolysaccharide (LPS) and dexamethasone (DEX) were intraperitoneally injected to promote and inhibit inflammation accompanied by imiquimod to elaborate the relevance between inflammatory levels and RI. In the model group, the Psoriasis Area and Severity Index (PASI) scores of scaly and erythema obviously increased (p < 0.01), creatinine and blood urea nitrogen significantly increased (p < 0.01), the positive area of hematoxylin-eosin (HE) and periodic acid-Schiff (PAS) staining in kidney increased (p < 0.01), malondialdehyde significantly increased with superoxide dismutase (SOD) decreased (p < 0.01), 24-hour urine protein increased and the expressions of podocin and CD2 associate protein (CD2AP) decreased (p < 0.01), and kidney/serum inflammatory factors (IL-17, IL-1β, IL-6, TNF-α, and IL-22) and TLR/NF-κB-related expression (TLR2, TLR4, MyD88, and NF-κBp65) all increased (p < 0.01). The RI was aggravated with the TLR/NF-κB related expression being upregulated by LPS (p < 0.05). On the contrary, the RI was alleviated by DEX (p < 0.05). Our data showed that psoriasis-like inflammation damaged the renal function via the TLR/NF-κB signal pathway. Inhibiting TLR/NF-κB-related protein expression may be effective for the treatment of RI caused by psoriasis.

Crosstalk between Platelet and Bacteria: A Therapeutic Prospect

Platelets are typically recognized for their roles in the maintenance of hemostasis and vascular wall repair to reduce blood loss. Beyond hemostasis, platelets also play a critical role in pathophysiological conditions like atherosclerosis, stroke, thrombosis, and infections. During infection, platelets interact directly and indirectly with bacteria through a wide range of cellular and molecular mechanisms. Platelet surface receptors such as GPIbα, FcγRIIA, GPIIbIIIa, and TLRs, etc. facilitate direct interaction with bacterial cells. Besides, the indirect interaction between platelet and bacteria involves host plasma proteins such as von Willebrand Factor (vWF), fibronectin, IgG, and fibrinogen. Bacterial cells induce platelet activation, aggregation, and thrombus formation in the microvasculature. The activated platelets induce the Neutrophil Extracellular Traps (NETs) formation, which further contribute to thrombosis. Thus, platelets are extensively anticipated as vital immune modulator cells during infection, which may further lead to cardiovascular complications. In this review, we cover the interaction mechanisms between platelets and bacteria that may lead to the development of thrombotic disorders. Platelet receptors and other host molecules involved in such interactions can be used to develop new therapeutic strategies to combat against infection-induced cardiovascular complications. In addition, we highlight other receptor and enzyme targets that may further reduce infection-induced platelet activation and various pathological conditions.

Clopidogrel reduces lipopolysaccharide-induced inflammation and neutrophil-platelet aggregates in an experimental endotoxemic model

Platelet activation contributes to organs failure in inflammation and plays an important role in endotoxemia. Clopidogrel inhibits platelet aggregation and activation. However, the role of clopidogrel in modulating inflammatory progression of endotoxemia remains largely unexplored. Therefore, we investigated the role of clopidogrel on the activation of platelet and leukocytes in lipopolysaccharide (LPS)-induced inflammation in mice. Animals were treated with clopidogrel or vehicle before LPS induction. The expression of neutrophil-platelet aggregates and platelet activation and tissue factor was determined. Immunofluorescence was used to analyze platelet-leukocyte interactions and tissue factor (TF) expression on leukocytes. Clopidogrel pretreatment markedly decreased lung damage, inhibited platelet-neutrophil aggregates and TF expression. In addition, clopidogrel reduced thrombocytopenia and affected the number of circulating white blood cell in endotoxemia mice. Moreover, clopidogrel also reduced platelet shedding of CD40L and CD62P in endotoxemic mice. Taken together, clopidogrel played an important role through reducing platelet activation and inflammatory process in endotoxemia.

Functional characterization of purinergic P2Y2 and P2Y12 receptors involved in Japanese flounder (Paralichthys olivaceus) innate immune responses

G-protein-coupled P2Y receptors activated by extracellular nucleotides play important roles under different physiological and pathophysiological conditions in mammals. To investigate the immunological relevance of P2Y receptors in fish, we identified and characterized the P2Y₂ and P2Y₁₂ receptors in Japanese flounder Paralichthys olivaceus. The P. olivaceus P2Y₂ and P2Y₁₂ receptors harbor seven transmembrane domains but share only 24% sequence identity. Real-time PCR analysis revealed the constitutive but unequal mRNA expression pattern of P2Y₂R and P2Y₁₂R in normal Japanese flounder tissues with the dominant expression of P2Y₂R in head kidney and blood and P2Y₁₂R in hepatopancreas. In addition, the expression of P2Y₂ and P2Y₁₂ receptors was markedly modulated by PAMPs stimulation and Edwardsiella tarda infection. Furthermore, blockage of P2Y₁₂R potently increased ADP-activated pro-inflammatory cytokine IL-1beta gene expression in the head kidney macrophages (HKMs). Moreover, inhibition of P2Y₂ and P2Y₁₂ receptor activity with their respective potent antagonists significantly altered some of the LPS-induced pro-inflammatory cytokine gene expression in the HKMs. However, blockade of P2Y₁₂R did not affect the poly(I:C)-induced pro-inflammatory cytokine gene expression examined in the HKMs. Collectively, we have for the first time reported the role of purinergic P2Y₂ and P2Y₁₂ receptors in fish innate immunity. Our findings have also addressed the importance of extracellular ATP and its metabolites in fish innate immune responses.

Purinergic Signalling: Therapeutic Developments

Purinergic signalling, i.e., the role of nucleotides as extracellular signalling molecules, was proposed in 1972. However, this concept was not well accepted until the early 1990's when receptor subtypes for purines and pyrimidines were cloned and characterised, which includes four subtypes of the P1 (adenosine) receptor, seven subtypes of P2X ion channel receptors and 8 subtypes of the P2Y G protein-coupled receptor. Early studies were largely concerned with the physiology, pharmacology and biochemistry of purinergic signalling. More recently, the focus has been on the pathophysiology and therapeutic potential. There was early recognition of the use of P1 receptor agonists for the treatment of supraventricular tachycardia and A2A receptor antagonists are promising for the treatment of Parkinson's disease. Clopidogrel, a P2Y12 antagonist, is widely used for the treatment of thrombosis and stroke, blocking P2Y12 receptor-mediated platelet aggregation. Diquafosol, a long acting P2Y2 receptor agonist, is being used for the treatment of dry eye. P2X3 receptor antagonists have been developed that are orally bioavailable and stable in vivo and are currently in clinical trials for the treatment of chronic cough, bladder incontinence, visceral pain and hypertension. Antagonists to P2X7 receptors are being investigated for the treatment of inflammatory disorders, including neurodegenerative diseases. Other investigations are in progress for the use of purinergic agents for the treatment of osteoporosis, myocardial infarction, irritable bowel syndrome, epilepsy, atherosclerosis, depression, autism, diabetes, and cancer.