The effect of anti-inflammatory properties of mycophenolate mofetil on the development of lung reperfusion injury

Santos H. Mycophenolic Acid-loaded Naïve Macrophage-derived Extracellular Vesicles Rescue Cardiac Myoblast after Inflammatory Injury

Exosomes are natural endogenous extracellular vesicles with phospholipid-based bilayer membrane structures. Due to their unique protein-decorated membrane properties, exosomes have been regarded as promising drug carriers to deliver small molecules and genes. A number of approaches have been developed for exosome-based drug loading. However, the drug loading capability of exosomes is inconsistent, and the effects of loading methods on the therapeutic efficacy have not been investigated in detail. Herein, we developed anti-inflammatory drug-loaded exosomes as an immunomodulatory nanoplatform. Naïve macrophage-derived exosomes (Mϕ-EVs) were loaded with the anti-inflammatory drug mycophenolic acid (MPA) by three major loading methods. Loading into exosomes significantly enhanced anti-inflammatory and antioxidation effects of MPA in vitro compared to free drugs. These findings provide a scientific basis for developing naïve macrophage-secreted exosomes as drug carriers for immunotherapy.

Mycophenolate mofetil attenuates uterine ischaemia/reperfusion injury in a rat model

This study evaluated the effect of mycophenolate mofetil (MMF) on uterine tissue preservation following ischaemia/reperfusion (I/R) injury. Uterine I/R injury was induced in rats by clamping the lower abdominal aorta and ovarian arteries for 30 min. Group I/R + V (n = 7) received vehicle alone while Group I/R + M (n = 7) received 20 mg/kg/day MMF. Control groups underwent sham surgery and received vehicle (Group C) or 20 mg/kg/day MMF (Group M) (n = 7 for both). Four hours after detorsion, uterine tissue 8-hydroxy-2'-deoxyguanosine (8-OHdG), glutathione, malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD) and serum ischaemia modified albumin (IMA) concentrations were measured. Histopathological analyses were performed. The I/R + M group showed significant reduction in serum IMA and uterine tissue 8-OHdG, MDA and MPO and significant increase in SOD concentrations compared with the I/R + V group, indicating a protective effect against I/R oxidative damage (P = 0.009, P = 0.006, P = 0.002, P = 0.003 and P = 0.009, respectively). Histopathological evaluation revealed MMF treatment resulted in significantly less tissue and cellular damage and apoptosis compared with the I/R + V group. These results indicate MMF is effective in attenuating uterine tissue damage and preventing apoptosis following uterine I/R injury, probably via anti-inflammatory and anti-oxidative action.

Mycophenolate mofetil as an immunomodulatory silver bullet in atherogenesis?

Atherosclerotic vascular disease is a chronic disorder of the vasculature with a substantial impact on society. Although the availability of statins has represented an unparalleled improvement in the treatment of patients with such cardiovascular disease, even more effective measures are required to reverse this disorder with a continuously growing incidence. The classification of atherosclerosis as an inflammatory disorder has prompted the hypothesis that immunomodulation could comprise a novel anti-atherosclerotic strategy. Mycophenolate mofetil (MMF) has various anti-atherogenic effects on major components of the atherosclerotic plaque such as T-lymphocytes, monocytes/macrophages and the endothelium. MMF can inhibit leukocyte recruitment to the subendothelium and the subsequent reduced activation of leukocytes will translate into attenuation of subendothelial crosstalk between T-cells and macrophages. This cascade of events will interrupt the self-perpetuating pro-inflammatory environment within the arterial wall, the hallmark of atherosclerotic vascular disease.

Yes-associated protein (YAP) signaling regulates lipopolysaccharide-induced tissue factor expression in human endothelial cells

BACKGROUND

Sepsis-induced acute lung injury (ALI) is characterized by fibrin deposition, which indicates the local activation of coagulation. Tissue factor (TF), expressed in the pulmonary microvasculature, acts as a critical initiator of blood coagulation and ALI in sepsis. The molecular mechanism of lipopolysaccharide (LPS)-induced TF expression in endothelial cells (ECs), however, has not been determined. In this study, we implicate the Rho-associated protein kinase (ROCK)/Yes associated protein (YAP)/early growth response (Egr-1) signaling pathway in LPS-induced TF expression in vitro and in sepsis-induced ALI in vivo.

METHODS

Human umbilical vein ECs incubated with LPS were pretreated with or without the ROCK inhibitor Y-27632, a YAP small, interfering RNA (siRNA) and an Egr-1 siRNA. ROCK, YAP and Egr-1 signaling-induced protein expression was investigated by Western blot. The LPS-induced activation of YAP was analyzed by an immunofluorescent assay. Furthermore, we intratracheally injected YAP siRNA to assess septic ALI in mice by hematoxylin and eosin staining.

RESULTS

LPS rapidly induced ROCK activation and increased TF expression in ECs. LPS caused YAP shuttling into the nuclei of ECs and combined with Egr-1 via the activation of ROCK. Furthermore, the LPS-mediated TF expression increase was prevented by ROCK inactivation, YAP knockdown and Egr-1 depletion, suggesting that LPS-induced TF expression is closely associated with the ROCK/YAP/Egr-1 signaling pathway in ECs. Finally, an intratracheal injection of YAP siRNA relieved lung injury in septic mice.

CONCLUSION

This study not only suggests that ROCK/YAP/Egr-1 signaling regulates TF expression after stimulation with LPS in ECs, but it also indicates that LPS-induced activation of YAP signaling plays an important role in septic ALI in mice. Our findings provide a new insight into the pathogenic mechanism of TF expression, which is closely linked to septic ALI, and YAP signaling is considered to be a novel target for therapeutic intervention under septic conditions.

Egr-1: new conductor for the tissue repair orchestra directs harmony (regeneration) or cacophony (fibrosis)

Fibroblasts and myofibroblasts are the key effector cells executing physiological tissue repair leading to regeneration on the one hand, and pathological fibrogenesis leading to chronic fibrosing conditions on the other. Recent studies identify the multifunctional transcription factor early growth response-1(Egr-1) as an important mediator of fibroblast activation triggered by diverse stimuli. Egr-1 has potent stimulatory effects on fibrotic gene expression, and aberrant Egr-1 expression or function is associated with animal models of fibrosis and human fibrotic disorders, including emphysema, pulmonary fibrosis, pulmonary hypertension and systemic sclerosis. Pharmacological suppression or genetic targeting of Egr-1 blocks fibrotic responses in vitro and ameliorates experimental fibrosis in the skin and lung. In contrast, Egr-1 appears to act as a negative regulator of hepatic fibrosis in mouse models, suggesting a context-dependent role in fibrosis. The Egr-1-binding protein Nab2 is an endogenous inhibitor of Egr-1-mediated signalling and abrogates the stimulation of fibrotic responses induced by transforming growth factor-β (TGFβ). Moreover, mice deficient in Nab2 show excessive collagen accumulation in the skin. These observations highlight a previously unsuspected fundamental physiological function for the Egr-1-Nab2 signalling axis in regulating fibrogenesis, and suggest that Egr-1 may be a potential novel therapeutic target in human diseases complicated by fibrosis. This review summarizes recent advances in understanding the regulation and complex functional role of Egr-1 and its related proteins and inhibitors in pathological fibrosis.

Egr-1 induces a profibrotic injury/repair gene program associated with systemic sclerosis

Transforming growth factor-ß (TGF-ß) signaling is implicated in the pathogenesis of fibrosis in scleroderma or systemic sclerosis (SSc), but the precise mechanisms are poorly understood. The immediate-early gene Egr-1 is an inducible transcription factor with key roles in mediating fibrotic TGF-ß responses. To elucidate Egr-1 function in SSc-associated fibrosis, we examined change in gene expression induced by Egr-1 in human fibroblasts at the genome-wide level. Using microarray expression analysis, we derived a fibroblast "Egr-1-responsive gene signature" comprising over 600 genes involved in cell proliferation, TGF-ß signaling, wound healing, extracellular matrix synthesis and vascular development. The experimentally derived "Egr-1-responsive gene signature" was then evaluated in an expression microarray dataset comprising skin biopsies from 27 patients with localized and systemic forms of scleroderma and six healthy controls. We found that the "Egr-1 responsive gene signature" was substantially enriched in the "diffuse-proliferation" subset comprising exclusively of patients with diffuse cutaneous SSc (dcSSc) of skin biopsies. A number of Egr-1-regulated genes was also associated with the "inflammatory" intrinsic subset. Only a minority of Egr-1-regulated genes was concordantly regulated by TGF-ß. These results indicate that Egr-1 induces a distinct profibrotic/wound healing gene expression program in fibroblasts that is associated with skin biopsies from SSc patients with diffuse cutaneous disease. These observations suggest that targeting Egr-1 expression or activity might be a novel therapeutic strategy to control fibrosis in specific SSc subsets.

Evidence of an anti-inflammatory effect of mycophenolate mofetil in a murine model of pleurisy

A promising therapeutic approach to reducing inflammation is to inhibit the production of proinflammatory cytokines (e.g., tumor necrosis factor alpha [TNF-α], interleukin 1 beta [IL-1β], vascular endothelial growth factor alpha (VEGF-α), and, as shown more recently, interleukin-17 [IL-17]). In the present study, the authors have demonstrated the anti-inflammatory effects of mycophenolate mofetil (MMF) in in vivo experiments and have investigated the mechanism of action underlying those effects. Oral administration of MMF significantly inhibited leukocyte influx during the first (4 hours) and second (48 hours) phases of inflammation in a mouse model of pleurisy caused by carrageenan (P < .01). As expected, MMF suppressed protein levels of TNF-α, IL-1β, VEGF-α, and IL-17A (P < .01). This inhibitory effect was due to down-regulation of mRNA expression for these proinflammatory cytokines (P < .01). These results provide evidence of MMF-mediated inhibition of proinflammatory cytokines, and these anti-inflammatory effects are assumed to result mainly from the inhibition of the synthesis and release of TNF-α, IL-1β, VEGF-α, and IL-17A from activated leukocytes. These findings suggest that MMF might be an applicable therapeutic in the regulation of the inflammatory response-a response in which the humoral system plays a pivotal role.

Early growth response transcription factors: key mediators of fibrosis and novel targets for anti-fibrotic therapy

Fibrosis is a deregulated and ultimately defective form of tissue repair that underlies a large number of chronic human diseases, as well as obesity and aging. The pathogenesis of fibrosis involves multiple cell types and extracellular signals, of which transforming growth factor-ß (TGF-ß) is pre-eminent. The prevalence of fibrosis is rising worldwide, and to date no agents has shown clinical efficacy in the attenuating or reversing the process. Recent studies implicate the immediate-early response transcription factor Egr-1 in the pathogenesis of fibrosis. Egr-1 couples acute changes in the cellular environment to sustained alterations in gene expression, and mediates a broad spectrum of biological responses to injury and stress. In contrast to other ligand-activated transcription factors such as NF-κB, c-jun and Smad2/3 that undergo post-translational modification such as phosphorylation and nuclear translocation, Egr-1 activity is regulated via its biosynthesis. Aberrant Egr-1 expression or activity is implicated in cancer, inflammation, atherosclerosis, and ischemic injury and recent studies now indicate an important role for Egr-1 in TGF-ß-dependent profibrotic responses. Fibrosis in various animal models and human diseases such as scleroderma (SSc) and idiopathic pulmonary fibrosis (IPF) is accompanied by aberrant Egr-1 expression. Moreover Egr-1 appears to be required for physiologic and pathological connective tissue remodeling, and Egr-1-null mice are protected from fibrosis. As a novel profibrotic mediator, Egr-1 thus appears to be a promising potential target for the development of anti-fibrotic therapies.

In rat renal fibroblasts, mycophenolic acid inhibits proliferation and production of the chemokine CCL2, stimulated by tumour necrosis factor-alpha

BACKGROUND AND PURPOSE

Renal fibroblasts play a pivotal role in the development of tubulointerstitial fibrosis, a condition highly predictive of progression towards end-stage renal disease. The present study investigated the anti-mitogenic and anti-inflammatory effects of an inhibitor of inosine monophosphate dehydrogenase, mycophenolic acid (MPA) and the mechanisms underlying its action in normal rat kidney fibroblasts (49F cells).

EXPERIMENTAL APPROACH

Proliferation of 49F cells was studied by tetrazole 3-(4, 5-dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide (MTT) test, bromodeoxyuridine incorporation and flow cytometry. The cyclins, tumour suppressor genes and phospho-mitogen-activated protein kinases (MAPKs) were semiquantified by immunoblotting. Apoptosis was measured by quantifying the fragmented DNA and the activity of caspase 3. The monocyte chemokine CCL2 was measured by ELISA. The mRNA expression of CCL2 was measured by real-time PCR.

KEY RESULTS

Mycophenolic acid dose-dependently inhibited steady-state proliferation of 49F cells by up-regulation of p21, p27 and p53, in association with a decrease in cyclins D2 and E. Treatment with MPA also triggered apoptosis of 49F cells by activating the caspase 3 cascade. Furthermore, MPA attenuated tumour necrosis factor-alpha-induced CCL2 expression through down-regulation of p38 MAPK, but not that of ERK1/2 or JNK.

CONCLUSIONS AND IMPLICATIONS

The anti-mitogenic and anti-inflammatory effects of MPA were mediated by up-regulation of cell cycle inhibitors and pro-apoptotic signals, and by suppression of p38 MAPK pathway respectively. This dual effect of MPA may form the rationale for animal or clinical trials for the treatment of fibrotic renal diseases.

Sirolimus attenuates reduced-size liver ischemia-reperfusion injury but impairs liver regeneration in rats

BACKGROUND

Evidence has suggested that immunosuppressive drugs impact ischemia-reperfusion injury.

AIMS

The purpose of the present study was to evaluate the effect of sirolimus on hepatic injury and regeneration in a rat reduced-size liver ischemia-reperfusion model.

METHODS

Using a newly developed rat reduced-size liver ischemia-reperfusion injury model, the effects of sirolimus were evaluated by assessing liver cell apoptosis and aspartate aminotransferase, myeloperoxidase, and malondialdehyde levels. In addition, liver regeneration after sirolimus treatment was evaluated by measuring liver weight resumption and by the histological examination of bromodeoxyuridine and proliferating cell nuclear antigen expression.

RESULTS

Sirolimus significantly decreased liver cell apoptosis as well as tissue myeloperoxidase and malondialdehyde levels, but impaired postischemic liver regeneration. Ischemia-reperfusion-induced elevation of aspartate aminotransferase serum levels was significantly decreased by sirolimus.

CONCLUSIONS

Despite an impairment of postischemic liver proliferation, sirolimus demonstrated beneficial amelioration of ischemia-reperfusion-induced liver injury in a reduced-size liver model in rats.

Mycophenolate mofetil reduces alveolar inflammation, acute rejection and graft loss due to bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is still the main complication after lung transplantation. Besides other improvements in post-operative management, newer immunosuppressive regimens might decrease the devastating sequelae of this complication.

METHODS

We compared the prospectively collected data of lung transplant recipients treated either with azathioprine (AZA; n = 48) or mycophenolate mofetil (MMF; n = 108), who underwent regular monthly surveillance bronchoscopies for at least 6 post-operative months.

RESULTS

Patients on MMF had significantly fewer acute (P < 0.001) and recurrent (P < 0.001), as well as less severe rejection episodes (P = 0.01). In addition, MMF significantly reduced the number of alveolar lymphocytes, eosinophils and neutrophils (P < 0.001), and decreased the hemosiderin score reflecting non-specific alveolar-capillary damage (P < 0.001). Although there was no change in the three stages of BOS, there was a trend towards improved survival (P = 0.062) and a significant decrease in graft loss due to BOS (P = 0.049) in patients receiving MMF.

CONCLUSIONS

Immunosuppression with MMF significantly decreased the incidence, severity and recurrence of acute rejection episodes in lung transplant recipients. Parameters of alveolar inflammation and alveolar-capillary damage were also decreased. As a potential consequence, MMF significantly reduced graft loss due to BOS and tended to improve overall survival in these patients.

Antioxidant effects of mycophenolate mofetil in a murine pleurisy model

Generation of oxidative stress induced by reactive oxygen species (ROS) and nitrogen (RNS) is believed to be a primary factor in the etiology of various inflammatory diseases. Although, the process of generation of oxygen species is a physiological event, in the inflammatory process this event is increased and produces large amounts of reactive species that leads to lipid peroxidation and to cell death. Mycophenolate mofetil (MMF) is a drug effective in protecting against chronic allograft failure and recently was introduced as an alternative for the treatment of various inflammatory diseases such as glomerulopathies, systemic lupus erythematosus and systemic vasculitis. Based on studies of the anti-inflammatory effect of MMF the aim of this study was to evaluate the effects of MMF on the inhibition of leukocytes and exudation, as well as myeloperoxidase and some antioxidant enzyme activities using carrageenan-induced pleurisy in mice. Our results showed that MMF significantly decreased leukocyte influx (P<0.01), exudation (P<0.01), superoxide dismutase (P<0.05), catalase (P<0.05), glutathione peroxidase (P<0.01), glutathione S-transferase (P<0.01) activities, levels of lipid peroxidation (P<0.05), as well as myeloperoxidase activity (P<0.05) on both phases (4h and 48h) of the inflammatory response induced by carrageenan into the mice pleural cavity. In conclusion, the anti-inflammatory effect of MMF may be, at least in part, via inhibition of ROS and/or NRS overgeneration, and consequently, attenuating the related oxidative stress.

Essential roles for early growth response transcription factor Egr-1 in tissue fibrosis and wound healing

The early growth response gene (Egr-1) codes for a zinc finger transcription factor that has important roles in the regulation of cell growth, differentiation, and survival. Aberrant Egr-1 expression is implicated in carcinogenesis, inflammation, atherosclerosis, and ischemic injury. We reported previously that normal fibroblasts stimulated by transforming growth factor-ss showed rapid and transient induction of Egr-1. Moreover, we observed that tissue expression of Egr-1 was elevated in patients with scleroderma, which suggests that Egr-1 may be involved in tissue repair and fibrosis. Here, we investigated matrix remodeling and wound healing in mice harboring gain of function or loss of function mutations of Egr-1. Using the model of bleomycin-induced scleroderma, we found that the early influx of inflammatory cells into the skin and lungs, and the subsequent development of fibrosis in these organs, were markedly attenuated in Egr-1 null mice. Furthermore, full-thickness incisional skin wound healing was impaired, and skin fibroblasts lacking Egr-1 showed reduced migration and myofibroblast transdifferentiation in vitro. In contrast, transgenic mice with fibroblast-specific Egr-1 overexpression showed exuberant tissue repair, with enhanced collagen accumulation and increased tensile strength of incisional wounds. Together, these results point to the fundamental role that Egr-1 plays in the regulation of transforming growth factor-ss-dependent physiological and pathological matrix remodeling.

CD4+ T lymphocytes mediate acute pulmonary ischemia-reperfusion injury

OBJECTIVE

Postischemic reperfusion of the lung triggers proinflammatory responses that stimulate injurious neutrophil chemotaxis. We hypothesized that T lymphocytes are recruited and activated during reperfusion and mediate subsequent neutrophil-induced lung ischemia-reperfusion injury.

METHODS

An in vivo mouse model of lung ischemia-reperfusion injury was used. C57BL/6 mice were assigned to either the sham group (left thoracotomy) or 7 study groups that underwent 1-hour left hilar occlusion followed by 1 to 24 hours of reperfusion. After in vivo reperfusion, the lungs were perfused ex vivo with buffer whereby pulmonary function was assessed. Lung vascular permeability, edema, neutrophil accumulation, and cytokine/chemokine production (tumor necrosis factor alpha, interleukin 17, CCL3, and CXCL1) were assessed based on Evans blue dye leak, wet/dry weight ratio, myeloperoxidase level, and enzyme-linked immunosorbent assay, respectively.

RESULTS

A preliminary study showed that 2 hours of reperfusion resulted in greater pulmonary dysfunction than 1 or 24 hours of reperfusion. The 2-hour reperfusion period was thus used for the remaining experiments. Comparable and significant protection from ischemia-reperfusion injury-induced lung dysfunction and injury occurred after antibody depletion of neutrophils or CD4(+) T cells but not CD8(+) T cells (P < .05 vs immunoglobulin G control). Lung ischemia-reperfusion injury was proportional to the infiltration of neutrophils but not T cells. Moreover, pulmonary neutrophil infiltration and the production of CXCL1 (KC) were significantly diminished by CD4(+) T-cell depletion but not vice versa.

CONCLUSIONS

Both CD4(+) T lymphocytes and neutrophils accumulate during reperfusion and contribute sequentially to lung ischemia-reperfusion injury. The data suggest that neutrophils mediate ischemia-reperfusion injury; however, CD4(+) T cells play a critical role in stimulating chemokine production and neutrophil chemotaxis during ischemia-reperfusion injury.

Smad-independent transforming growth factor-beta regulation of early growth response-1 and sustained expression in fibrosis: implications for scleroderma

Transforming growth factor-beta (TGF-beta) plays a key role in scleroderma pathogenesis. The transcription factor early growth response-1 (Egr-1) mediates the stimulation of collagen transcription elicited by TGF-beta and is necessary for the development of pulmonary fibrosis in mice. Here, we report that TGF-beta causes a time- and dose-dependent increase in Egr-1 protein and mRNA levels and enhanced transcription of the Egr-1 gene via serum response elements in normal fibroblasts. The ability of TGF-beta to stimulate Egr-1 was preserved in Smad3-null mice and in explanted Smad3-null fibroblasts. The response was blocked by a specific mitogen-activated protein kinase kinase 1 (MEK1) inhibitor but not by an ALK5 kinase inhibitor. Furthermore, MEK1 was phosphorylated by TGF-beta, which was sufficient to drive Egr-1 transactivation. Stimulation by TGF-beta enhanced the transcriptional activity of Elk-1 via the MEK-extracellular signal-regulated kinase 1/2 pathway. Bleomycin-induced scleroderma in the mouse was accompanied by increased Egr-1 accumulation in lesional fibroblasts. Furthermore, biopsies of lesional skin and lung from patients with scleroderma showed increased Egr-1 levels, which were highest in early diffuse disease. Moreover, both Egr-1 mRNA and protein were elevated in explanted scleroderma skin fibroblasts in vitro. Together, these findings define a Smad-independent TGF-beta signal transduction mechanism that underlies the stimulation of Egr-1, demonstrate for the first time sustained Egr-1 up-regulation in fibrotic lesions and suggests that Egr-1 has a role in the induction and progression of fibrosis.

Clinically relevant immunosuppressants influence UVB-induced tumor size through effects on inflammation and angiogenesis

Immunosuppressive therapies allow long-term patient and transplant survival, but are associated with increased development of UV-induced skin cancers, particularly squamous cell carcinomas. The mechanisms by which CsA, MMF, tacrolimus (TAC) or sirolimus (SRL), alone or in dual combinations, influence tumor development and progression are not completely understood. In the current study, chronically UV-exposed mice treated with SRL alone or in combination with CsA or TAC developed more tumors than mice treated with vehicle or other immunosuppressants, but the tumors were significantly smaller and less advanced. Mice treated with CsA or TAC developed significantly larger tumors than vehicle-treated mice, and a larger percentage in the CsA group were malignant. The addition of MMF to CsA, but not to TAC, significantly reduced tumor size. Immunosuppressant effects on UVB-induced inflammation and tumor angiogenesis may explain these findings. CsA enhanced both UVB-induced inflammation and tumor blood vessel density, while MMF reduced inflammation. Addition of MMF to CsA reduced tumor size and vascularity. SRL did not affect inflammation, but significantly reduced tumor vascularity. Thus the choice of immunosuppressants has important implications for tumor number, size and progression, likely due to the influence of immunosuppressants on UVB-induced inflammation and angiogenesis.

Emerging drugs in lung transplantation

The balance between immunosuppression to ensure graft tolerance while preventing emergence of infectious complications is key in lung transplantation. Although opportunistic infection may appear to be the most important of these complications, malignancies and severe drug toxicities significantly affect the short- and long-term outcomes of the patients. The present practice is combination therapy using drugs with complementary immunosuppressive action, to achieve synergistic immunosuppression with the lowest possible toxicity. Components of immunosuppression include induction and maintenance regimens. Primary graft failure remains an important cause of mortality and morbidity in the immediate post-transplant period. Acute rejection is a common complication after lung transplant, but responds well to augmented immunosuppression and immunomodulation. Chronic rejection still is the major cause of mortality in patients who survive the initial year post-transplantation. Several new drugs have shown promise in decreasing the rate of loss of graft function. This review discusses the current and emerging therapeutic regimens.