Inhibition of mesenchymal stromal cells' chemotactic effect to ameliorate paraquat-induced pulmonary fibrosis

Nestin+ Mesenchymal Stromal Cells Fibrotic Transition Mediated by CD169+ Macrophages in Bone Marrow Chronic Graft-versus-Host Disease

Chronic graft-versus-host disease (cGVHD) involves multiple organs, but little is known about bone marrow (BM) alterations caused by cGVHD. In mice and humans, we found that cGVHD is associated with BM fibrosis resulting in T cell infiltration, IgG deposition, and hematopoietic dysfunction. Macrophages and Nestin+ mesenchymal stromal cells (MSCs) participated in the process of BM fibrosis during BM cGVHD development. BM macrophage numbers were significantly increased in mice and humans with BM fibrosis associated with cGVHD. Amplified macrophages produced TGF-β1, which recruited Nestin+ MSCs forming clusters, and Nestin+ MSCs later differentiated into fibroblasts, a process mediated by increased TGF-β/Smad signaling. TLR4/MyD88-mediated activation of endoplasmic reticulum (ER) stress in macrophages is associated with fibrosis by increasing Nestin+ MSC migration and differentiation into fibroblasts. Depletion of macrophages by clodronate-containing liposomes and inhibition of ER stress by 4-phenylbutyric acid reversed BM fibrosis by inhibiting fibroblast differentiation. These studies provide insights into the pathogenesis of BM fibrosis during cGVHD development.

CXCL12/CXCR4: An amazing challenge and opportunity in the fight against fibrosis

Fibrosis is a pathological process caused by abnormal wound healing response, which often leads to excessive deposition of extracellular matrix, distortion of organ architecture, and loss of organ function. Aging is an important risk factor for the development of organ fibrosis. C-X-C receptor 4 (CXCR4) is the predominant chemokine receptor on fibrocytes, C-X-C motif ligand 12 (CXCL12) is the only ligand of CXCR4. Accumulated evidence have confirmed that CXCL12/CXCR4 can be involved in multiple pathological mechanisms in fibrosis, such as inflammation, immunity, epithelial-mesenchymal transition, and angiogenesis. In addition, CXCL12/CXCR4 have also been shown to improve fibrosis levels in many organs including the heart, liver, lung and kidney; thus, they are promising targets for anti-fibrotic therapy. Notably, inhibitors of CXCL12 or CXCR4 also play an important role in various fibrosis-related diseases. In summary, this review systematically summarizes the role of CXCL12/CXCR4 in fibrosis, and this information is of great significance for understanding CXCL12/CXCR4. This will also contribute to the design of further studies related to CXCL12/CXCR4 and fibrosis, and shed light on potential therapies for fibrosis.

C-X-C-Chemokine-Receptor-Type-4 Inhibitor AMD3100 Attenuates Pulmonary Inflammation and Fibrosis in Silicotic Mice

Background

Silicosis is a severe pulmonary disease caused by inhaling dust containing crystalline silica. The progression of silicosis to pulmonary fibrosis is usually unavoidable. Recent studies have revealed positivity for the overexpression of C-X-C chemokine receptor type 4 (CXCR4) in pulmonary fibrosis and shown that the CXCR4 inhibitor AMD3100 attenuated pulmonary fibrosis after bleomycin challenge and paraquat exposure. However, it is unclear whether AMD3100 reduces crystalline silica-induced pulmonary fibrosis.

Methods

C57BL/6 male mice were instilled intranasally with a single dose of crystalline silica (12 mg/60 μL) to establish an acute silicosis mouse model. Twelve hours later, the mice were injected intraperitoneally with 5 mg/kg AMD3100 or control solution. Then, the mice were weighed daily and sacrificed on day 7, 14, or 28 to collect lung tissue and peripheral blood. Western blotting was also applied to determine the level of CXCR4, while different histological techniques were used to assess pulmonary inflammation and fibrosis. In addition, the level of B cells in peripheral blood was measured by flow cytometry.

Results

CXCR4 and its ligand CXCL12 were upregulated in the lung tissues of crystalline silica-exposed mice. Blocking CXCR4 with AMD3100 suppressed the upregulation of CXCR4/CXCL12, reduced the severity of lung injury, and prevented weight loss. It also inhibited neutrophil infiltration at inflammatory sites and neutrophil extracellular trap formation, as well as reduced B-lymphocyte aggregates in the lung. Additionally, it decreased the recruitment of circulating fibrocytes (CD45⁺collagen I⁺CXCR4⁺) to the lung and the deposition of collagen I and α-smooth muscle actin in lung tissue. AMD3100 also increased the level of B cells in peripheral blood, preventing circulating B cells from migrating to the injured lungs.

Conclusion

Blocking CXCR4 with AMD3100 delays pulmonary inflammation and fibrosis in a silicosis mouse model, suggesting the potential of AMD3100 as a drug for treating silicosis.

Nestin-Expressing Cells in the Lung: The Bad and the Good Parts

Nestin is a member of the intermediate filament family, which is expressed in a variety of stem or progenitor cells as well as in several types of malignancies. Nestin might be involved in tissue homeostasis or repair, but its expression has also been associated with processes that lead to a poor prognosis in various types of cancer. In this article, we review the literature related to the effect of nestin expression in the lung. According to most of the reports in the literature, nestin expression in lung cancer leads to an aggressive phenotype and resistance to chemotherapy as well as radiation treatments due to the upregulation of phenomena such as cell proliferation, angiogenesis, and metastasis. Furthermore, nestin may be involved in the pathogenesis of some non-cancer-related lung diseases. On the other hand, evidence also indicates that nestin-positive cells may have a role in lung homeostasis and be capable of generating various types of lung tissues. More research is necessary to establish the true value of nestin expression as a prognostic factor and therapeutic target in lung cancer in addition to its usefulness in therapeutic approaches for pulmonary diseases.

Micellar Hyaluronidase and Spiperone as a Potential Treatment for Pulmonary Fibrosis

Concentration of hyaluronic acid (HA) in the lungs increases in idiopathic pulmonary fibrosis (IPF). HA is involved in the organization of fibrin, fibronectin, and collagen. HA has been proposed to be a biomarker of fibrosis and a potential target for antifibrotic therapy. Hyaluronidase (HD) breaks down HA into fragments, but is a subject of rapid hydrolysis. A conjugate of poloxamer hyaluronidase (pHD) was prepared using protein immobilization with ionizing radiation. In a model of bleomycin-induced pulmonary fibrosis, pHD decreased the level of tissue IL-1β and TGF-β, prevented the infiltration of the lung parenchyma by CD16⁺ cells, and reduced perivascular and peribronchial inflammation. Simultaneously, a decrease in the concentrations of HA, hydroxyproline, collagen 1, total soluble collagen, and the area of connective tissue in the lungs was observed. The effects of pHD were significantly stronger compared to native HD which can be attributed to the higher stability of pHD. Additional spiperone administration increased the anti-inflammatory and antifibrotic effects of pHD and accelerated the regeneration of the damaged lung. The potentiating effects of spiperone can be explained by the disruption of the dopamine-induced mobilization and migration of fibroblast progenitor cells into the lungs and differentiation of lung mesenchymal stem cells (MSC) into cells of stromal lines. Thus, a combination of pHD and spiperone may represent a promising approach for the treatment of IPF and lung regeneration.

The effects of carbon monoxide releasing molecules on paraquat-induced pulmonary interstitial inflammation and fibrosis

Paraquat, an herbicide used extensively worldwide, can cause severe toxicity in humans and animals, leading to irreversible, lethal lung fibrosis. The potential of CO-releasing molecules (CORMs), substances that release CO (Carbon monoxide) within animal tissues, for treating paraquat-induced ROS generation and inflammation is investigated here. Our results show that the fast CO releaser CORM-3 (4-20 μM) acts as a potential scavenger of free radicals and decreases fibrosis progression by inhibiting paraquat-induced overexpression of connective tissue growth factor and angiotensin II in MRC-5 cells. The slow CO releaser CORM-A1 (5 mg/kg) clearly decreased expression of the lung profibrogenic cytokines COX-2, TNF-α, and α-SMA and serum hydroxyproline, resulting in a lower mortality rate in paraquat-treated mice. Mice treated with higher-dose CORM-A1 (10 mg/kg) had relatively intact lung lobes and fewer fibrotic patches by gross observation, with less collagen deposition, mesangial matrix accumulation, and pulmonary fibrosis resulting from the mitigation of TGF-β overexpression. In conclusion, our data demonstrate for the first time that CORM-A1 alleviated the development of the fibrotic process and improved survival rate in mice exposed to PQ, would be an attractive therapeutic approach to attenuate the progression of pulmonary fibrosis following PQ exposure.

The herbicide paraquat-induced molecular mechanisms in the development of acute lung injury and lung fibrosis

The herbicide paraquat (PQ; 1,1'-dimethyl-4,4'-bipyridylium dichloride) is a highly toxic organic heterocyclic herbicide that has been widely used in agricultural settings. Since its commercial introduction in the early 1960s, numerous cases of fatal PQ poisonings attributed to accidental and/or intentional ingestion of PQ concentrated formulations have been reported. The clinical manifestations of the respiratory system during the acute phase of PQ poisoning mainly include acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), followed by pulmonary fibrosis in a later phase. The focus of this review is to summarize the most recent publications related to PQ-induced lung toxicity as well as the underlying molecular mechanisms for PQ-mediated pathologic processes. Growing sets of data from in vitro and in vivo models have demonstrated the involvement of the PQ in regulating lung oxidative stress, inflammatory response, epigenetics, apoptosis, autophagy, and the progression of lung fibrosis. The article also summarizes novel therapeutic avenues based on a literature review, which can be explored as potential means to combat PQ-induced lung toxicity. Finally, we also presented clinical studies on the association of PQ exposure with the incidence of lung injury and pulmonary fibrosis.

8-Formylophiopogonanone B Antagonizes Paraquat-Induced Hepatotoxicity by Suppressing Oxidative Stress

Flavonoids are some of the most important natural products with a variety of physiological activities. 8-Formylophiopogonanone B (8-FOB) is a naturally existing homoisoflavonoid in Ophiopogon japonicus. Paraquat (PQ) has been widely used as a potent herbicide and has high toxicity in humans. The goal of the present study was to investigate whether 8-FOB could protect against PQ-induced hepatotoxicity in vitro and in vivo. We first tested the protective effects of 8-FOB on PQ-induced cytotoxicity in L02 cells by determining cell viability, intracellular oxidative stress levels, mitochondrial function, and apoptosis in vitro. To verify the protective effects of 8-FOB, we pretreated mice with 8-FOB and assessed liver function, hepatic oxidative stress, and histopathological changes after PQ administration. Our results revealed that 8-FOB could antagonize PQ-induced hepatotoxicity in vitro and in vivo. The antagonistic effects could be attributed to suppressing oxidative stress, preserving mitochondrial function, and inhibiting apoptosis. The present study is the first to document that 8-FOB, a homoisoflavonoid compound, is an effective antioxidant for antagonizing PQ-induced hepatotoxicity.