Protective effects of GHK-Cu in bleomycin-induced pulmonary fibrosis via anti-oxidative stress and anti-inflammation pathways

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a serious lung problem with advancing and diffusive pulmonary fibrosis as the pathologic basis, and with oxidative stress and inflammation as the key pathogenesis. Glycyl-L-histidyl-l-lysine (GHK) is a tripeptide participating into wound healing and regeneration. GHK-Cu complexes improve GHK bioavailability. Thus, the current study aimed to explore the therapeutic role of GHK-Cu on bleomycin (BLM)-induced pulmonary fibrosis in a mouse model.

METHODS

BLM (3 mg/kg) was administered via tracheal instillation (TI) to induce a pulmonary fibrosis model in C57BL/6j mice 21 days after the challenge of BLM. GHK-Cu was injected intraperitoneally (i.p.) at different dosage of 0.2, 2 and 20 μg/g/day in 0.5 ml PBS on alternate day. The histological changes, inflammation response, the collagen deposition and epithelial-mesenchymal transition (EMT) was evaluated in the lung tissue. EMT was evaluated by ɑ-SMA and fibronectin expression in the lung tissue. NF-κB p65, Nrf2 and TGFβ1/Smad2/3 signalling pathways were detected by immunoblotting analysis.

RESULTS

GHK-Cu complex inhibited BLM-induced inflammatory and fibrotic pathological changes, alleviated the inflammatory response in the BALF by reducing the levels of the inflammatory cytokines, TNF-ɑ and IL-6 and the activity of MPO as well as reduced collagen deposition. In addition, the GHK-Cu treatment significantly reversed the MMP-9/TIMP-1 imbalance and partially prevented EMT via Nrf2, NF-κB and TGFβ1 pathways, as well as Smad2/3 phosphorylation.

CONCLUSIONS

GHK-Cu presented a protective effect in BLM-induced inflammation and oxidative stress by inhibiting EMT progression and suppressing TGFβ1/Smad2/3 signalling in pulmonary fibrosis.

Nrf2-dependent induction of innate host defense via heme oxygenase-1 inhibits Zika virus replication

We identified primary human monocyte-derived macrophages (MDM) as vulnerable target cells for Zika virus (ZIKV) infection. We demonstrate dramatic effects of hemin, the natural inducer of the heme catabolic enzyme heme oxygenase-1 (HO-1), in the reduction of ZIKV replication in vitro. Both LLC-MK2 monkey kidney cells and primary MDM exhibited hemin-induced HO-1 expression with major reductions of >90% in ZIKV replication, with little toxicity to infected cells. Silencing expression of HO-1 or its upstream regulatory gene, nuclear factor erythroid-related factor 2 (Nrf2), attenuated hemin-induced suppression of ZIKV infection, suggesting an important role for induction of these intracellular mediators in retarding ZIKV replication. The inverse correlation between hemin-induced HO-1 levels and ZIKV replication provides a potentially useful therapeutic modality based on stimulation of an innate cellular response against Zika virus infection.

Propofol Attenuates Early Brain Injury After Subarachnoid Hemorrhage in Rats

Our previous studies demonstrated that propofol protects rat brain against focal cerebral ischemia. However, whether propofol attenuates early brain injury after subarachnoid hemorrhage in rats remains unknown until now. The present study was performed to evaluate the effect of propofol on early brain injury after subarachnoid hemorrhage in rats and further explore the potential mechanisms. Sprague-Dawley rats underwent subarachnoid hemorrhage (SAH) by endovascular perforation then received treatment with propofol (10 or 50 mg/kg) or vehicle after 2 and 12 h of SAH. SAH grading, neurological scores, brain water content, Evans blue extravasation, the myeloperoxidase activity, and malondialdehyde (MDA) content were measured 24 h after SAH. Expression of nuclear factor erythroid-related factor 2 (Nrf2), nuclear factor-kappa B (NF-κB) p65, and aquaporin 4 (AQP4) expression in rat brain were detected by Western blot. Expression of cyclooxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) were determined by reverse transcription-polymerase chain reaction (RT-PCR). Expressions of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were assessed by ELISA. Neurological scores, brain water content, Evans blue extravasation, the myeloperoxidase activity, and MDA content were significantly reduced by propofol. Furthermore, expression of Nrf2 in rat brain was upregulated by propofol, and expression of NF-κB p65, AQP4, COX-2, MMP-9, TNF-α, and IL-1β in rat brain were attenuated by propofol. Our results demonstrated that propofol improves neurological scores, reduces brain edema, blood-brain barrier (BBB) permeability, inflammatory reaction, and lipid peroxidation in rats of SAH. Propofol exerts neuroprotection against SAH-induced early brain injury, which might be associated with the inhibition of inflammation and lipid peroxidation.

The thioredoxin antioxidant system

The thioredoxin (Trx) system, which is composed of NADPH, thioredoxin reductase (TrxR), and thioredoxin, is a key antioxidant system in defense against oxidative stress through its disulfide reductase activity regulating protein dithiol/disulfide balance. The Trx system provides the electrons to thiol-dependent peroxidases (peroxiredoxins) to remove reactive oxygen and nitrogen species with a fast reaction rate. Trx antioxidant functions are also shown by involvement in DNA and protein repair by reducing ribonucleotide reductase, methionine sulfoxide reductases, and regulating the activity of many redox-sensitive transcription factors. Moreover, Trx systems play critical roles in the immune response, virus infection, and cell death via interaction with thioredoxin-interacting protein. In mammalian cells, the cytosolic and mitochondrial Trx systems, in which TrxRs are high molecular weight selenoenzymes, together with the glutathione-glutaredoxin (Grx) system (NADPH, glutathione reductase, GSH, and Grx) control the cellular redox environment. Recently mammalian thioredoxin and glutathione systems have been found to be able to provide the electrons crossly and to serve as a backup system for each other. In contrast, bacteria TrxRs are low molecular weight enzymes with a structure and reaction mechanism distinct from mammalian TrxR. Many bacterial species possess specific thiol-dependent antioxidant systems, and the significance of the Trx system in the defense against oxidative stress is different. Particularly, the absence of a GSH-Grx system in some pathogenic bacteria such as Helicobacter pylori, Mycobacterium tuberculosis, and Staphylococcus aureus makes the bacterial Trx system essential for survival under oxidative stress. This provides an opportunity to kill these bacteria by targeting the TrxR-Trx system.