Sequential analysis of myofibroblast differentiation and transforming growth factor-β1/Smad pathway activation in murine pulmonary fibrosis

Redox mechanisms in autoimmune thyroid eye disease

Thyroid eye disease (TED) is an autoimmune condition affecting the orbit and the eye with its adnexa, often occurring as an extrathyroidal complication of Graves' disease (GD). Orbital inflammatory infiltration and the stimulation of orbital fibroblasts, triggering de novo adipogenesis, an overproduction of hyaluronan, myofibroblast differentiation, and eventual tissue fibrosis are hallmarks of the disease. Notably, several redox signaling pathways have been shown to intensify inflammation and to promote adipogenesis, myofibroblast differentiation, and fibrogenesis by upregulating potent cytokines, such as interleukin (IL)-1β, IL-6, and transforming growth factor (TGF)-β. While existing treatment options can manage symptoms and potentially halt disease progression, they come with drawbacks such as relapses, side effects, and chronic adverse effects on the optic nerve. Currently, several studies shed light on the pathogenetic contributions of emerging factors within immunological cascades and chronic oxidative stress. This review article provides an overview on the latest advancements in understanding the pathophysiology of TED, with a special focus of the interplay between oxidative stress, immunological mechanisms and environmental factors. Furthermore, cutting-edge therapeutic approaches targeting redox mechanisms will be presented and discussed.

An Exosome-Rich Conditioned Medium from Human Amniotic Membrane Stem Cells Facilitates Wound Healing via Increased Reepithelization, Collagen Synthesis, and Angiogenesis

Tissue regeneration is an essential requirement for wound healing and recovery of organs' function. It has been demonstrated that wound healing can be facilitated by activating paracrine signaling mediated by exosomes secreted from stem cells, since exosomes deliver many functional molecules including growth factors (GFs) and neurotrophic factors (NFs) effective for tissue regeneration. In this study, an exosome-rich conditioned medium (ERCM) was collected from human amniotic membrane stem cells (AMSCs) by cultivating the cells under a low oxygen tension (2% O2 and 5% CO2). The contents of GFs and NFs including keratinocyte growth factor, epidermal growth factor, fibroblast growth factor 1, transforming growth factor-β, and vascular endothelial growth factor responsible for skin regeneration were much higher (10-30 folds) in the ERCM than in normal conditioned medium (NCM). In was found that CM-DiI-labeled exosomes readily entered keratinocytes and fibroblasts, and that ERCM not only facilitated the proliferation of keratinocytes in normal condition, but also protected against H2O2 cytotoxicity. In cell-migration assay, the scratch wound in keratinocyte culture dish was rapidly closed by treatment with ERCM. Such wound-healing effects of ERCM were confirmed in a rat whole skin-excision model: i.e., the wound closure was significantly accelerated, remaining minimal crusts, by topical application of ERCM solution (4 × 109 exosome particles/100 μL) at 4-day intervals. In the wounded skin, the deposition of collagens was enhanced by treatment with ERCM, which was supported by the increased production of collagen-1 and collagen-3. In addition, enhanced angiogenesis in ERCM-treated wounds was confirmed by increased von Willebrand factor (vWF)-positive endothelial cells. The results indicate that ERCM from AMSCs with high concentrations of GFs and NFs improves wound healing through tissue regeneration not only by facilitating keratinocyte proliferation for skin repair, but also activating fibroblasts for extracellular matrix production, in addition to the regulation of angiogenesis and scar tissue formation.

Inhibition of p38 mitogen-activated protein kinases may attenuate scar proliferation after cleft lip surgery in rabbits via Smads signaling pathway

Background

Cleft lip repair surgery always results in visible scarring. It has been proved that scar formation can be reduced by inhibiting the p38 mitogen-activated protein kinases (p38MAPKs) signaling pathway. However, the interaction between p38MAPK and Smads in scar formation is still controversial.

Methods

This study was designed to investigate whether inhibition of p38MAPK reduces postoperative scar formation of cleft lips on rabbits via the Smads signaling pathway. Scar models in rabbits after cleft lip surgery were created and their fibroblasts were extracted. Then the expression of p38MAPK was disturbed by adenovirus in vitro and Vivo. The scar thickness was measured and scar tissues were excised for Sirius red staining and immunohistochemistry to detect the expression of type I collagen (col I), type III collagen (col III), and α-smooth muscle actin (α-SMA). The underlying mechanisms of p38MAPK knockdown on the extracellular matrix and Smad signaling pathway were invested in vitro using the EdU assay, Western blot, RT PCR, and immunofluorescence.

Results

p38MAPK knockdown suppresses the expression of p-smad3 and p-smad2 in fibroblasts, modulating the expression of its target genes, such as α-SMA, col I, and col III. When Ad-P38MAPK-1 was injected into lip scar, it reduced the expression of scar-related genes and scar thickness when compared to the negative control groups.

Conclusions

In rabbits, inhibiting p38MAPK expression prevents scar proliferation through inhibiting the Smad signaling pathway after cleft lip surgery.

Protective effect of ebselen on bleomycin-induced lung fibrosis: analysis of the molecular mechanism of lung fibrosis mediated by oxidized diacylglycerol

The molecular mechanisms underlying the development of pulmonary fibrosis remain unknown, and effective treatments have not yet been developed. It has been shown that oxidative stress is involved in lung fibrosis. Oxidized diacylglycerol (DAG) produced by oxidative stress is thought to play an important role in lung fibrosis. This study assessed the effect of oxidized DAG in an animal model of pulmonary fibrosis induced by aspiration of bleomycin (BLM) into the lungs. The inhibitory effect of ebselen on pulmonary fibrosis was also investigated. In lung fibrotic tissue induced by BLM, an increase in lipid peroxides and collagen accumulation was observed. Moreover, the levels of oxidized DAG, which has strong protein kinase C (PKC) activation activity, were significantly increased over time following the administration of BLM. Western blotting showed that phosphorylation of PKCα and δ isoforms was increased by BLM. Oral administration of ebselen significantly suppressed the increase in oxidized DAG induced by BLM and improved lung fibrosis. PKCα and δ phosphorylation were also significantly inhibited. The mRNA expression of α-smooth muscle actin and collagen I (marker molecules for fibrosis), as well as the production of transforming growth factor-β and tumor necrosis factor-α(a potentially important factor in the fibrotic process), were increased by BLM and significantly decreased by ebselen. The administration of BLM may induce lipid peroxidation in lung tissue, while the oxidized DAG produced by BLM may induce overactivation of PKCα and δ, resulting in the induction of lung fibrosis.

Thinking inside the box: Current insights into targeting orbital tissue remodeling and inflammation in thyroid eye disease

Thyroid eye disease (TED) is an autoimmune disorder that manifests in the orbit. In TED, the connective tissue behind the eye becomes inflamed and remodels with increased fat accumulation and/or increased muscle and scar tissue. As orbital tissue expands, patients develop edema, exophthalmos, diplopia, and optic neuropathy. In severe cases vision loss may occur secondary to corneal scarring from exposure or optic nerve compression. Currently there is no cure for TED, and treatments are limited. A major breakthrough in TED therapy occurred with the FDA approval of teprotumumab, a monoclonal insulin-like growth factor 1 receptor (IGF1R) blocking antibody. Yet, teprotumumab therapy has limitations, including cost, infusion method of drug delivery, variable response, and relapse. We describe approaches to target orbital fibroblasts and the complex pathophysiology that underlies tissue remodeling and inflammation driving TED. Further advances in the elucidation of the mechanisms of TED may lead to prophylaxis based upon early biomarkers as well as lead to more convenient, less expensive therapies.

Study of Interleukin-1Beta Expression in Acne Vulgaris and Acne Scars

BACKGROUND

Acne vulgaris is a multifactorial disease that mostly heals by scarring. Interleukin-1 beta (IL-1β) is a proinflammatory cytokine, suggested to play a key role in acne pathogenesis.

OBJECTIVE

To study the immunohistochemical (IHC) expression of IL1β in acne vulgaris and acne scars to evaluate its possible role in their pathogenesis and to study the relation between expression of IL1β and the clinicopathological parameters.

PATIENTS AND METHODS

This study was conducted on sixty subjects (twenty patients with acne vulgaris and twenty patients with acne scars), and twenty healthy volunteers as controls. Skin biopsies were taken from patients and controls for routine histopathological examination with Hematoxylin and Eosin (H&E) stain and IHC staining of IL-1β.

RESULTS

There was a statistically significant increase in expression of IL-1β in acne vulgaris compared to post-acne scars and controls, (p<0.001) for both. IL-1β expression was significantly positively correlated with both clinical severity of acne vulgaris (p=0.022) and severity of histopathological inflammation (p=0.011).

CONCLUSION

IL-1β expression was associated with acne vulgaris and post acne scars with significant positive correlation to clinical and histopathological severity of acne vulgaris. Thus IL-1β could be a key player cytokine in acne pathogenesis, its severity and development of post acne scars.

RhoGTPase in Vascular Disease

Ras-homologous (Rho)A/Rho-kinase pathway plays an essential role in many cellular functions, including contraction, motility, proliferation, and apoptosis, inflammation, and its excessive activity induces oxidative stress and promotes the development of cardiovascular diseases. Given its role in many physiological and pathological functions, targeting can result in adverse effects and limit its use for therapy. In this review, we have summarized the role of RhoGTPases with an emphasis on RhoA in vascular disease and its impact on endothelial, smooth muscle, and heart and lung fibroblasts. It is clear from the various studies that understanding the regulation of RhoGTPases and their regulators in physiology and pathological conditions is required for effective targeting of Rho.

Downregulation of microRNA‑30a in bronchoalveolar lavage fluid from idiopathic pulmonary fibrosis patients

MicroRNAs (miRs) are short, highly conserved small noncoding RNA molecules with fundamental roles in regulating gene expression. To identify miR biomarkers associated with idiopathic pulmonary fibrosis (IPF), the expression pattern of miRs in exosomes from bronchoalveolar lavage fluid (BALF) of elderly patients with IPF were evaluated. High‑throughput quantitative detection of miR expression using a microarray indicated that miR‑125b, miR‑128, miR‑21, miR‑100, miR‑140‑3p and miR‑374b were upregulated in patients with IPF, while let‑7d, miR‑103, miR‑26 and miR‑30a‑5p were downregulated. The expression level of miR‑30a‑5p was further examined, and its potential target genes were predicted using target gene prediction analysis software. A direct regulatory association was confirmed between miR‑30a‑5p and TGF‑β activated kinase 1/MAP3K7 binding protein 3 (TAB3) via a dual‑luciferase reporter assay. Overexpression of miR‑30a‑5p decreased TAB3, α‑smooth muscle actin and fibronectin expression in A549 cells with or without transforming growth factor‑β1 treatment. The decreased expression of miR‑30a in the BALF of patients with IPF, along with the consequential increase in TAB3 expression, may be a crucial factor in IPF progression.

Mechanisms of pulmonary fibrosis induced by core fucosylation in pericytes

Pulmonary fibrosis is a common outcome of a variety of pulmonary interstitial diseases, and myofibroblasts are the main culprit for this process. Recent studies have found that pericytes are one of the major sources of myofibroblasts; the transformation of which involves a complex process of activation of TGF-β/Smad2/3 and PDGFβ/Erk signaling pathways. We have reported that the transforming growth factor-β receptor and platelet-derived growth factor-β receptor (TGF-βR I and PDGFβR, respectively) are modified by glycosylation. Thus, we hope to regulate the above-mentioned signal pathways through core fucosylation (CF) catalyzed by α-1,6-fucosyltransferase (FUT8). Previous work has confirmed that TGF-β1 can induce the transformation of pericytes into myofibroblasts, while FUT8siRNA can inhibit such transformation. In the present study, we used an adenovirus packaging FUT8 shRNA to infect a bleomycin-induced pulmonary fibrosis mouse model and determined the effect of CF on pulmonary fibrosis by analyzing the mechanism of CF-mediated pericyte transformation. Our findings may shed new light on the mechanism of pulmonary interstitial fibrosis and provide a novel therapeutic target for clinical applications.

Quercetin Inhibits Pulmonary Arterial Endothelial Cell Transdifferentiation Possibly by Akt and Erk1/2 Pathways

This study aimed to investigate the effects and mechanisms of quercetin on pulmonary arterial endothelial cell (PAEC) transdifferentiation into smooth muscle-like cells. TGF-β1-induced PAEC transdifferentiation models were applied to evaluate the pharmacological actions of quercetin. PAEC proliferation was detected with CCK8 method and BurdU immunocytochemistry. Meanwhile, the identification and transdifferentiation of PAECs were determined by FVIII immunofluorescence staining and α-SMA protein expression. The related mechanism was elucidated based on the levels of Akt and Erk1/2 signal pathways. As a result, quercetin effectively inhibited the TGF-β1-induced proliferation and transdifferentiation of the PAECs and activation of Akt/Erk1/2 cascade in the cells. In conclusion, quercetin is demonstrated to be effective for pulmonary arterial hypertension (PAH) probably by inhibiting endothelial transdifferentiation possibly via modulating Akt and Erk1/2 expressions.

Suppressive effect of microRNA-29b on hepatic stellate cell activation and its crosstalk with TGF-β1/Smad3

The microRNA (miR)‐29 family is closely associated with fibrotic processes by virtue of its low expression in many tissues during organ fibrosis. The present study investigated whether miR‐29b overexpression suppressed hepatic stellate cell (HSC) activation and its interactions with transforming growth factor (TGF)‐β1/mothers against decapentaplegic homolog 3 (Smad3), a classical signal transduction pathway contributing to the activation of HSCs. The results showed that transfection of LX‐2 (human HSC) cells with miR‐29b mimic or pSUPER‐Smad3 silencing (si)RNA resulted in significantly increased expression of miR‐29b and decreased expression of Smad3. miR‐29b overexpression inhibited proliferation of LX‐2 cells 24 h after transfection. Both miR‐29b overexpression and Smad3 silencing antagonized the effects of TGF‐β1 on the expression of α‐smooth muscle actin (α‐SMA) and collagen type I (col‐1). Furthermore, infection with miR‐29b mimics suppressed Smad3 and TGF‐β1 expression, suggesting that miR‐29b inhibited LX‐2 activation mediated by both Smad3 and TGF‐β1. Nevertheless, primary miR‐29a/b1, miR‐29b2/c and mature miR‐29b were downregulated by TGF‐β1 and stimulated by Smad3 silencing, suggesting that TGF‐β1/Smad3 signalling pathway regulate not just mature miR‐29b but also its transcription. In summary, our results show overwhelming evidence corroborating the suppressive effect of miR‐29b on TGF‐β1‐induced LX‐2 cell activation. The results also revealed the existence of crosstalk between miR‐29b and TGF‐β1/Smad3 during LX‐2 activation, suggesting a feedback loop between miR‐29b and TGF‐β1/Smad3 signalling that promotes liver fibrosis. Copyright © 2016 The Authors. Cell Biochemistry and Function published by John Wiley & Sons, Ltd.

Salinomycin and other polyether ionophores are a new class of antiscarring agent

Although scarring is a component of wound healing, excessive scar formation is a debilitating condition that results in pain, loss of tissue function, and even death. Many tissues, including the lungs, heart, skin, and eyes, can develop excessive scar tissue as a result of tissue injury, chronic inflammation, or autoimmune disease. Unfortunately, there are few, if any, effective treatments to prevent excess scarring, and new treatment strategies are needed. Using HEK293FT cells stably transfected with a TGFβ-dependent luciferase reporter, we performed a small molecule screen to identify novel compounds with antiscarring activity. We discovered that the polyether ionophore salinomycin potently inhibited the formation of scar-forming myofibroblasts. Salinomycin (250 nm) blocked TGFβ-dependent expression of the cardinal myofibroblast products α smooth muscle actin, calponin, and collagen in primary human fibroblasts without causing cell death. Salinomycin blocked phosphorylation and activation of TAK1 and p38, two proteins fundamentally involved in signaling myofibroblast and scar formation. Expression of constitutively active mitogen activated kinase kinase 6, which activates p38 MAPK, attenuated the ability of salinomycin to block myofibroblast formation, demonstrating that salinomycin targets the p38 kinase pathway to disrupt TGFβ signaling. These data identify salinomycin and other polyether ionophores as novel potential antiscarring therapeutics.

Role of Klotho, an antiaging protein, in pulmonary fibrosis

Klotho is a recently discovered antiaging protein. Although many researchers are investigating the roles of Klotho in chronic kidney diseases and cancer, however, there are no studies on the roles of Klotho in chronic pulmonary diseases. The purpose of this study was to define the role of Klotho in pulmonary fibrosis using a murine model of ovalbumin (OVA)-induced chronic asthma and in BEAS-2B human bronchial epithelial cells. In an in vivo experiment, mice were sensitized by intraperitoneal injection of OVA (20 μg/mouse), followed 1 week later by an airway challenge with 1 % OVA solution delivered three times a week for 4 weeks. In an in vitro experiment, we investigated the effects of stimulated with interleukin (IL)-4 and tumor necrosis factor (TNF)-α on Klotho protein and VEGF and transforming growth factor (TGF)-β1/Smad3 signaling in BEAS-2B cells. Klotho decreased and VEGF and TGF-β1 levels increased with increasing duration of OVA challenge. Similar findings were found for the expression of these proteins in lung tissue. The collagen content in lung tissue increased with repeated OVA challenge. In the in vitro experiment, Klotho expression decreased and VEGF and TGF-β1/Smad3 expression increased after IL-4 (50 ng/mL) and TNF-α (50 ng/mL) stimulation. Pretreatment with 25, 50, and 100 ng/mL of Klotho protein significantly attenuated the increases in VEGF and TGF-β1/Smad3 expression levels after IL-4 and TNF-α treatment, and reduced α-smooth muscle actin expression in concentration-dependent manner. Klotho protein inhibited the fibrotic response by suppressing VEGF and TGF-β1/Smad3 expression. These results suggest that Klotho protein may be crucial to inhibiting fibrosis associated with chronic airway diseases.

Interleukin-1β attenuates myofibroblast formation and extracellular matrix production in dermal and lung fibroblasts exposed to transforming growth factor-β1

One of the most potent pro-fibrotic cytokines is transforming growth factor (TGFβ). TGFβ is involved in the activation of fibroblasts into myofibroblasts, resulting in the hallmark of fibrosis: the pathological accumulation of collagen. Interleukin-1β (IL1β) can influence the severity of fibrosis, however much less is known about the direct effects on fibroblasts. Using lung and dermal fibroblasts, we have investigated the effects of IL1β, TGFβ1, and IL1β in combination with TGFβ1 on myofibroblast formation, collagen synthesis and collagen modification (including prolyl hydroxylase, lysyl hydroxylase and lysyl oxidase), and matrix metalloproteinases (MMPs). We found that IL1β alone has no obvious pro-fibrotic effect on fibroblasts. However, IL1β is able to inhibit the TGFβ1-induced myofibroblast formation as well as collagen synthesis. Glioma-associated oncogene homolog 1 (GLI1), the Hedgehog transcription factor that is involved in the transformation of fibroblasts into myofibroblasts is upregulated by TGFβ1. The addition of IL1β reduced the expression of GLI1 and thereby also indirectly inhibits myofibroblast formation. Other potentially anti-fibrotic effects of IL1β that were observed are the increased levels of MMP1, −2, −9 and −14 produced by fibroblasts exposed to TGFβ1/IL1β in comparison with fibroblasts exposed to TGFβ1 alone. In addition, IL1β decreased the TGFβ1-induced upregulation of lysyl oxidase, an enzyme involved in collagen cross-linking. Furthermore, we found that lung and dermal fibroblasts do not always behave identically towards IL1β. Suppression of COL1A1 by IL1β in the presence of TGFβ1 is more pronounced in lung fibroblasts compared to dermal fibroblasts, whereas a higher upregulation of MMP1 is seen in dermal fibroblasts. The role of IL1β in fibrosis should be reconsidered, and the differences in phenotypical properties of fibroblasts derived from different organs should be taken into account in future anti-fibrotic treatment regimes.

Interleukin-1β attenuates myofibroblast formation and extracellular matrix production in dermal and lung fibroblasts exposed to transforming growth factor-β1

One of the most potent pro-fibrotic cytokines is transforming growth factor (TGFβ). TGFβ is involved in the activation of fibroblasts into myofibroblasts, resulting in the hallmark of fibrosis: the pathological accumulation of collagen. Interleukin-1β (IL1β) can influence the severity of fibrosis, however much less is known about the direct effects on fibroblasts. Using lung and dermal fibroblasts, we have investigated the effects of IL1β, TGFβ1, and IL1β in combination with TGFβ1 on myofibroblast formation, collagen synthesis and collagen modification (including prolyl hydroxylase, lysyl hydroxylase and lysyl oxidase), and matrix metalloproteinases (MMPs). We found that IL1β alone has no obvious pro-fibrotic effect on fibroblasts. However, IL1β is able to inhibit the TGFβ1-induced myofibroblast formation as well as collagen synthesis. Glioma-associated oncogene homolog 1 (GLI1), the Hedgehog transcription factor that is involved in the transformation of fibroblasts into myofibroblasts is upregulated by TGFβ1. The addition of IL1β reduced the expression of GLI1 and thereby also indirectly inhibits myofibroblast formation. Other potentially anti-fibrotic effects of IL1β that were observed are the increased levels of MMP1, -2, -9 and -14 produced by fibroblasts exposed to TGFβ1/IL1β in comparison with fibroblasts exposed to TGFβ1 alone. In addition, IL1β decreased the TGFβ1-induced upregulation of lysyl oxidase, an enzyme involved in collagen cross-linking. Furthermore, we found that lung and dermal fibroblasts do not always behave identically towards IL1β. Suppression of COL1A1 by IL1β in the presence of TGFβ1 is more pronounced in lung fibroblasts compared to dermal fibroblasts, whereas a higher upregulation of MMP1 is seen in dermal fibroblasts. The role of IL1β in fibrosis should be reconsidered, and the differences in phenotypical properties of fibroblasts derived from different organs should be taken into account in future anti-fibrotic treatment regimes.

The effect of NF-κB antisense oligonucleotide on transdifferentiation of fibroblast in lung tissue of mice injured by bleomycin

To investigate the influence of NF-κB antisense oligonucleotide on transdifferentiation of fibroblast in the pathological process of bleomycin-induced pulmonary fibrosis in mice. 6 h before molding of C57BL/6 model of pulmonary fibrosis in mice, NF-κB antisense oligonucleotide was injected from caudal vein. Then the lung tissue was collected for primary culture as well as model group and control group. Cultured cells were used for immunocytochemical staining of p65, IκB-α and α-SMA proteins as well as in situ hybridization staining of p65 and IκB-α. Then image analysis was carried out. The expressions of all the indicators were expressed as mean optical density. Compared with the control group, the expressions of p65 protein, IκB-α protein and α-SMA protein of model group were increased, as well as the expressions of p65 mRNA and IκB-α mRNA (P < 0.05). Compared with model group, the expressions of all indicators of intervention group were decreased (P < 0.05). P65 protein and p65 mRNA were positively correlated with the expression of α-SMA protein respectively. p65 protein and p65 mRNA were positively correlated with the expressions of IκB-α protein and IκB-α mRNA respectively. NF-κB antisense oligonucleotide can inhibit the transdifferentiation of fibroblast towards myofibroblast in the pathological process of bleomycin-induced pulmonary fibrosis in mice.

A new antifibrotic target of Ac-SDKP: inhibition of myofibroblast differentiation in rat lung with silicosis

Background

Myofibroblast differentiation, characterized by α-smooth muscle actin (α-SMA) expression, is a key process in organ fibrosis, and is induced by TGF-β. Here we examined whether an anti-fibrotic agent, N-acetyl-seryl-aspartyl-lysylproline (Ac-SDKP), can regulate induction of TGF-β signaling and myofibroblast differentiation as a potential key component of its anti-fibrotic mechanism in vivo and in vitro.

Methodology/Principal Findings

Rat pulmonary fibroblasts were cultured in vitro and divided to 4 groups 1) control; 2) TGF-β1; 3) TGF-β1+ LY364947; 4) TGF-β1+Ac-SDKP. For in vivo studies, six groups of animals were utilized 1) control 4w; 2) silicotic 4w; 3) control 8w; 4) silicotic 8w; 5) Ac-SDKP post-treatment; 6)Ac-SDKP pre-treatment. SiO₂ powders were douched in the trachea of rat to make the silicotic model. Myofibroblast differentiation was measured by examining expression of α-SMA, as well as expression of serum response factor (SRF), a key regulator of myofibroblast differentiation. The expressions of collagen, TGF-β1 and RAS signaling were also assessed. The results revealed that TGF-β1 strongly induced myofibroblast differentiation and collagen synthesis in vitro, and that pre-treatment with Ac-SDKP markedly attenuated myofibroblast activation, as well as induction of TGF-β1 and its receptor. Similar results were observed in vivo in the pathologically relevant rat model of silicosis. Ac-SDKP treatment in vivo strongly attenuated 1) silicosis-induced increased expressions of TGF-β1 and RAS signaling, 2) myofibroblast differentiation as indicated by a robust decrease of SRF and α-SMA-positive myofibroblast localization in siliconic nodules in the lung, 3) collagen deposition.

Conclusion/Significance

The results of the present study suggest a novel mechanism of action for Ac-SDKP’s beneficial effect in silicosis, which involves attenuation of TGF-β1 and its receptors, SRF and Ang II type 1 receptor (AT₁) expression, collagen deposition and myofibroblast differentiation. The results further suggest that therapies targeting myofibroblast differentiation may have therapeutic efficacy in treatment of silicosis of the lung.