Autophagy is involved in the acute lung injury induced by H9N2 influenza virus

A double-edged sword in antiviral defence: ATG7 binding dicer to promote virus replication

RNA interference (RNAi) and autophagy are two pivotal biological processes that regulate virus replication. This study explored the complex relationship between autophagy and RNAi in controlling influenza virus replication. Initially, we reported that influenza virus (H9N2) infection increases the viral load and the expression of autophagy markers while inhibiting the RNAi pathway. Subsequent studies employing autophagy enhancer and inhibitor treatments confirmed that avian influenza virus (AIV, H9N2) promotes viral replication by enhancing autophagy pathways. Further analysis revealed that ATG7, an autophagy protein, can interact with dicer to affect its antiviral functions. Finally, we discovered that infection with other avian RNA viruses, including infectious bursal disease virus (IBDV) and infectious bronchitis virus (IBV), induced the upregulation of ATG7, which blocked the RNAi pathway to facilitate virus replication. Our findings suggested that virus infection might trigger the upregulation of autophagy and downregulation of the RNAi pathway, revealing a complex interaction between these two biological processes in the defence against viral replication.

TRPM2 deficiency ameliorated H9N2 influenza virus-induced acute lung injury in mice

Oxidative stress is involved in lung damage induced by the influenza virus. The transient receptor potential melastatin-2 (TRPM2) cation channel, a Ca2+ permeable non-selective cation channel, is implicated in the mediation of multiple tissue injuries induced by oxidative stress. The role of TRPM2 in several diseases has been widely studied, but there have been few studies on the involvement of TRPM2 in lung injury induced by the H9N2 influenza virus. We investigated the effects of TRPM2 on pathological alterations, oxidative stress, apoptosis, and inflammation in mice infected with H9N2 virus. TRPM2 knockout (TRPM2-/-) mice and wild-type (WT) mice were infected separately with H9N2 influenza virus. Pulmonary oedema, lung permeability, Ca2+ concentration, redox imbalance, apoptosis, and levels of inflammatory factors (IL-1β, IL-6, TNF-α) were increased in WT mice infected with H9N2 virus. However, these effects were diminished by TRPM2 knockout. Our results emphasised the significance of TRPM2 knockdown in mitigating pathological lung alterations, maintaining Ca2+ homeostasis, reducing oxidative damage, preventing apoptosis, and suppressing the production of inflammatory cytokines in H9N2 virus-infected mice. Therefore, inhibition of TRPM2 activation is a potentially important therapeutic strategy for treating lung injury.

Tanreqing Injection Inhibits Activation of NLRP3 Inflammasome in Macrophages Infected with Influenza A Virus by Promoting Mitophagy

OBJECTIVE

To investigate the inhibitory effect of Tanreqing Injection (TRQ) on the activation of nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3) inflammasome in macrophages infected with influenza A virus and the underlying mechanism based on mitophagy pathway.

METHODS

The inflammatory model of murine macrophage J774A.1 induced by influenza A virus [strain A/Puerto Rico/8/1934 (H1N1), PR8] was constructed and treated by TRQ, while the mitochondria-targeted antioxidant Mito-TEMPO and autophagy specific inhibitor 3-methyladenine (3-MA) were used as controls to intensively study the anti-inflammatory mechanism of TRQ based on mitophagy-mitochondrial reactive oxygen species (mtROS)-NLRP3 inflammasome pathway. The levels of NLRP3, Caspase-1 p20, microtubule-associated protein 1 light chain 3 II (LC3II) and P62 proteins were measured by Western blot. The release of interleukin-1β (IL-1β) was tested by enzyme linked immunosorbent assay, the mtROS level was detected by flow cytometry, and the immunofluorescence and co-localization of LC3 and mitochondria were observed under confocal laser scanning microscopy.

RESULTS

Similar to the effect of Mito-TEMPO and contrary to the results of 3-MA treatment, TRQ could significantly reduce the expressions of NLRP3, Caspase-1 p20, and autophagy adaptor P62, promote the expression of autophagy marker LC3II, enhance the mitochondrial fluorescence intensity, and inhibit the release of mtROS and IL-1β (all P<0.01). Moreover, LC3 was co-localized with mitochondria, confirming the type of mitophagy.

CONCLUSION

TRQ could reduce the level of mtROS by promoting mitophagy in macrophages infected with influenza A virus, thus inhibiting the activation of NLRP3 inflammasome and the release of IL-1β, and attenuating the inflammatory response.

Baicalin reduced injury of and autophagy-related gene expression in RAW264.7 cells infected with H6N6 avian influenza virus

In the present study, we investigated whether baicalin could reduce the damage caused to RAW264.7 cells following infection with H6N6 avian influenza virus. In addition, we studied the expression of autophagy-related genes. The morphological changes in cells were observed by hematoxylin and eosin (H&E) staining, and the inflammatory factors in the cell supernatant were detected by enzyme-linked immunosorbent assay (ELISA). Transmission electron microscopy (TEM) was used to detect the levels of RAW264.7 autophagosomes, and western blotting and immunofluorescence were used to detect the protein expression of autophagy marker LC3. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was used to detect the mRNA transcription levels of autophagy key factors. The results showed that different doses of baicalin significantly reduced the H6N6 virus-induced damage of RAW264.7 cells. The contents of interleukin (IL)-1β, IL-2, IL-6, and tumor necrosis factor (TNF)-α in the cell supernatant significantly decreased. In addition, the protein expression of LC3 and Beclin-1, ATG12, ATG5 the mRNA levels were significantly decreased. This study showed that baicalin can reduce cell damage and affect the H6N6-induced autophagy level of RAW264.7 cells.

Autophagy in sepsis-induced acute lung injury: Friend or foe?

Sepsis-induced acute lung injury (ALI) is a life-threatening syndrome with high mortality and morbidity, resulting in a heavy burden on family and society. As a key factor that maintains cellular homeostasis, autophagy is regarded as a self-digesting process by which damaged organelles and useless proteins are recycled for cell metabolism, and it thus plays a crucial role during physiological and pathological processes. Recent studies have indicated that autophagy is involved in the pathophysiological process of sepsis-induced ALI, including cell apoptosis, inflammation, and mitochondrial dysfunction, which indicates that regulating autophagy may be beneficial for this disease. However, the role of autophagy in the etiology and treatment of sepsis-induced ALI is not well characterized. This review summarizes the autophagy-related signaling pathways in sepsis-induced ALI, as well as focuses on the dual role of autophagy and its regulation by non-coding RNAs during disease progression, for the development of potential therapeutic strategies in this disease.

Tandem mass tag-based quantitative proteomics analysis reveals the new regulatory mechanism of progranulin in influenza virus infection

Progranulin (PGRN) plays an important role in influenza virus infection. To gain insight into the potential molecular mechanisms by which PGRN regulates influenza viral replication, proteomic analyzes of whole mouse lung tissue from wild-type (WT) versus (vs) PGRN knockout (KO) mice were performed to identify proteins regulated by the absence vs. presence of PGRN. Our results revealed that PGRN regulated the differential expression of ALOX15, CD14, CD5L, and FCER1g, etc., and also affected the lysosomal activity in influenza virus infection. Collectively these findings provide a panoramic view of proteomic changes resulting from loss of PGRN and thereby shedding light on the functions of PGRN in influenza virus infection.

PI3K/AKT-mediated autophagy inhibition facilitates mast cell activation to enhance severe inflammatory lung injury in influenza A virus- and secondary Staphylococcus aureus-infected mice

Influenza A virus infection causes considerable morbidity and mortality each year globally, and secondary bacterial infection further exacerbates the severity and fatality of the initial viral infection. Mast cells have substantial roles in protecting the respiratory tract mucosa, while their role in viral and bacterial co-infection remains unclear. The present study revealed that secondary Staphylococcus aureus infection significantly aggravated the activation of mast cells during the initial H1N1 infection both in vivo and in vitro, which was closely related to the increased inflammatory lung injury and mortality. Meanwhile, the secondary S. aureus infection suppressed autophagy and promoted inflammatory mediators released by mast cells through activating the PI3K/Akt signaling pathway. Blocking PI3K/Akt pathway by LY294002, an inhibitor of Akt phosphorylation, could rescue autophagy and inhibit the release of inflammatory mediators. Furthermore, based on the influenza A viral and secondary bacterial infected mice model, we showed that the combination of LY294002 and antiviral drug oseltamivir could effectively reduce the inflammatory damage and pro-inflammatory cytokines releasing in lungs, recovering body weight loss and improving the survival rate from the co-infections. In conclusion, secondary bacterial infection can inhibit autophagy and stimulate mast cell activation through the PI3K/Akt pathway, which might explain why secondary bacterial infection would cause severe and fatal consequences following an initial influenza A viral infection.

TM9SF1 knockdown decreases inflammation by enhancing autophagy in a mouse model of acute lung injury

TM9SF1 is a member of the TM9SF (Transmembrane 9 Superfamily Member) family, which usually has a long N-terminal extracellular region and nine transmembrane domains. TM9SF1's biological function and mechanisms in inflammation are yet unknown. Tm9sf1 was shown to be upregulated in the lung tissues of mice suffering from LPS-induced acute lung injury (ALI). Tm9sf1 knockout mice were studied, and it was shown that Tm9sf1 knockout significantly alleviated LPS-induced ALI, as evidenced by higher survival rate, improved pulmonary vascular permeability, decreased inflammatory cell infiltration, and downregulated inflammatory cytokines. TM9SF1 was also demonstrated to be a negative regulator of autophagy in the LPS-induced ALI model in vitro and in vivo. The autophagy inhibitor 3-MA could counteract the beneficial effects of Tm9sf1 knockout on ALI. Therefore, we discover for the first time the role and mechanism of TM9SF1 in LPS-induced ALI and establish a relationship between TM9SF1 regulated autophagy and ALI progression, which may provide novel targets for the treatment of ALI.

The battle for autophagy between host and influenza A virus

Influenza A virus (IAV) is an infectious pathogen, threatening the population and public safety with its epidemics. Therefore, it is essential to better understand influenza virus biology to develop efficient strategies against its pathogenicity. Autophagy is an important cellular process to maintain cellular homeostasis by cleaning up the hazardous substrates in lysosome. Accumulating research has also suggested that autophagy is a critical mechanism in host defense responses against IAV infection by degrading viral particles and activating innate or acquired immunity to induce viral clearance. However, IAV has conversely hijacked autophagy to strengthen virus infection by blocking autophagy maturation and further interfering host antiviral signalling to promote viral replication. Therefore, how the battle for autophagy between host and IAV is carried out need to be known. In this review, we describe the role of autophagy in host defence and IAV survival, and summarize the role of influenza proteins in subverting the autophagic process as well as then concentrate on how host utilize antiviral function of autophagy to prevent IAV infection.

Arctiin suppresses H9N2 avian influenza virus-mediated inflammation via activation of Nrf2/HO-1 signaling

BACKGROUND

H9N2 avian influenza viruses (AIVs) infect avian and mammalian hosts and provide internal genes for new emerging highly pathogenic avian viruses that cause severe pneumonia with high mortality, for which few medications are available. Arctiin, a bioactive lignan glycoside, has been reported to possess multiple pharmacological properties. However, the effect of arctiin on H9N2 virus infection is unclear. In the current study, we analyzed the effect of arctiin on H9N2 virus infection and the underlying molecular mechanism in vitro.

METHODS

The antiviral effect against H9N2 virus was determined by plaque reduction assay (PRA) and progeny virus reduction assay. We employed MTT assay, qRT-PCR, ELISA, immunofluorescence and Western blotting to better understand the anti-inflammatory effect and corresponding mechanism of arctiin on H9N2 virus-infected cells.

RESULTS

The results showed that arctiin had antiviral activity against H9N2 virus. Arctiin treatment reduced H9N2 virus-triggered proinflammatory cytokines, such as IL-6, and TNF-α. Moreover, arctiin significantly suppressed H9N2 virus-mediated expression of COX-2 and PGE₂. Furthermore, we found that arctiin inhibited H9N2 virus-mediated activation of RIG-I/JNK MAPK signaling. Interestingly, arctiin treatment obviously reversed H9N2 virus-induced reduction of Nrf2, increased the nuclear translocation of Nrf2, and upregulated Nrf2 signaling target genes (HO-1 and SOD2). Zinc protoporphyrin (Znpp)-an HO-1 inhibitor-weakened the inhibitory effect of arctiin on H9N2 virus-induced RIG-I/JNK MAPK and proinflammatory mediators.

CONCLUSION

Taken together, these results suggested that the anti-inflammatory effects of arctiin on H9N2 virus infection may be due to the activation of Nrf2/HO-1 and blocked RIG-I/JNK MAPK signaling; thus, arctiin may be a promising agent for prevention and treatment of H9N2 virus infections.

Targeting Multiple Signal Transduction Pathways of SARS-CoV-2: Approaches to COVID-19 Therapeutic Candidates

Due to the complicated pathogenic pathways of coronavirus disease 2019 (COVID-19), related medicinal therapies have remained a clinical challenge. COVID-19 highlights the urgent need to develop mechanistic pathogenic pathways and effective agents for preventing/treating future epidemics. As a result, the destructive pathways of COVID-19 are in the line with clinical symptoms induced by severe acute coronary syndrome (SARS), including lung failure and pneumonia. Accordingly, revealing the exact signaling pathways, including inflammation, oxidative stress, apoptosis, and autophagy, as well as relative representative mediators such as tumor necrosis factor-α (TNF-α), nuclear factor erythroid 2-related factor 2 (Nrf2), Bax/caspases, and Beclin/LC3, respectively, will pave the road for combating COVID-19. Prevailing host factors and multiple steps of SARS-CoV-2 attachment/entry, replication, and assembly/release would be hopeful strategies against COVID-19. This is a comprehensive review of the destructive signaling pathways and host-pathogen interaction of SARS-CoV-2, as well as related therapeutic targets and treatment strategies, including potential natural products-based candidates.

Inhibition of Glycogen Synthase Kinase 3β Alleviates Chronic Renal Allograft Dysfunction in Rats

BACKGROUND

Chronic renal allograft dysfunction (CRAD) is a major condition that impedes the long-term survival of renal allografts. However, the mechanism of CRAD is obscure, and the effective strategies for controlling the progression of CRAD are lacking. The present study used a CRAD rat model to assess the effect of glycogen synthase kinase 3β (GSK-3β) inhibition on the development of CRAD.

METHODS

A classical F334-to-LEW orthotopic renal transplantation was performed on the CRAD group. The treatment group was treated with the GSK-3β inhibitor 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione for 12 consecutive weeks following renal transplantation. The study included uninephrectomized F344 and Lewis rats as control subjects. Twelve weeks post surgery, the rats were retrieved for analysis of renal function, urine protein levels, histological, immunohistochemical, and molecular biological parameters.

RESULTS

Administration of 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione inactivated GSK-3β and thereby improved renal function, attenuated proteinuria, and reduced renal tissue damage in CRAD rats. Besides, inactivation of GSK-3β inhibited nuclear factor-κB activation, macrophage infiltration, and expression of multiple proinflammatory cytokines/chemokines. Inhibition of GSK-3β also decreased the levels of malondialdehyde, increased superoxide dismutase levels, upregulated the expression of heme oxygenase-1 and NAD(P)H quinone oxidoreductase-1, and enhanced nuclear translocation of nuclear factor erythroid 2-related factor 2 in the kidneys of CRAD rats.

CONCLUSIONS

Inhibition of GSK-3β attenuates the development of CRAD by inhibiting inflammation and oxidant stress. Thus, GSK-3β inhibition may represent a potential therapeutic strategy for the prevention and treatment of CRAD.

Astragaloside IV attenuates IL-1β secretion by enhancing autophagy in H1N1 infection

Excessive secretion of inflammatory factors (cytokine storm) plays a significant role in H1N1-induced acute pneumonia, and autophagy acts as a cell-intrinsic mechanism to regulate inflammation. Astragaloside IV (AS-IV), originating from the astragalus root, possesses multiple pharmacological activities, such as anti-inflammation. However, the influences of AS-IV on H1N1-induced autophagy and inflammation have remained elusive. It has been reported that H1N1 infection leads to the accumulation of autophagosomes but obstructs autophagosomes incorporating into lysosomes, whereas the present study showed that AS-IV enhanced autophagy activation in H1N1 infection. Furthermore, we found that AS-IV promoted H1N1-triggered formation of autophagosomes and autolysosomes. Additionally, it was noted that AS-IV did not affect viral replication, mRNA level of interleukin-1 beta (IL-1β) and pro-IL-1β protein level, but significantly decreased secretion of IL-1β, and chloroquine (CQ, as an inhibitor of autophagy) increased secretion of IL-1β in H1N1 infection. In conclusion, AS-IV stimulates the formation of autophagosomes and the fusion of autophagosomes and lysosomes in H1N1 infection and may lead to decreased IL-1β secretion.

The active GLP-1 analogue liraglutide alleviates H9N2 influenza virus-induced acute lung injury in mice

Influenza virus is responsible for significant morbidity and mortality worldwide. Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is the major cause of death in influenza virus infected patients. Recent studies indicated that active glucagon like peptide-1 (GLP-1) encoded by glucagon (GCG) gene exerts anti-inflammatory functions. The aim of this study was to determine the potential role of active GLP-1 in H9N2 influenza virus-induced ALI/ARDS in mice. First, we uncovered that GCG mRNA expression levels and GCG precursor protein levels were significantly increased, but total GLP-1 and active GLP-1 levels were decreased in the lungs of H9N2-infected mice. Next, liraglutide, an active GLP-1 analogue, was used to treat infected mice and to observe its effects on H9N2 virus-induced ALI. Liraglutide treatment ameliorated the declined body weight, decreased food intake and mortality observed in infected mice. It also alleviated the severity of lung injury, including lowering lung index, decreasing inflammatory cell infiltration and lowing total protein levels in bronchoalveolar lavage fluid (BALF). In addition, liraglutide did not influence viral titers in infected lungs, but decreased the levels of interleukin-1β, interleukin-6 and tumor necrosis factor-α in BALF. These results indicated that liraglutide alleviated H9N2 virus-induced ALI in mice most likely due to lower levels of pro-inflammatory cytokines.

Molecular characterization and pathogenesis of H9N2 avian influenza virus isolated from a racing pigeon

H9N2 avian influenza viruses (AIVs) can cross species barriers and expand from birds tomammals and humans. It usually leads to economic loss for breeding farms and poses a serious threat to human health.This study investigated the molecular characteristics of H9N2 AIV isolated from a racing pigeon and its pathogenesis in BALB/c mice and pigeons. Phylogenetic analysis indicated that the H9N2 virus belonged to the Ck/BJ/94-like lineage, and acquired multiple specific amino acid substitutions that might contribute to viral transmission from birds to mammals and humans. A pathogenesis study showed that both mice and pigeons infected with H9N2 virus showed clinical signs and mortality. The H9N2 viruses efficiently replicated in mice and pigeons. In our study, high levels of viral shedding were detected in pigeons, but the infection was not transmitted to co-housed pigeons. Histopathological examination revealed the presence of inflammatory responses in the infected mice and pigeons. Immunohistochemical analysis showed the presence of H9N2 virus in multiple organs of the infected mice and pigeons. Moreover, the infected mice and pigeons demonstrated significant cytokine/chemokine production. Our results showed that the H9N2 virus can infect mice and pigeons, and can not be transmitted between pigeons through direct contact.