Fraxinol attenuates LPS-induced acute lung injury by equilibrating ACE-Ang II-AT1R and ACE2-Ang (1-7)-Mas and inhibiting NLRP3

Potential pharmaceuticals targeting neuroimmune interactions in treating acute lung injury

BACKGROUND AND MAIN BODY

Although interactions between the nervous and immune systems have been recognized decades ago, it has become increasingly appreciated that neuroimmune crosstalk is among the driving factors of multiple pulmonary inflammatory diseases including acute lung injury (ALI). Here, we review the current understanding of nerve innervations towards the lung and summarize how the neural regulation of immunity and inflammation participates in the onset and progression of several lung diseases, especially ALI. We then present advancements in the development of potential drugs for ALI targeting neuroimmune interactions, including cholinergic anti-inflammatory pathway, sympathetic-immune pathway, purinergic signalling, neuropeptides and renin-angiotensin system at different stages from preclinical investigation to clinical trials, including the traditional Chinese medicine.

CONCLUSION

This review highlights the importance of considering the therapeutic strategy of inflammatory diseases within a conceptual framework that integrates classical inflammatory cascade and neuroimmune circuits, so as to deepen the understanding of immune modulation and develop more sophisticated approaches to treat lung diseases represented by ALI.

KEY POINTS

The lungs present abundant nerve innervations. Neuroimmune interactions exert a modulatory effect in the onset and progression of lung inflammatory diseases, especially acute lung injury. The advancements of potential drugs for ALI targeting neuroimmune crosstalk at different stages from preclinical investigation to clinical trials are elaborated. Point out the direction for the development of neuroimmune pharmacology in the future.

MicroRNA‑200c‑3p regulates seawater‑induced acute lung injury via ANGII and ACE2/ANG1‑7 pathways

Apoptosis is a main characteristic of seawater aspiration-induced acute lung injury (ALI). The local angiotensin (ANG) system angiotensin converting enzyme (ACE)-2/ANG1-7/Mas axis and ANGII/angiotensin II receptor type 1 (AT1) play an important role in apoptosis. MicroRNA (miR)-200c-3p is involved in the regulation of the ACE-2 pathway, but its role and mechanism in seawater-induced ALI remain to be elucidated. In the present study, seawater-ALI lung tissue and cell model was established and apoptosis-related proteins, ACE2, ANGII, ANG1-7 were detected by western blotting following downregulation of miR-200c-3p. In addition, miR-200c-3p was detected by reverse transcription-quantitative PCR. The target relationship between miR-200c-3p and ACE2 was confirmed by dual-luciferase reporter assay. Seawater stimulation increased the expression of miR-200c-3p, ANGII and decreased ACE-2/ANG1-7 expression and induced changes of apoptosis-related protein expression. Apoptosis can be inhibited by AT1 blocker and abrogated by addition of ANG1-7 following seawater stimulation. In addition, inhibition of miR-200c-3p suppressed apoptosis and decreased the expression of ANGII, but increased the ACE-2/ANG1-7 expression. These results suggested that increased expression of miR-200c-3p was an important cause in seawater-induced ALI and this phenomenon was through inhibition of ACE2/ANG1-7 pathway.

The ACE2 activator diminazene aceturate ameliorates colitis by repairing the gut-vascular barrier in mice

Alleviating vascular barrier injury improves colitis. Angiotensin converting enzyme 2/angiotensin 1-7/Mas receptor (ACE2/Ang1-7/MasR) axis-related drugs have various biological properties, such as inhibition of inflammation and fibrosis, but their role in improving the gut-vascular barrier (GVB) has rarely been reported. This study aims to investigate the effects of diminazene aceturate (DIZE), an ACE2 activator, on vascular barrier damage in colitis. Mice were randomly divided into three groups: control, dextran sulfate sodium salt (DSS), and DIZE+DSS. Mice in the DSS group drank DSS for 8 days starting on day 4. Mice in the DIZE+DSS group were pregavaged with DIZE for 3 days and then drank DSS for 8 days while continuing to be gavaged with DIZE for 4 days. Mice were euthanized and samples were collected on the last day. Injury to colonic structure and colonic microvasculature was assessed by visual observation and appropriate staining. DSS-induced colonic and microvascular pathological damage in mice was substantially reversed by DIZE treatment. Molecular pathways were investigated by Western blot, quantitative real-time polymerase chain reaction (qRT-PCR), and enzyme linked immunosorbent assay (ELISA). DSS treatment upregulated angiotensin converting enzyme (ACE), angiotensin type 1 receptor (AT1R) protein, pro-inflammatory cytokines and inhibited tight junction-related protein expression. DIZE treatment activated ACE2/MasR protein expression and reversed epithelial barrier damage and inflammatory infiltration during DSS injury. In addition, DIZE treatment inhibited vascular endothelial growth factor A/vascular endothelial growth factor receptor 2/proto-oncogene tyrosine-protein kinase Src (VEGFA/VEGFR2/Src) pathway activation and restored vascular adhesion-linker protein vascular endothelial cadherin (VE-cadherin) expression during DSS injury. In conclusion, DIZE treatment ameliorated colitis, which was associated with balancing the two axes of the renin-angiotensin system (RAS) and repairing the GVB injury.

Targeting the renin angiotensin system for respiratory diseases

Renin-angiotensin system (RAS) plays an indispensable role in regulating blood pressure through its effects on fluid and electrolyte balance. As an aside, cumulative evidence from experimental to clinical studies supports the notion that dysregulation of RAS contributes to the pro-inflammatory, pro-oxidative, and pro-fibrotic processes that occur in pulmonary diseases like asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute lung injury (ALI). Pharmacological intervention of the various RAS components can be a novel therapeutic strategy for the treatment of these respiratory diseases. In this chapter, we first give a recent update on the RAS, and then compile, review, and analyse recent reports on targeting RAS components as treatments for respiratory diseases. Inhibition of the pro-inflammatory renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and Ang II type 1 receptor (AT1R) axis, and activation of the protective ACE2, AT2R, Ang (1-7), and Mas receptor axis have demonstrated varying degrees of efficacies in experimental respiratory disease models or in human trials. The newly identified alamandine/Mas-related G-protein-coupled receptor member D pathway has shown some therapeutic promise as well. However, our understanding of the RAS ligand-and-receptor interactions is still inconclusive, and the modes of action and signaling cascade mediating the newly identified RAS receptors remain to be better characterized. Clinical data are obviously lacking behind the promising pre-clinical findings of certain well-established molecules targeting at different pathways of the RAS in respiratory diseases. Translational human studies should be the focus for RAS drug development in lung diseases in the next decade.

ACE2/ANG-(1-7)/Mas receptor axis activation prevents inflammation and improves cognitive functions in streptozotocin induced rat model of Alzheimer's disease-like phenotypes

Activation of the renin-angiotensin system (RAS), by Angiotensin converting enzyme/Angiotensin II/Angiotensin receptor-1 (ACE/Ang II/AT1 R) axis elicits amyloid deposition and cognitive impairment. Furthermore, ACE2 induced release of Ang-(1-7) binds with the Mas receptor and autoinhibits ACE/Ang II/AT1 axis activation. Inhibition of ACE by perindopril has been reported to improve memory in preclinical settings. However, the functional significance and mechanism by which ACE2/Mas receptor regulate cognitive functions and amyloid pathology is not known. The present study is aimed to determine the role of ACE2/Ang-(1-7)/Mas receptor axis in STZ induced rat model of Alzheimer's disease (AD). We have used pharmacological, biochemical and behavioural approaches to identify the role of ACE2/Ang-(1-7)/Mas receptor axis activation on AD-like pathology in both in vitro and invivo models. STZ treatment enhances ROS formation, inflammation markers and NFκB/p65 levels which are associated with reduced ACE2/Mas receptor levels, acetylcholine activity and mitochondrial membrane potential in N2A cells. DIZE mediated ACE2/Ang-(1-7)/Mas receptor axis activation resulted in reduced ROS generation, astrogliosis, NFκB level and inflammatory molecules and improved mitochondrial functions along with Ca²⁺ influx in STZ treated N2A cells. Interestingly, DIZE induced activation of ACE2/Mas receptor significantly restored acetylcholine levels and reduced amyloid-beta and phospho-tau deposition in cortex and hippocampus that resulted in improved cognitive function in STZ induced rat model of AD-like phenotypes. Our data indicate that ACE2/Mas receptor activation is sufficient to prevented cognitive impairment and progression of amyloid pathology in STZ induced rat model of AD-like phenotypes. These findings suggest the potential role of ACE2/Ang-(1-7)/Mas axis in AD pathophysiology by regulating inflammation cognitive functions.

Ganoderma lucidum polysaccharides ameliorate lipopolysaccharide-induced acute pneumonia via inhibiting NRP1-mediated inflammation

CONTEXT

Ganoderma lucidum polysaccharides (GLP), from Ganoderma lucidum (Leyss. ex Fr.) Karst. (Ganodermataceae), are reported to have anti-inflammatory effects, including anti-neuroinflammation and anti-colitis. Nevertheless, the role of GLP in acute pneumonia is unknown.

OBJECTIVE

To explore the protective role of GLP against LPS-induced acute pneumonia and investigate possible mechanisms.

MATERIALS AND METHODS

GLP were extracted and used for high-performance liquid chromatography (HPLC) analysis after acid hydrolysis and PMP derivatization. Sixty C57BL/6N male mice were randomly divided into six groups: Sham, Model, LPS + GLP (25, 50 and 100 mg/kg/d administered intragastrically for two weeks) and LPS + dexamethasone (6 mg/kg/d injected intraperitoneally for one week). Acute pneumonia mouse models were established by intratracheal injection of LPS. Haematoxylin and eosin (H&E) staining was examined to evaluate lung lesions. ELISA and quantitative real-time PCR were employed to assess inflammatory factors expression. Western blots were carried out to measure Neuropilin-1 expression and proteins related to apoptosis and autophagy.

RESULTS

GLP suppressed inflammatory cell infiltration. In BALF, cell counts were 1.1 × 10⁶ (model) and 7.1 × 10⁵ (100 mg/kg). Release of GM-CSF and IL-6 was reduced with GLP (25, 50 and 100 mg/kg) treatment. The expression of genes IL-1β, IL-6, TNF-α and Saa3 was reduced. GLP treatment also suppressed the activation of Neuropilin-1 (NRP1), upregulated the levels of Bcl2/Bax and LC3 and led to downregulation of the ratio C-Caspase 3/Caspase 3 and P62 expression.

DISCUSSION AND CONCLUSIONS

GLP could protect against LPS-induced acute pneumonia through multiple mechanisms: blocking the infiltration of inflammatory cells, inhibiting cytokine secretion, suppressing NRP1 activation and regulating pneumonocyte apoptosis and autophagy.