M2 macrophage accumulation contributes to pulmonary fibrosis, vascular dilatation, and hypoxemia in rat hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) markedly increases the mortality of patients. However, its pathogenesis remains incompletely understood. Rat HPS develops in common bile duct ligation (CBDL)-induced, but not thioacetamide (TAA)-induced cirrhosis. We investigated the mechanisms of HPS by comparing these two models. Pulmonary histology, blood gas exchange, and the related signals regulating macrophage accumulation were assessed in CBDL and TAA rats. Anti-polymorphonuclear leukocyte (antiPMN) and anti-granulocyte-macrophage colony stimulating factor (antiGM-CSF) antibodies, clodronate liposomes (CL), and monocyte chemoattractant protein 1 (MCP1) inhibitor (bindarit) were administrated in CBDL rats, GM-CSF, and MCP1 were administrated in bone marrow-derived macrophages (BMDMs). Pulmonary inflammatory cell recruitment, vascular dilatation, and hypoxemia were progressively developed by 1 week after CBDL, but only occurred at 4 week after TAA. Neutrophils were the primary inflammatory cells within 3 weeks after CBDL and at 4 week after TAA. M2 macrophages were the primary inflammatory cells, meantime, pulmonary fibrosis, GM-CSFR, and CCR2 were specifically increased from 4 week after CBDL. AntiPMN antibody treatment decreased neutrophil and macrophage accumulation, CL or the combination of antiGM-CSF antibody and bindarit treatment decreased macrophage recruitment, resulting in pulmonary fibrosis, vascular dilatation, and hypoxemia in CBDL rats alleviated. The combination treatment of GM-CSF and MCP1 promoted cell migration, M2 macrophage differentiation, and transforming growth factor-β1 (TGF-β1) production in BMDMs. Conclusively, our results highlight neutrophil recruitment mediates pulmonary vascular dilatation and hypoxemia in the early stage of rat HPS. Further, M2 macrophage accumulation induced by GM-CSF/GM-CSFR and MCP1/CCR2 leads to pulmonary fibrosis and promotes vascular dilatation and hypoxemia, as a result, HPS develops.

A central role for CD68(+) macrophages in hepatopulmonary syndrome. Reversal by macrophage depletion

RATIONALE

The etiology of hepatopulmonary syndrome (HPS), a common complication of cirrhosis, is unknown. Inflammation and macrophage accumulation occur in HPS; however, their importance is unclear. Common bile duct ligation (CBDL) creates an accepted model of HPS, allowing us to investigate the cause of HPS.

OBJECTIVES

We hypothesized that macrophages are central to HPS and investigated the therapeutic potential of macrophage depletion.

METHODS

Hemodynamics, alveolar-arterial gradient, vascular reactivity, and histology were assessed in CBDL versus sham rats (n = 21 per group). The effects of plasma on smooth muscle cell proliferation and endothelial tube formation were measured. Macrophage depletion was used to prevent (gadolinium) or regress (clodronate) HPS. CD68(+) macrophages and capillary density were measured in the lungs of patients with cirrhosis versus control patients (n = 10 per group).

MEASUREMENTS AND MAIN RESULTS

CBDL increased cardiac output and alveolar-arterial gradient by causing capillary dilatation and arteriovenous malformations. Activated CD68(+)macrophages (nuclear factor-κB+) accumulated in HPS pulmonary arteries, drawn by elevated levels of plasma endotoxin and lung monocyte chemoattractant protein-1. These macrophages expressed inducible nitric oxide synthase, vascular endothelial growth factor, and platelet-derived growth factor. HPS plasma increased endothelial tube formation and pulmonary artery smooth muscle cell proliferation. Macrophage depletion prevented and reversed the histological and hemodynamic features of HPS. CBDL lungs demonstrated increased medial thickness and obstruction of small pulmonary arteries. Nitric oxide synthase inhibition unmasked exaggerated pulmonary vasoconstrictor responses in HPS. Patients with cirrhosis had increased pulmonary intravascular macrophage accumulation and capillary density.

CONCLUSIONS

HPS results from intravascular accumulation of CD68(+)macrophages. An occult proliferative vasculopathy may explain the occasional transition to portopulmonary hypertension. Macrophage depletion may have therapeutic potential in HPS.

[The therapeutic effects of tumor necrosis factor-alpha monoclonal antibody on hepatopulmonary syndrome in rats]

AIM

To investigate the therapeutic effects of tumor necrosis factor-alpha monoclonal antibody on hepatopulmonary syndrome in rats.

METHODS

60 adult male Sprague-Dawley rats, weighing 250+/-25 g, were randomly divided into 3 groups: sham operation (6 rats) group, CBDL (30 rats) group and CBDL+TNF-alpha mAb (24 rats) group. Then CBDL operation group was divided into 5 subgroups and the CBDL+TNF-alpha mAb group was divided into 4 subgroups. Then the rats were sacrificed and the liver tissues were removed, then HE and Masson staining was performed to observe the extent of fibrosis. The arterial blood were gotten for analysis of blood gas and observing the change of alveoloarterial oxygen difference. The change of liver function, the concentration of endotoxin, TNF-alpha and NO were detected.

RESULTS

Compared with the CBDL group, the alveoloarterial oxygen difference decreased significantly in CBDL+TNF-alpha mAb group. And the serum levels of ALT, TBIL decreased obviously. The concentration of ETX, TNF-alpha and NO in CBDL+TNF-alpha mAb group were significantly lower than those in CBDL group.

CONCLUSION

There are some therapeutic effects of tumor necrosis factor-alpha antibody on hepatopulmonary syndrome in rats.

Celiac disease associated with nodular regenerative hyperplasia, pulmonary abnormalities, and IgA anticardiolipin antibodies

The association of nodular regenerative hyperplasia with celiac disease is not as well established as it is with hepatopulmonary syndrome and portopulmonary hypertension. IgA anticardiolipin antibodies were reported recently in celiac patients with nodular regenerative hyperplasia. The subject of this study was the description of pulmonary abnormalities and IgA anticardiolipin antibodies in celiac patients with noncirrhotic portal hypertension. Five patients with portal hypertension were investigated to diagnose its etiology. Celiac disease was diagnosed by means of autoantibody reactivity and duodenal biopsies. Liver histology revealed nodular regenerative hyperplasia in four patients and suggested its presence in 1 case. Two cyanotic patients had severe hypoxemia with a confirmed diagnosis of hepatopulmonary syndrome. Another case exhibited features of hepatopulmonary syndrome with increased levels of arterial pulmonary pressure. The remaining 2 cases had slight abnormalities of arterial oxygenation. Three patients had reactivity to IgA anticardiolipin antibodies. The concomitance of celiac disease and nodular regenerative hyperplasia, two infrequent conditions, raises suspicion of there being a nonfortuitous coincidence. Pulmonary abnormalities, and especially hepatopulmonary syndrome, are described for the first time in association with celiac disease and nodular regenerative hyperplasia.

Interleukin-10 inhibits pulmonary NF-kappaB activation and lung injury induced by hepatic ischemia-reperfusion

Hepatic ischemia and reperfusion cause local and remote organ injury. This injury culminates from an integrated cascade of proinflammatory cytokines, chemokines, and adhesion molecules, many of which are regulated by the transcription factor nuclear factor-kappaB (NF-kappaB). The anti-inflammatory cytokine interleukin-10 (IL-10) has been shown to have inhibitory effects on NF-kappaB. The objective of the current study was to determine whether IL-10 could suppress pulmonary NF-kappaB activation and ensuing lung injury induced by hepatic ischemia-reperfusion. C57BL/6 mice underwent partial hepatic ischemia with or without intravenous administration of IL-10. Hepatic ischemia-reperfusion resulted in pulmonary NF-kappaB activation, increased mRNA expression of tumor necrosis factor-alpha (TNF-alpha), and macrophage inflammatory protein-2 (MIP-2), as well as increased pulmonary neutrophil accumulation and lung edema. Administration of IL-10 suppressed lung NF-kappaB activation, reduced TNF-alpha and MIP-2 mRNA expression, and decreased pulmonary neutrophil recruitment and lung injury. The data suggest that IL-10 protects against hepatic ischemia and reperfusion-induced lung injury by inhibiting lung NF-kappaB activation and the resulting pulmonary production of proinflammatory mediators.