Macrophage migration inhibitory factor contributes to hypoxic pulmonary vasoconstriction in rats

Inflammation and immunity in the pathogenesis of hypoxic pulmonary hypertension

Hypoxic pulmonary hypertension (HPH) is a complicated vascular disorder characterized by diverse mechanisms that lead to elevated blood pressure in pulmonary circulation. Recent evidence indicates that HPH is not simply a pathological syndrome but is instead a complex lesion of cellular metabolism, inflammation, and proliferation driven by the reprogramming of gene expression patterns. One of the key mechanisms underlying HPH is hypoxia, which drives immune/inflammation to mediate complex vascular homeostasis that collaboratively controls vascular remodeling in the lungs. This is caused by the prolonged infiltration of immune cells and an increase in several pro-inflammatory factors, which ultimately leads to immune dysregulation. Hypoxia has been associated with metabolic reprogramming, immunological dysregulation, and adverse pulmonary vascular remodeling in preclinical studies. Many animal models have been developed to mimic HPH; however, many of them do not accurately represent the human disease state and may not be suitable for testing new therapeutic strategies. The scientific understanding of HPH is rapidly evolving, and recent efforts have focused on understanding the complex interplay among hypoxia, inflammation, and cellular metabolism in the development of this disease. Through continued research and the development of more sophisticated animal models, it is hoped that we will be able to gain a deeper understanding of the underlying mechanisms of HPH and implement more effective therapies for this debilitating disease.

Respiratory viruses and postoperative hemodynamics in patients with unrestrictive congenital cardiac communications: a prospective cohort study

BACKGROUND

Pulmonary vascular abnormalities pose a risk for severe life-threatening hemodynamic disturbances following surgical repair of congenital cardiac communications (CCC_s). In the distal lung, small airways and vessels share a common microenvironment, where biological crosstalks take place. Because respiratory cells infected by viruses express a number of molecules with potential impact on airway and vascular remodeling, we decided to test the hypothesis that CCC patients carrying viral genomes in the airways might be at a higher risk for pulmonary (and systemic) hemodynamic disturbances postoperatively.

METHODS

Sixty patients were prospectively enrolled (age 11 [7-16] months, median with interquartile range). Preoperative pulmonary/systemic mean arterial pressure ratio (PAP/SAP) was 0.78 (0.63-0.88). The presence or absence of genetic material for respiratory viruses in nasopharyngeal and tracheal aspirates was investigated preoperatively in the absence of respiratory symptoms using real-time polymerase chain reaction (kit for detection of 19 pathogens). Post-cardiopulmonary bypass (CPB) inflammatory reaction was analyzed by measuring serum levels of 36 inflammatory proteins (immunoblotting) 4 h after its termination. Postoperative hemodynamics was assessed using continuous recording of PAP and SAP with calculation of PAP/SAP ratio.

RESULTS

Viral genomes were detected in nasopharynx and the trachea in 64% and 38% of patients, respectively. Rhinovirus was the most prevalent agent. The presence of viral genomes in the trachea was associated with an upward shift of postoperative PAP curve (p = 0.011) with a PAP/SAP of 0.44 (0.36-0.50) in patients who were positive versus 0.34 (0.30-0.45) in those who were negative (p = 0.008). The presence or absence of viral genomes in nasopharynx did not help predict postoperative hemodynamics. Postoperative PAP/SAP was positively correlated with post-CPB levels of interleukin-1 receptor antagonist (p = 0.026), macrophage migration inhibitory factor (p = 0.019) and monocyte chemoattractant protein-1 (p = 0.031), particularly in patients with virus-positive tracheal aspirates.

CONCLUSIONS

Patients with CCC_s carrying respiratory viral genomes in lower airways are at a higher risk for postoperative pulmonary hypertension, thus deserving special attention and care. Preoperative exposure to respiratory viruses and post-CPB inflammatory reaction seem to play a combined role in determining the postoperative behavior of the pulmonary circulation.

Elevated concentrations of macrophage migration inhibitory factor in serum and cerebral microdialysate are associated with delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Objective

Inflammation is increasingly recognized to be involved in the pathophysiology of aneurysmal subarachnoid hemorrhage (aSAH) and may increase the susceptibility to delayed cerebral ischemia (DCI). Macrophage migration inhibitory factor (MIF) has been shown to be elevated in serum and cerebrospinal fluid (CSF) after aSAH. Here, we determined MIF levels in serum, CSF and cerebral microdialysate (MD) at different time-points after aSAH and evaluated their clinical implications.

Methods

MIF levels were measured in serum, CSF and MD obtained from 30 aSAH patients during early (EP_d1-4), critical (CP_d5-15) and late (LP_d16-21) phase after hemorrhage. For subgroup analyses, patients were stratified based on demographic and clinical data.

Results

MIF levels in serum increased during CP_d5-15 and decreased again during LP_d16-21, while CSF levels showed little changes over time. MD levels peaked during EP_d1-4, decreased during CP_d5-15 and increased again during LP_d16-21. Subgroup analyses revealed significantly higher serum levels in patients with aneurysms located in the anterior vs. posterior circulation during CP_d5-15 (17.3 [15.1-21.1] vs. 10.0 [8.4-11.5] ng/ml, p = 0.009) and in patients with DCI vs. no DCI during CP_d5-15 (17.9 [15.1-22.7] vs. 11.9 [8.9-15.9] ng/ml, p = 0.026) and LP_d16-21 (17.4 [11.7-27.9] vs. 11.3 [9.2-12.2] ng/ml, p = 0.021). In addition, MIF levels in MD during CP_d5-15 were significantly higher in patients with DCI vs. no DCI (3.6 [1.8-10.7] vs. 0.2 [0.1-0.7] ng/ml, p = 0.026), while CSF levels during the whole observation period were similar in all subgroups.

Conclusion

Our findings in a small cohort of aSAH patients provide preliminary data on systemic, global cerebral and local cerebral MIF levels after aSAH and their clinical implications.

Clinical trial registration

ClinicalTrials.gov, identifier: NCT02142166.

Postoperative Pulmonary Hemodynamics and Systemic Inflammatory Response in Pediatric Patients Undergoing Surgery for Congenital Heart Defects

There is scarce information about the relationships between postoperative pulmonary hemodynamics, inflammation, and outcomes in pediatric patients with congenital cardiac communications undergoing surgery. We prospectively studied 40 patients aged 11 (8–17) months (median with interquartile range) with a preoperative mean pulmonary arterial pressure of 48 (34–54) mmHg who were considered to be at risk for postoperative pulmonary hypertension. The immediate postoperative pulmonary/systemic mean arterial pressure ratio (PAP/SAP_IPO, mean of first 4 values obtained in the intensive care unit, readings at 2-hour intervals) was correlated directly with PAP/SAP registered in the surgical room just after cardiopulmonary bypass (r = 0.68, p < 0.001). For the entire cohort, circulating levels of 15 inflammatory markers changed after surgery. Compared with patients with PAP/SAP_IPO ≤ 0.40 (n = 22), those above this level (n = 18) had increased pre- and postoperative serum levels of granulocyte colony-stimulating factor (p = 0.040), interleukin-1 receptor antagonist (p = 0.020), interleukin-6 (p = 0.003), and interleukin-21 (p = 0.047) (panel for 36 human cytokines) and increased mean platelet volume (p = 0.018). Using logistic regression analysis, a PAP/SAP_IPO > 0.40 and a heightened immediate postoperative serum level of macrophage migration inhibitory factor (quartile analysis) were shown to be predictive of significant postoperative cardiopulmonary events (respective hazard ratios with 95% CIs, 5.07 (1.10–23.45), and 3.29 (1.38–7.88)). Thus, the early postoperative behavior of the pulmonary circulation and systemic inflammatory response are closely related and can be used to predict outcomes in this population.

Cytokines, Chemokines, and Inflammation in Pulmonary Arterial Hypertension

According to the World Symposium Pulmonary Hypertension (WSPH) classification, pulmonary hypertension (PH) is classified into five categories based on etiology. Among them, Group 1 pulmonary arterial hypertension (PAH) disorders are rare but progressive and often, fatal despite multiple approved treatments. Elevated pulmonary arterial pressure in patients with WSPH Group 1 PAH is mainly caused by increased pulmonary vascular resistance (PVR), due primarily to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Growing evidence indicates that inflammation plays a critical role in the development of pulmonary vascular remodeling associated with PAH. While the role of auto-immunity is unclear, infiltration of inflammatory cells in and around vascular lesions, including T- and B-cells, dendritic cells, macrophages, and mast cells have been observed in PAH patients. Serum and plasma levels of chemokines, cytokines, and autoantibodies are also increased in PAH patients; some of these circulating molecules are correlated with disease severity and survival. Preclinical experiments have reported a key role of the inflammation in PAH pathophysiology in vivo. Importantly, anti-inflammatory and immunosuppressive agents have further exhibited therapeutic effects. The present chapter reviews published experimental and clinical evidence highlighting the canonical role of inflammation in the pathogenesis of PAH and as a major target for the development of anti-inflammatory therapies in patients with PAH.

Cerebrospinal fluid macrophage migration inhibitory factor: a potential predictor of cerebral vasospasm and clinical outcome after aneurysmal subarachnoid hemorrhage

OBJECTIVE

In patients with aneurysmal subarachnoid hemorrhage (aSAH), poor outcomes have been shown to be correlated with subsequent cerebral vasospasm (CV) and delayed cerebral ischemia (DCI). The identification of novel biomarkers may aid in the prediction of which patients are vulnerable to developing vasospasm, cerebral ischemia, and neurological deterioration.

METHODS

In this prospective clinical study at North Shore University Hospital, patients with aSAH or normal pressure hydrocephalus (NPH) with external ventricular drains were enrolled. The concentration of macrophage migration inhibitory factor (MIF) in CSF was assessed for correlation with CV or DCI, the primary outcome measures.

RESULTS

Twenty-five patients were enrolled in the aSAH group and 9 were enrolled in the NPH group. There was a significant increase in aggregate CSF MIF concentration in patients with aSAH versus those with NPH (24.4 ± 19.2 vs 2.3 ± 1.1 ng/ml, p < 0.0002). Incidence of the day of peak MIF concentration significantly correlated with the onset of clinical vasospasm (rho = 0.778, p < 0.0010). MIF concentrations were significantly elevated in patients with versus those without evidence of DCI (18.7 ± 4.93 vs 8.86 ± 1.28 ng/ml, respectively, p < 0.0025). There was a significant difference in MIF concentrations between patients with infection versus those without infection (16.43 ± 4.21 vs 8.5 ± 1.22 ng/ml, respectively, p < 0.0119).

CONCLUSIONS

Preliminary evidence from this study suggests that CSF concentrations of MIF are correlated with CV and DCI. These results, however, could be confounded in the presence of clinical infection. A study with a larger patient sample size is necessary to corroborate these findings.

Macrophage migration inhibitory factor and chemokine RANTES in young pediatric patients with congenital cardiac communications: Relation to hemodynamic parameters and the presence of Down syndrome

Inflammation and immunity are central in the pathobiology of pulmonary vascular disorders. Preliminary headway has been made in understanding the relationships between inflammatory proteins and clinical parameters in pediatric congenital heart disease. In this study, we analyzed serum levels of macrophage migration inhibitory factor (MIF) and regulated on activation normal T cell expressed and secreted chemokine (RANTES) in 87 patients with unrestrictive congenital cardiac communications and signs of pulmonary hypertension (age 2-36 months) and 50 pediatric controls. They were investigated in relation to clinical and hemodynamic parameters and the presence of Down syndrome. Hemodynamics was assessed by transthoracic Doppler echocardiography and cardiac catheterization. Chemokines were analyzed in serum using a chemiluminescence assay. The highest MIF levels were observed in very young subjects with heightened pulmonary vascular resistance but who presented a positive response to vasodilator challenge with inhaled nitric oxide. In contrast, RANTES levels were higher in patients with pulmonary overcirculation and congestion, correlating nonlinearly with pulmonary blood flow. Levels of both chemokines were higher in subjects with Down syndrome than in nonsyndromic individuals, but the difference was observed only in patients, not in the control group. In patients with Down syndrome, there was a direct relationship between preoperative serum MIF and the level of pulmonary artery pressure observed 6 months after surgical repair of cardiac anomalies. Thus, it was interesting to observe that MIF, which is key in the innate immune response and chemokine RANTES, which is highly expressed in respiratory viral infections were related to clinical and hemodynamic abnormalities associated with pediatric congenital heart disease.

Multiple roles of macrophage migration inhibitory factor in pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening condition arising from the loss and obstructive remodeling of the pulmonary arteries, leading to the sustained elevation of pulmonary arterial pressure (PAP) and pulmonary vascular resistance (PVR) and subsequently right ventricular (RV) failure and death. PH encompasses a group of multifactorial diseases, such as pulmonary arterial hypertension (PAH) and chronic thromboembolic PH, for which there is no treatment that can stop or reverse the progression of remodeling of the pulmonary vasculature. The identification of new molecular targets for the development of more effective drugs is thus urgently needed. In this context, macrophage migration inhibitory factor (MIF), a pleiotropic upstream proinflammatory mediator, is emerging as a promising molecular target, as it contributes to perivascular inflammation and pulmonary arterial remodeling, two key hallmarks of PAH that are not specifically targeted by currently approved therapies. The objective of this review is to summarize the scientific evidence on the pathogenic roles of MIF and its potential as a biomarker and therapeutic target in PH/PAH.

Key inflammatory pathways underlying vascular remodeling in pulmonary hypertension

Independent of the underlying cause, pulmonary hypertension (PH) remains a devastating condition that is characterized by limited survival. Cumulating evidence indicates that in addition to a dysbalance of mediators regulating vascular tone and growth factors promoting vascular remodeling, failure to resolve inflammation and altered immune processes play a pivotal role in the development and progression of PH. Here, we highlight the role of key inflammatory pathways in the pathobiology of vascular remodeling and PH, and discuss potential therapeutic interventions that may halt disease progression or even reverse pulmonary vascular remodeling. Perivascular inflammation is present in all forms of PH, and inflammatory pathways involve numerous mediators and cell types including macrophages, neutrophils, T cells, dendritic cells, and mast cells. Dysfunctional bone morphogenic protein receptor 2 (BMPR2) signaling and dysregulated immunity enable the accumulation of macrophages and other inflammatory cells in obliterative vascular lesions. Regulatory T cells (Tregs) were shown to be of particular relevance in the control of inflammatory responses. Key cytokines/chemokines include interleukin-6, functioning via classic or trans-signaling, macrophage migratory inhibitory factor (MIF), but also other mediators such as neutrophil-derived myeloperoxidase. The expanding knowledge on this topic has resulted in multiple opportunities for sophisticated therapeutic interventions.

Transfusion of standard-issue packed red blood cells induces pulmonary vasoconstriction in critically ill patients after cardiac surgery-A randomized, double-blinded, clinical trial

BACKGROUND

Experimental and volunteer studies have reported pulmonary vasoconstriction during transfusion of packed red blood cells (PRBCs) stored for prolonged periods. The primary aim of this study was to evaluate whether transfusion of PRBCs stored over 21 days (standard-issue, siPRBCs) increases pulmonary artery pressure (PAP) to a greater extent than transfusion of PRBCs stored for less then 14 days (fresh, fPRBCs) in critically ill patients following cardiac surgery. The key secondary aim was to assess whether the pulmonary vascular resistance index (PVRI) increases after transfusion of siPRBCs to a greater extent than after transfusion of fPRBCs.

METHODS

The study was performed as a single-center, double-blinded, parallel-group, randomized clinical trial. Leukoreduced PRBCs were transfused while continuously measuring hemodynamic parameters. Systemic concentrations of syndecan-1 were measured to assess glycocalyx injury. After randomizing 19 patients between January 2014 and June 2016, the study was stopped due to protracted patient recruitment.

RESULTS

Of 19 randomized patients, 11 patients were transfused and included in statistical analyses. Eight patients were excluded prior to transfusion, 6 patients received fPRBCs (10±3 storage days), whereas 5 patients received siPRBCs (33±4 storage days). The increase in PAP (7±3 vs. 2±2 mmHg, P = 0.012) was greater during transfusion of siPRBCs than during transfusion of fPRBCs. In addition, the change in PVRI (150±89 vs. -4±37 dyn·s·cm-5·m2, P = 0.018) was greater after transfusion of siPRBCs than after transfusion of fPRBCs. The increase in PAP correlated with the change of systemic syndecan-1 concentrations at the end of transfusion (R = 0.64,P = 0.034).

CONCLUSION

Although this study is underpowered and results require verification in larger clinical trials, our findings suggest that transfusion of siPRBCs increases PAP and PVRI to a greater extent than transfusion of fPRBCs in critically ill patients following cardiac surgery. Glycocalyx injury might contribute to pulmonary vasoconstriction associated with transfusion of stored blood.

Relation of Macrophage Migration Inhibitory Factor to Pulmonary Hemodynamics and Vascular Structure and Carbamyl-Phosphate Synthetase I Genetic Variations in Pediatric Patients with Congenital Cardiac Shunts

Macrophage migration inhibitory factor (MIF) plays an important pathophysiological role in pulmonary hypertension (PHT). Previously, we demonstrated that serum MIF is increased in pediatric PHT associated with congenital heart disease (CHD). In the present study, we determined possible associations between MIF levels, hemodynamic and histological parameters, and mitochondrial carbamyl-phosphate synthetase I (CPSI) T1405N polymorphism in a similar population. The asparagine 1405 variant (related to A alleles in the C-to-A transversion) has been shown to be advantageous in pediatric PHT compared to the threonine 1405 variant (C alleles). Forty-one patients were enrolled (aged 2-36 months) and subsequently divided into 2 groups after diagnostic evaluation: the high-pulmonary blood flow (high PBF) group (pulmonary-to-systemic blood flow ratio 2.58 (2.21-3.01), geometric mean with 95% CI) and the high-pulmonary vascular resistance (high PVR) group (pulmonary vascular resistance 6.12 (4.78-7.89) Wood units × m²). Serum MIF was measured using a chemiluminescence assay. The CPSI polymorphism was analyzed by polymerase chain reaction followed by high-resolution melting analysis. Medial hypertrophy of pulmonary arteries was assessed by the histological examination of biopsy specimens. Serum MIF was elevated in patients compared to controls (p = 0.045), particularly in the high-PVR group (n = 16) (p = 0.022) and in subjects with the AC CPSI T1405N genotype (n = 16) compared to those with the CC genotype (n = 25) (p = 0.017). Patients with high-PVR/AC-genotype profile (n = 9) had the highest MIF levels (p = 0.030 compared with the high-PBF/CC-genotype subgroup, n = 18). In high-PVR/AC-genotype patients, the medial wall thickness of intra-acinar pulmonary arteries was directly related to MIF levels (p = 0.033). There were no patients with the relatively rare AA genotype in the study population. Thus, in the advantageous scenario of the asparagine 1405 variant (AC heterozygosity in this study), heightened pulmonary vascular resistance in CHD-PHT is associated with medial hypertrophy of pulmonary arteries where MIF chemokine very likely plays a biological role.

Expression of macrophage migration inhibitory factor (MIF) in bovine oviducts is higher in the postovulatory phase than during the oestrus and luteal phase

Whether macrophage migration inhibitory factor (MIF) in the bovine oviduct is important for early embryogenesis has not been well substantiated. The aim of the present study was to test the hypothesis that bovine oviduct expresses higher levels of MIF during the post-ovulation phase. Both ampullary and isthmic samples were collected from Japanese black heifers during oestrus (Day 0; n=5), postovulation (Day 3; n=6) and luteal phase (Days 9-12; n=5). MIF mRNA and protein were extracted from the ampullary and isthmic samples and their levels measured by real-time polymerase chain reaction and western blot analysis respectively. Fluorescent immunohistochemistry was performed on frozen ampullary and isthmic sections using antibodies against MIF. MIF mRNA and protein expression was higher in the postovulatory phase than during oestrus and the luteal phase (P<0.05). Fluorescent immunohistochemistry confirmed that in all phases of the oestrous cycle evaluated, the primary site of MIF expression in the ampulla and isthmus was the tunica mucosa. In conclusion, the bovine ampulla and isthmus have higher MIF expression during the postovulatory phase. Further studies are needed to clarify the role of MIF in bovine oviducts.

Macrophage migration inhibitory factor (MIF) in the development and progression of pulmonary arterial hypertension

Macrophage migration inhibitory factor (MIF) has been described as a pro-inflammatory cytokine and regulator of neuro-endocrine function. It plays an important upstream role in the inflammatory cascade by promoting the release of other inflammatory cytokines such as TNF-alpha and IL-6, ultimately triggering a chronic inflammatory immune response. As lungs can synthesize and release MIF, many studies have investigated the potential role of MIF as a biomarker in assessment of patients with pulmonary arterial hypertension (PAH) and using anti-MIFs as a new therapeutic modality for PAH.

[Towards new targets for the treatment of pulmonary arterial hypertension : Importance of cell-cell communications]

Pulmonary arterial hypertension (PAH) is a disorder in which mechanical obstruction of the pulmonary vascular bed is largely responsible for the rise in mean pulmonary arterial pressure (mPAP), resulting in a progressive functional decline despite current available therapeutic options. There are multiple mechanisms predisposing to and/or promoting the aberrant pulmonary vascular remodeling in PAH, and these involve not only altered crosstalk between cells within the vascular wall but also sustained inflammation and dysimmunity, cell accumulation in the vascular wall and excessive activation of some growth factor-stimulated signaling pathways, in addition to the interaction of systemic hormones, local growth factors, cytokines, and transcription factors. Heterozygous germline mutations in the bone morphogenetic protein receptor, type-2 (BMPR2) gene, a gene encoding a receptor for the transforming growth factor (TGF)-β superfamily, can predispose to the disease. Although the spectrum of therapeutic options for PAH has expanded in the last 20 years, available therapies remain essentially palliative. Over the past decade, however, a better understanding of key regulators of this irreversible remodeling of the pulmonary vasculature has been obtained. New and more effective approaches are likely to emerge. The present article profiles the innovative research into novel pathways and therapeutic targets that may lead to the development of targeted agents in PAH.

Ginsenoside Rg1 attenuates hypoxia and hypercapnia-induced vasoconstriction in isolated rat pulmonary arterial rings by reducing the expression of p38

BACKGROUND

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by increased pulmonary arteriolar resistance. Pulmonary vasoconstriction has been proved to play a significant role in PAH. We previously reported that Panax notoginseng saponins (PNS) might attenuate hypoxia and hypercapnia-induced pulmonary vasoconstriction (HHPV).

METHODS

In the present study, our specific objective was to investigate the role of ginsenoside Rg1, a major component of PNS, in this process and the possible underlying mechanism. The second order pulmonary rings isolated from the Sprague-Dawley rats were treated with different dosage of ginsenoside Rg1 at 8, 40, or 100 mg/L respectively, both before and during the conditions of hypoxia and hypercapnia. Contractile force changes of the rings were detected. Furthermore, SB203580, the selective inhibitor for p38 activation was applied to the rings. Pulmonary arterial smooth muscle cells (PASMCs) were cultured under hypoxic and hypercapnic conditions, and ginsenoside Rg1 was administered to detect the changes induced by p38.

RESULTS

Under the hypoxic and hypercapnic conditions, we observed a biphasic pulmonary artery contractile response to the second pulmonary artery rings. It is hypothesized that the observed attenuation of vasoconstriction and the production of vasodilation could have been induced by ginsenoside Rg1. This effect was significantly reinforced by SB203580 (P<0.05 or P<0.01). The expression of p38 in the PASMCs under hypoxic and hypercapnic conditions was significantly activated (P<0.05 or P<0.01) and the observed activation was attenuated by ginsenoside Rg1 (P<0.05 or P<0.01).

CONCLUSIONS

Our findings strongly support the significant role of ginsenoside Rg1 in the inhibition of hypoxia and hypercapnia-induced vasoconstriction by the p38 pathway.

Macrophage Migration Inhibitor Factor Upregulates MCP-1 Expression in an Autocrine Manner in Hepatocytes during Acute Mouse Liver Injury

Macrophage migration inhibitor factor (MIF), a multipotent innate immune mediator, is an upstream component of the inflammatory cascade in diseases such as liver disease. Monocyte chemoattractant protein-1 (MCP-1), a highly representative chemokine, is critical in liver disease pathogenesis. We investigated the role of MIF in regulating hepatocytic MCP-1 expression. MIF and MCP-1 expression were characterized by immunochemistry, RT-PCR, ELISA, and immunoblotting in CCl₄-treated mouse liver and isolated hepatocytes. MIF was primarily distributed in hepatocytes, and its expression increased upon acute liver injury. Its expression was also increased in injured hepatocytes, induced by LPS or CCl₄, which mimic liver injury in vitro. MIF was expressed earlier than MCP-1, strongly inducing hepatocytic MCP-1 expression. Moreover, the increase in MCP-1 expression induced by MIF was inhibited by CD74- or CD44-specific siRNAs and SB203580, a p38 MAPK inhibitor. Further, CD74 or CD44 deficiency effectively inhibited MIF-induced p38 activation. MIF inhibitor ISO-1 reduced MCP-1 expression and p38 phosphorylation in CCl₄-treated mouse liver. Our results showed that MIF regulates MCP-1 expression in hepatocytes of injured liver via CD74, CD44, and p38 MAPK in an autocrine manner, providing compelling information on the role of MIF in liver injury, and implying a new regulatory mechanism for liver inflammation.

Macrophage Migration Inhibitory Factor in Clinical Kidney Disease

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine implicated in acute and chronic inflammatory conditions, including sepsis, autoimmune disease, atherogenesis, plaque instability, and pulmonary arterial hypertension. MIF in plasma and urine is significantly elevated in patients with acute kidney injury (AKI) and elevated MIF in serum is associated with markers of oxidative stress, endothelial dysfunction, arterial stiffness, and markers of myocardial damage in chronic kidney disease (CKD). Furthermore, MIF seems to be involved in vascular processes and cardiovascular disease associated with CKD, glomerulonephritis, autosomal dominant polycystic kidney disease, and possibly also in progression to renal failure. Moreover, in active anti-neutrophil cytoplasmatic antibody-associated vasculitis, plasma MIF levels have been shown to be significantly elevated as compared with samples from patients in remission. A significant difference in the genotype frequency of high production MIF -173 G/C genotype has been found in end-stage renal disease, compared to controls. Inhibition of MIF in a diabetic nephropathy model ameliorated blood glucose and albuminuria and in a model of adult polycystic kidney disease cyst growth was delayed. Preclinical studies support a potential therapeutic role for MIF in AKI and in a number of CKDs, whereas these data in human disease are still observational. Future interventional studies are needed to delineate the role of MIF as a treatment target in clinical kidney disease.

Iptakalim attenuates hypoxia-induced pulmonary arterial hypertension in rats by endothelial function protection

The present study aimed to investigate the protective effects of iptakalim, an adenosine triphosphate (ATP)-sensitive potassium channel opener, on the inflammation of the pulmonary artery and endothelial cell injury in a hypoxia-induced pulmonary arterial hypertension (PAH) rat model. Ninety-six Sprague-Dawley rats were placed into normobaric hypoxia chambers for four weeks and were treated with iptakalim (1.5 mg/kg/day) or saline for 28 days. The right ventricle systolic pressures (RVSP) were measured and small pulmonary arterial morphological alterations were analyzed with hematoxylin and eosin staining. Enzyme-linked immunosorbent assay (ELISA) was performed to analyze the content of interleukin (IL)-1β and IL-10. Immunohistochemical analysis for ED1(+) monocytes was performed to detect the inflammatory cells surrounding the pulmonary arterioles. Western blot analysis was performed to analyze the expression levels of platelet endothelial cell adhesion molecule-1 (PECAM-1) and endothelial nitric oxide synthase (eNOS) in the lung tissue. Alterations in small pulmonary arteriole morphology and the ultrastructure of pulmonary arterial endothelial cells were observed via light and transmission electron microscopy, respectively. Iptakalim significantly attenuated the increase in mean pulmonary artery pressure, RVSP, right ventricle to left ventricle plus septum ratio and small pulmonary artery wall remodeling in hypoxia-induced PAH rats. Iptakalim also prevented an increase in IL-1β and a decrease in IL-10 in the peripheral blood and lung tissue, and alleviated inflammatory cell infiltration in hypoxia-induced PAH rats. Furthermore, iptakalim enhanced PECAM-1 and eNOS expression and prevented the endothelial cell injury induced by hypoxic stimuli. Iptakalim suppressed the pulmonary arteriole and systemic inflammatory responses and protected against the endothelial damage associated with the upregulation of PECAM-1 and eNOS, suggesting that iptakalim may represent a potential therapeutic agent for PAH.

Inflammation and immunity in the pathogenesis of pulmonary arterial hypertension

This review summarizes an expanding body of knowledge indicating that failure to resolve inflammation and altered immune processes underlie the development of pulmonary arterial hypertension. The chemokines and cytokines implicated in pulmonary arterial hypertension that could form a biomarker platform are discussed. Pre-clinical studies that provide the basis for dysregulated immunity in animal models of the disease are reviewed. In addition, we present therapies that target inflammatory/immune mechanisms that are currently enrolling patients, and discuss others in development. We show how genetic and metabolic abnormalities are inextricably linked to dysregulated immunity and adverse remodeling in the pulmonary arteries.

Oxymatrine prevents hypoxia- and monocrotaline-induced pulmonary hypertension in rats

Pulmonary hypertension is a progressive disease characterized by marked pulmonary arterial remodeling and increased vascular resistance. Inflammation and oxidative stress promote the development of pulmonary hypertension. Oxymatrine, one of the main active components of the Chinese herb Sophora flavescens Ait. (Kushen), plays anti-inflammatory and antioxidant protective roles, which effects on pulmonary arteries remain unclear. This study aimed to investigate the effects of oxymatrine on pulmonary hypertension development. Sprague-Dawley rats were exposed to hypoxia for 28 days or injected with monocrotaline, to develop pulmonary hypertension, along with administration of oxymatrine (50mg/kg/day). Hemodynamics and pulmonary arterial remodeling data from the rats were then obtained. The antiproliferative effect of oxymatrine was verified by in vitro assays. The inflammatory cytokine mRNA levels and leukocyte and T cell accumulation in lung tissue were detected. The antioxidative effects of oxymatrine were explored in vitro. Our study shows that oxymatrine treatment attenuated right-ventricular systolic pressure and pulmonary arterial remodeling induced by hypoxia or monocrotaline and inhibited proliferation of pulmonary arterial smooth muscle cells (PASMCs). Increased expression of inflammatory cytokine mRNA and accumulation of leukocytes and T cells around the pulmonary arteries were suppressed with oxymatrine administration. Under hypoxic conditions, oxymatrine significantly upregulated Nrf2 and antioxidant protein SOD1 and HO-1 expression, but downregulated hydroperoxide levels in PASMCs. In summary, this study indicates that oxymatrine may prevent pulmonary hypertension through its antiproliferative, anti-inflammatory, and antioxidant effects, thus providing a promising pharmacological avenue for treating pulmonary hypertension.

Pulmonary vascular mechanics: important contributors to the increased right ventricular afterload of pulmonary hypertension

Chronic hypoxia causes pulmonary vasoconstriction and vascular remodelling, which lead to hypoxic pulmonary hypertension (HPH). Hypoxic pulmonary hypertension is associated with living at high altitudes and is a complication of many lung diseases, including chronic obstructive pulmonary disease, cystic fibrosis and obstructive sleep apnoea. Pulmonary vascular changes that occur with HPH include stiffening and narrowing of the pulmonary arteries that appear to involve all vascular cell types and sublayers of the arterial wall. Right ventricular (RV) changes that occur with HPH include RV hypertrophy and RV fibrosis, often with preserved systolic and diastolic function and ventricular-vascular coupling efficiency. Both vascular stiffening and vascular narrowing are important contributors to RV afterload via increases in oscillatory and steady ventricular work, respectively. The increased blood viscosity that occurs in HPH can be dramatic and is another important contributor to RV afterload. However, the viscosity, vascular mechanics and ventricular changes that occur with HPH are all reversible. Furthermore, even with continued hypoxia the vascular remodelling does not progress to the obliterative, plexiform lesions that are seen clinically in severe pulmonary hypertension. In animal models, the RV changes appear adaptive, not maladaptive. In summary, HPH-induced vascular mechanical changes affect ventricular function, but both are adaptive and reversible, which differentiates HPH from severe pulmonary hypertension. The mechanisms of adaptation and reversibility may provide useful insight into therapeutic targets for the clinical disease state.