Interaction of N-acetyl-seryl-aspartyl-lysyl-proline with the angiotensin-converting enzyme 2-angiotensin-(1-7)-Mas axis attenuates pulmonary fibrosis in silicotic rats.

What is the central question of this study? What are the effects of the antifibrotic peptide acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) on the angiotensin-converting enzyme 2 (ACE2)-angiotensin-(1-7)-Mas axis during the occurrence and progression of silicosis? What is the main finding and its importance? Ac-SDKP inhibited lung fibrosis in rats exposed to silica by activation of the ACE2-angiotensin-(1-7)-Mas axis. Angiotensin-(1-7) potentially promotes Ac-SDKP by increasing the level of meprin α, the major synthetase of Ac-SDKP. Thus, the interaction Ac-SDKP and angiotesin-(1-7) in silicosis could provide a new therapeutic strategy. The central role of angiotensin-converting enzyme (ACE) in the occurrence and progression of silicosis has been established. The antifibrotic peptide acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) can be degraded by ACE. The ACE2-angiotensin-(1-7)-Mas axis is protective and acts to counterbalance the detrimental effects of ACE-angiotensin II (Ang II)-Ang II type 1 receptor and exerts antifibrotic effects. Here, we demonstrate an interaction between Ac-SDKP and Ang-(1-7) in the inhibition of collagen deposition and myofibroblast differentiation in rats exposed to silica. Treatment with Ac-SDKP increased the level of ACE2-Ang-(1-7)-Mas in rats or in cultured fibroblasts and decreased the levels of collagen type I and α-smooth muscle actin. Furthermore, exogenous Ang-(1-7) had similar antifibrotic effects and increased the level of meprin α, a major Ac-SDKP synthetase, both in vivo and in vitro. Compared with non-silicotic patients exposed to silica, the level of serum ACE was increased in patients with silicosis phase III; the levels of Ang II and Ang-(1-7) were high in patients with silicosis phase II; and the level of Ac-SDKP was high in the silicosis phase III group. These data imply that Ac-SDKP and Ang-(1-7) have an interactive effect as regulatory peptides of the renin-angiotensin system and exert antifibrotic effects.

Gao X ，Xu H ，Zhang B ，Tao T ，Liu Y ，Xu D ，Cai W ，Wei Z ，Li S ，Zhang H ，Mao N ，Zhang G ，Li D ，Jin F ，Li S ，Zhang L ，Liu H ，Hao X ，Yang F ... -  《-》

N-Acetyl-Seryl-Asparyl-Lysyl-Proline regulates lung renin angiotensin system to inhibit epithelial-mesenchymal transition in silicotic mice.

Silicosis is a major public health concern with various contributing factors. The renin-angiotensin system (RAS)is a critical regulator in the pathogenesis of this disease. We focused on two key RAS enzymes, angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2), to elucidate the activation of the ACE-angiotensin II (Ang II)-angiotensin II receptor 1 (AT1) axis and the inhibition of the ACE2-angiotensin-(1-7) [Ang-(1-7)]-Mas receptor axis in C57BL/6mice following SiO2 treatment. Silica exposure caused nodule formation, pulmonary interstitial fibrosis, epithelial-mesenchymal transition (EMT), abnormal deposition of extracellular matrix, and impaired lung function in mice. These effects were attenuated by the inhibition of ACE (captopril), blockade of the AT1(losartan), or systemic knockdown of the Ace gene. These effects were exacerbated by the inhibition of ACE2 (MLN-4760), blockade of the Mas (A779), or knockdown of the Ace2 gene. N-Acetyl-Seryl-Asparyl-Lysyl-Proline (Ac-SDKP), an anti-fibrotic peptide, ameliorated the silica-exposure-induced pathological changes by targeting the RAS system by activating the protective ACE2-Ang-(1-7)-Mas axis and inhibiting the deleterious ACE-Ang II-AT1 axis, thereby exerting a protective effect. This was confirmed in mouse lung type II epithelial cells (MLE-12) pretreated with Ang II and/or gene silencing separately targeting Ace and Ace2.The effects of Ac-SDKP were similar to those produced by Ace gene silencing and were partly attenuated by Ace2 deficiency. These findings suggested that RAS plays critical roles in the pathomechanism of silicosis fibrosis and that Ac-SDKP regulates lung RAS to inhibit EMT in silicotic mice and MLE-12 cells.

Li S ，Li Y ，Zhang Y ，Li S ，Zhang M ，Jin F ，Wei Z ，Yang Y ，Gao X ，Mao N ，Ge X ，Xu H ，Yang F ... -  《-》

[Inhibition effect of N-acetyl-seryl-aspartyl-lysyl-proline on myofibroblast differentiation by regulating acetylated tubulin α in silicotic rat model].

Li S ，Gao X ，Xu D ，Wang X ，Liu Y ，Zhang L ，Deng H ，Wei Z ，Tian J ，Xu H ，Yang F ... -  《-》

Targeting the RAS axis alleviates silicotic fibrosis and Ang II-induced myofibroblast differentiation via inhibition of the hedgehog signaling pathway.

The hedgehog (HH) signaling pathway plays an important role in lung development, but its significance in silicosis is unclear. We showed that in human coal pneumoconiosis autopsy specimens, Sonic Hedgehog (SHH) and the Glioma-associated oncogene homolog transcription factors family (GLI) 1 proteins were up-regulated, whereas Patch-1 (PTC) was down-regulated. The protein levels of SHH, smoothened (SMO), GLI1, GLI2, α-smooth muscle actin (α-SMA) and collagen type Ⅰ (Col Ⅰ) were also elevated gradually in the bronchoalveolar lavage fluid (BALF) of different stages of coal pneumoconiosis patients, dynamic silica-inhalation rat lung tissue and MRC-5 cells induced by Ang II at different time points, whereas the PTC and GLI3 levels were diminished gradually. Ac-SDKP, an active peptide of renin-angiotensin system (RAS), is an anti-fibrotic tetrapeptide. Targeting RAS axis also has anti-silicotic fibrosis effects. However, their roles on the HH pathway are still unknown. Here, we reported that Ac-SDKP + Captopril, Ac-SDKP, Captopril, or Ang (1-7) could alleviate silicotic fibrosis and collagen deposition, as well as improve the lung functions of silicotic rat. These treatments decreased the expression of SHH, SMO, GLI1, GLI2, α-SMA, and Col Ⅰ and increased the expression of PTC and GLI3 on both the silicotic rat lung tissue and MRC-5 cells induced by Ang II. We also reported that Ang II may promote myofibroblast differentiation via the GLI1 transcription factor and independently of the SMO receptor.

Zhang B ，Xu H ，Zhang Y ，Yi X ，Zhang G ，Zhang X ，Xu D ，Gao X ，Li S ，Zhu Y ，Zhang H ，Wei Z ，Li S ，Zhang L ，Wang R ，Yang F ... -  《-》

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

Xu H ，Yang F ，Sun Y ，Yuan Y ，Cheng H ，Wei Z ，Li S ，Cheng T ，Brann D ，Wang R ... -  《PLoS One》