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Influenza Other Respir Viruses. 2017 September; 11(5): 457–463.
Published online 2017 July 11. doi:  10.1111/irv.12459
PMCID: PMC5596526

Curcumin alleviates macrophage activation and lung inflammation induced by influenza virus infection through inhibiting the NF‐κB signaling pathway

Abstract

Background

Influenza A viruses (IAV) result in severe public health problems with worldwide each year. Overresponse of immune system to IAV infection leads to complications, and ultimately causing morbidity and mortality.

Objective

Curcumin has been reported to have anti‐inflammatory ability. However, its molecular mechanism in immune responses remains unclear.

Methods

We detected the pro‐inflammatory cytokine secretion and nuclear factor kappa‐light‐chain‐enhancer of activated B cell (NF‐κB)‐related protein expression in human macrophages or mice infected by IAV with or without curcumin treatment.

Results

We found that the IAV infection caused a dramatic enhancement of pro‐inflammatory cytokine productions of human macrophages and mice immune cells. However, curcumin treatment after IAV infection downregulated these cytokines production in a dose‐dependent manner. Moreover, the NF‐κB has been activated in human macrophages after IAV infection, while administration of curcumin inhibited NF‐κB signaling pathway via promoting the expression of nuclear factor of kappa light polypeptide gene enhancer in B‐cells inhibitor, alpha (IκBα), and inhibiting the translocation of p65 from cytoplasm to nucleus.

Conclusions

In summary, IAV infection could result in the inflammatory responses of immune cells, especially macrophages. Curcumin has the therapeutic potentials to relieve these inflammatory responses through inhibiting the NF‐κB signaling pathway.

Keywords: acute lung injury, curcumin, inflammation, Influenza A viruses (IAV), nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB)

1. INTRODUCTION

Influenza A viruses (IAV) cause severe public health problems with worldwide each year, among which the acute respiratory distress syndrome (ARDS) or acute lung injury (ALI) result in the majority of influenza pneumonia associated death.1, 2 It is recorded that in 1918, approximately 50 million people lose their lives worldwide because of reoccurring pandemics.3 The host target cells, such as epithelial cells, have an essential role in responding to the IAV infection. In addition to this, the responses of immune cells, especially the macrophages are also important.4, 5

Airway macrophages (AMs) are among the first line of body defense upon the infection of IAV. The AMs have the ability to phagocytose virions and IAV‐infected cell, and its infection symbolizes an early stage of virus recognition by the innate immune system.6, 7 In addition to the early stage functions, macrophages were also found to modulate both the innate and adaptive immune responses at the late stages,8 as well as to be essential antigen presenting cells.9 The importance of its responses can be demonstrated by depletion of alveolar macrophages before IAV infection, which caused increased morbidity, mortality, and symptom severity.10, 11 However, the overresponse of macrophages to IAV infection also results in pathogenesis. It has been reported that the tissue damage caused by macrophages contributes to the following bacterial infections, and ultimately causing morbidity and mortality.12, 13

Inflammation is an adaptive physiological response following infection and tissue injuries. It is the results of series immune responses, and also leads to varieties of morbidities. Extensive studies showed that inflammation was correlated with altered signaling pathways, with enhanced levels of inflammatory markers, free radicals, and lipid peroxides. Inflammation has been hypothesized to play an essential role in competing infection and in wound healing.14 Thus, restriction of macrophage inflammatory responses to IAV infection has important clinical significance.

Curcumin, the major curcuminoid of the turmeric, has multiple health‐promoting biological activities.15 Curcumin was first used as an anti‐inflammatory agent since ancient times. Because of its anti‐apoptotic, anti‐oxidative, and anti‐inflammatory abilities, curcumin was then widely used for preventing or treating a variety of diseases other than inflammation.16, 17 The anti‐inflammatory properties of curcumin have been well studied. For example, it was reported that curcumin inhibited diverse signaling pathways, including NF‐ĸB, cyclinD1, Cyclooxygenase‐2 (COX‐2), tumor necrosis factor alpha (TNF‐α), signal transducer, and activator of transcription (STAT).18 Jin et al.19 found that curcumin inhibits interleukin 6 (IL‐6) and TNF‐α expression in lipopolysaccharide (LPS)‐induced BV2 microglia cell. Cho and colleagues revealed that in TNF‐α‐treated HaCaT cells, curcumin reduced interleukin‐1β (IL‐1β) and IL‐6 production via inhibiting NF‐ĸB and mitogen‐activated protein kinase (MAPK) signaling pathways.20 In addition, the analogs of curcumin, such as B06 and C66, also have anti‐inflammatory ability through inhibiting NO and TNF‐α production, and reducing mRNA expression of cytokines such as COX‐2, IL‐12, IL‐6, TNF‐κ, and IL‐1β.21, 22 Even the anti‐inflammatory ability of curcumin was well investigated, its anti‐IAV function studies are very limited. Umar et al.23 utilized turkeys to study the possible effects of curcumin on immuneresponse and pathogenesis of H9N2 avian influenza virus (AIV). They found that in cooperation with thymoquinone, curcumin could be able to dramatically improve the immune responses and restrain the pathogenesis of influenza viruses in turkeys.

In our present study, we aim to investigate whether curcumin can relieve the lung inflammation caused by IAV infection, and its possible mechanisms and therapeutic potential.

2. METHODS

2.1. Preparation and culture of human macrophages

The human mononuclear cells were separated from the peripheral blood of healthy blood donors by utilizing Ficoll‐Paque (Amersham Biosciences, Sunnyvale, CA, USA). From the peripheral mononuclear cells, the CD14+ cells were isolated using VarioMACS™ technique and anti‐CD14 microbeads (Miltenyi Biotec, Bergisch Gladbach, Germany), through high‐gradient magnetic sorting. Macrophages were then induced from CD14+ monocytes for 6 days, which were cultured in complete RPMI‐1640 medium with 10 ng/ml human macrophage colony‐stimulating factor (M‐CSF) (R&D System, Minneapolis, MN, USA). Curcumin (Sigma, St. Louis, MO, USA) was dissolved in ethanol at a concentration of 10 mmol/L as stock solution. It was further diluted in phosphate‐buffered saline (PBS, vehicle) for use.

2.2. Virus preparation and macrophages infection

IAV strain A/Taiwan/3530/2001 (H1N1) was used to infect human macrophages, while the A/Puerto Rico/8/34 (H1N1; PR/8) was used for murine infection. These IAV strains were grown in Madin‐Darby canine kidney cells (MDCK, ATCC®CCL‐34™) based on the standard protocol. Virus titer was detected according to the plaque assay on confluent MDCK cells. Macrophages were washed with phosphate‐buffered saline (PBS) and re‐suspended in 100 μL of serum‐free RPMI 1640 with IAV at indicated multiplicity of infection (MOI=1) for 1 hour at 37°C. The cells were collected by centrifugation, and the supernatant was removed. Then cells were cultured by RPMI 1640 supplemented with 10% fetal calf serum (FCS) at 37°C.

2.3. Measurements of cytokine levels by enzyme‐linked immunosorbent assay (ELISA)

ELISA kits (R&D Systems) were used for detection of TNF‐α, interferon‐alpha (IFN‐α), and IL‐6 levels in cell culture supernatant and mouse bronchoalveolar lavage fluid (BALF) according to the manufacturer's instructions.

2.4. Western blots

Cells were gently re‐suspended in 500 μL 1×Hypotonic Buffer by pipetting up and down several times, which was incubated on ice for 15 minutes. 25 μL detergent (10% NP40) was added and vortexed for 10 seconds at highest setting. The homogenate was centrifuged for 10 minutes at 1600 g at 4°C. This supernatant contains the cytoplasmic fraction. The pellet is the nuclear fraction. Nuclear pellet was re‐suspended in 50 μL complete Cell Extraction Buffer for 30 minutes on ice with vortexing at 10‐minute intervals and centrifuging for 30 minutes at 14 000 g at 4°C. The supernatant (nuclear fraction) was transferred to a clean microcentrifuge tube. Protein concentration was measured by the Bradford protein assay.

Denatured proteins were separated by 10% sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and then transferred onto polyvinylidene difluoride (PVDF) membranes (Millipore, Billerica, MA, USA). The transferred membranes were blocked with 5% milk in tris‐buffered saline Tween 20 (TBST) for 1 h at room temperature and then incubated with cyclin G2 (CCNG2) antibody (Cell Signaling Technology, Danvers, MA, USA) overnight at 4°C. The membranes were washed for three times with TBST, and incubated with horseradish peroxidase (HRP)‐conjugated secondary antibodies in TBST for 1 hour at room temperature. After three times washing with TBST, the immunoblotting signals were detected via the chemiluminescence method (ECL, Millipore).

2.5. Animal treatment

The mice were provided by the Animal Center of Nanjing Medical University and were randomly set into seven groups. Eight mice were allocated in each experimental group. Mice from group one were without any treatment, while those from the other six group were exposed by intratracheal route to 2.5 LD50 of Influenza A/Puerto Rico/8/34 (H1N1; PR/8) virus. Mice were challenged with IAV daily for consecutive 4 days. On each virus treatment day, one hour after the exposure to virus, curcumin with different dose (ranging from 0 to 400 mg/kg) was administrated to mice of different group by intraperitoneal injection. Animal studies were in accordance with the standard protocols approved by the ethic committee of The Affiliated Wuxi Second People's Hospital of Nanjing Medical University (approval number #WXSPH207).

2.6. Analysis of inflammatory cells in BAL fluid

PBS was slowly implanted into the lungs of mice and then a cannula that had been inserted into the trachea was used to withdraw the liquid. Cells were harvested by centrifugation at 500 g for 7 minutes, and the supernatants were collected and stored at −80°C until needed. Cells were counted by hemocytometer and stained with a panel of fluorescence‐conjugated antibodies (BD Biosciences, Franklin Lakes, NJ, USA). Fluorescently labeled cells were analyzed by Calibur™ flow cytometer (BD Biosciences), and the data were analyzed by CellQuest™software (BD Biosciences).

2.7. Statistical analyzes

All the experiments data were statistically analyzed and performed using Prism software package (GraphPad Software, Version 5.00, San Diego, CA, USA). All the values are expressed as mean±SD. The significance of differences between groups was analyzed by the one or two‐way analysis of variance (ANOVA) followed by the Tukey‐Kramer test.

3. RESULTS

3.1. Curcumin has no effects on macrophage viability and the percentage of IAV‐infected human macrophages

As it has been known that macrophages play an essential role in IAV infection,24 and curcumin can modulate the macrophage inflammatory responses,23, 25 we first ask whether curcumin has impact on macrophage viability under the infection of IAV. To address this question, we used curcumin of different concentration to treat IAV‐infected human macrophages. As shown in Figure 1A, the infection of IAV induced slight decrease of macrophage survival rate, and the administration of curcumin at different concentrations (ranging from 10 to 80 μmol/L) cannot rescue this IAV‐induced cell viability decrease of macrophages. To investigate whether curcumin treatment affects IAV infectivity of macrophages, we measured the intracellular IAV matrix protein 1 in macrophages after IAV infection. We found the treatment of curcumin failed to obviously impact the percentage of virus‐infected macrophages Figure 1B.

Figure 1

Curcumin treatment has no obvious effects on cell viability (A) and percentage of influenza A viruses (IAV) infection (B) in human macrophages. Cells were exposed to IAV for 1 hour and treated with curcumin at indicated concentrations (10, 20, ...

3.2. Curcumin treatment attenuates cytokine secretion in IAV‐infected human macrophages

To further investigate the effect of curcumin on IAV‐infected macrophages, we determined the secretion of the pro‐inflammatory cytokines TNF‐α, IFN‐α, and IL‐6, which contribute to the IAV‐induced inflammation. We found that at the time point of 6‐ and 24‐hour post‐infection of IAV, secretion of these cytokines showed a curcumin dose‐dependent decrease, compared with the control group which received no curcumin treatment (Figures 2A‐C). These results indicated that curcumin might have an anti‐IAV ability.

Figure 2

Curcumin treatment attenuates cytokine secretion in influenza A viruses (IAV)‐infected human macrophages at indicated time point post‐infection. Human macrophages were exposed to IAV for 1 h. Curcumin was presented in the culture ...

3.3. Curcumin suppresses cytokine production in IAV‐infected macrophages via downregulation of NF‐κB signaling pathway

It has been reported that before IAV stimulation, p38 MAPK and extracellular signal‐regulated kinases (ERK) were constitutively expressed and activated in macrophages. After IAV infection, the NF‐κB inhibitor IκBα could be phosphorylated and degraded.26 To further investigate the mechanisms involved in curcumin‐regulated cytokine production of IAV‐infected macrophages, we conducted Western blotting to detect the expression of associated proteins upon IAV infection and curcumin treatment. We found that IAV infection induced a decrease of cytosolic IκBα level, and an enhancement of phosphorylated IκBα (Figure 3A and B), indicating an activation of NF‐κB. However, administration of curcumin on IAV‐infected macrophages reversed this phenomenon, resulting in the increase in cytosolic IκBα and the decrease in its phosphorylation in the cytoplasm.

Figure 3

Effects of curcumin treatment (80 μmol/L) on NF‐κB signaling pathway in influenza A viruses (IAV)‐infected human macrophages at 6‐hour post‐infection. Human macrophages were exposed to IAV for 1 hour ...

P65 is a protein involved in NF‐κB heterodimer formation, nuclear translocation, and activation.27 It showed that IAV infection of macrophages leads to a significant decrease in cytosolic p65, while the levels of nuclear p65 increased under such condition. However, when the cells were treated with curcumin, we detected that both cytosolic p65 and nuclear p65 returned back to the resting levels (Figure 3A and B). Our results demonstrated that upon IAV infection, macrophages might be activated to secret inflammatory cytokines through activation of NF‐κB signaling pathway, while the antivirus ability of curcumin might depend on inhibition of NF‐κB in macrophages.

3.4. Curcumin inhibited the in vivo expanding of immune cells and cytokine production in mice BAL fluid upon IAV infection

To determine whether curcumin affects immune cells, mice were exposed to IAV for 1 hour and then treated with curcumin once daily for consecutive 4 days. On day 4 post‐infection, mice BAL fluid was obtained, and immune cell profiles were characterized by counting the immune cell numbers. The fluorescence‐activated cell sorting (FACS) results showed that IAV infection induced significant expanding of total cells, macrophages, neutrophils, and lymphocytes. However, curcumin could inhibit the proliferation of these immune cells in a dose‐dependent manner (Figure 4A‐D).

Figure 4

Effects of curcumin treatment on immune cell profiles in BAL fluid. Mice were treated with curcumin at indicated doses (ip injection 1 h after influenza A viruses (IAV) infection once daily for consecutive 4 days). BAL fluid was obtained ...

To demonstrate the effect of curcumin on mice BAL fluids, we detected the secretion of the pro‐inflammatory cytokines TNF‐α, IFN‐α, and IL‐6, which contribute to IAV‐induced lung inflammation. TNF‐α, IFN‐α, and IL‐6 levels were significantly elevated in the IAV‐infected groups compared with the control group, which received no IAV infection. However, treatment of curcumin dramatically reduced the secretion of TNF‐α, IFN‐α, and IL‐6 in a dose‐dependent manner (Figure 5A‐C).

Figure 5

Effects of curcumin treatment on cytokine production in BAL fluid, including TNF‐α (A), IFN‐α (B) and IL‐6 (C). Mice were treated with curcumin at indicated doses (ip injection 1 hour after influenza A viruses ...

4. DISCUSSION

The remittent explosion of pandemic influenza and appearance of novel IAV is worldwide threat. Some of the infection results in severe pneumonia or death, although majority of patients present with mild symptoms. Great efforts have been made to investigate the mechanism of pathogenesis of IAV‐induced diseases, and certain vaccines have been clinically utilized worldwide. However, the morbidity and mortality keep high.28 IAV infection is one of the reasons causing acute lung injury (ALI), which promotes the intravascular activation of inflammatory cells, and ultimately causes the injury of endothelial or parenchymal cells.29 As early as in 1995, Rogy and colleagues have demonstrated that the overexpression of TNF‐α receptor efficiently protected mice from LPS‐induced sepsis. As high levels of pro‐inflammatory cytokines play an essential role in inflammatory response, strategies to inhibit their functions or promote the impact of anti‐inflammatory cytokines have been investigated.30

Our present work reveals that upon the IAV infection, human macrophages produced significantly higher levels of pro‐inflammatory cytokines, such as TNF‐α, IFN‐α, and IL‐6, compared to that with no virus infection. The dysregulation of pro‐inflammatory cytokine production induced by IAV was further confirmed in vivo by infection of mice with IAV. The results are consistent with many other studies that upon the infection of IAV, mice produced dramatically higher levels of TNF‐α, IFN‐α, and IL‐6.30, 31 Thus, we aimed to find out an agent to inhibit the inflammatory responses of macrophages and alleviate the acute lung injury induced by IAV infection.

Curcumin is the major curcuminoid derived from turmeric, which is a member of the ginger family. It exhibits anti‐inflammatory, anti‐tumor, anti‐oxidative activities, as well as safety.32, 33 The diverse bioactivities of curcumin derive from its capability to modulate a number of signaling pathway components, such as transforming growth factor‐β, phosphorylase kinase, adhesion molecules, 5‐lipoxygenase (5‐LOX), C‐reactive protein, STAT3, pro‐inflammatory cytokines, NF‐κB, and apoptotic proteins. Moreover, different formulations of curcumin have been investigated, such as powder, tablets, capsules, emulsions, liposomal encapsulation, and even nanoparticles. In fact, in clinical trials, curcumin has been utilized alone or in cooperation with other drugs.33

In our present study, we used curcumin of different concentration to treat the IAV‐infected human macrophages and found that curcumin could neither significantly affect the viability of IAV‐infected human macrophages, nor obviously impact the percentage of virus‐infected macrophages. This indicated that curcumin has no effect on the virus‐defense ability of human macrophage, as well as the viability of these innate immune cells. However, by examining the culture medium, we found that curcumin indeed downregulate the pro‐inflammatory cytokine (TNF‐α, IFN‐α and IL‐6) production of IAV‐infected human macrophages.

We further established the in vivo mouse model by exposing the mice with IAV via intratracheal route, and then treated the mice with curcumin of certain concentrations. We tested the cytokine contents in BAL fluid and found that IAV infection resulted in the outbreak of pro‐inflammatory cytokine, such as TNF‐α, IFN‐α, and IL‐6. However, when the infected mice received curcumin administration, these pro‐inflammatory cytokines dramatically decreased in a dose‐dependent manner. It demonstrated the ability of curcumin to inhibit IAV‐induced infection via downregulating the pro‐inflammatory cytokine. When we examined the immune cell characteristics in the BAL fluid, we found that the immune cells, including macrophages, neutrophils, and lymphocytes, underwent an explosion upon the IAV infection, but soon decreased in numbers after the curcumin administration. Thus, we deduced that under the IAV challenge, curcumin exerted its anti‐inflammatory ability by both inhibiting the immune cell expanding and downregulating the pro‐inflammatory cytokine production.

Previous studies have revealed that NF‐κB signaling pathway is one of the most important pathways that are activated in macrophages under the pathogen challenge.34, 35, 36, 37, 38 Thus, we aimed to study whether the anti‐inflammatory ability of curcumin is associated with NF‐κB signaling pathway. By examining the protein expression levels via Western Blotting, we found that IAV infection leads to the decrease in IκBα and cytosolic p65, while enhanced the levels of p‐IκBα and nuclear p65. However, administration of curcumin exactly reversed this phenomenon. IκBα is a NF‐κB inhibitor that could be phosphorylated and degraded when cells suffering IAV challenge. P65 is a component of NF‐κB heterodimer, which is associated with NF‐κB nuclear translocation and activation.27 Thus, it is reasonable that when the cells are infected with IAV, IκBα underwent degradation and phosphorylation, facilitating the activation of NF‐κB. While as a component of NF‐κB heterodimer, p65 could translocate from the cytoplasm to the nuclear, to promote the expression of pro‐inflammatory‐related genes. These findings indicated that NF‐κB might be a target of curcumin to inhibit the pro‐inflammatory responses of immune cells. Our results are consistent with the anti‐atherosclerotic study of Cao et al., in which they revealed that in oxidized low‐density lipoprotein (oxLDL) stimulated macrophages, curcumin reduced the levels of CD147 and matrix metallopeptidase 9 (MMP‐9) by inhibiting the NF‐κB signaling pathways.39

In conclusion, we found that IAV infection could result in the inflammatory responses of immune cells, especially macrophages. Our results suggest that curcumin confers protection against IAV‐induced acute lung injury by limiting immune cell expanding and downregulating pro‐inflammatory cytokine production through inhibiting NF‐κB signaling pathway. The anti‐inflammatory effects of curcumin indicate that it has therapeutic potential for acute lung inflammatory disease.

CONFLICTS OF INTEREST

The authors declare that they have no conflict of interest.

ACKNOWLEDGEMENTS

None.

Notes

Xu Y, Liu L. Curcumin alleviates macrophage activation and lung inflammation induced by influenza virus infection through inhibiting the NF‐κB signaling pathway. Influenza Other Respi Viruses. 2017;11:457‐463. https://doi.org/10.1111/irv.12459

REFERENCES

1. Yokoyama T, Tsushima K, Ushiki A, et al. Acute lung injury with alveolar hemorrhage due to a novel swine‐origin influenza A (H1N1) virus. Intern Med. 2010;49:427‐430. [PubMed]
2. Ivan FX, Rajapakse JC, Welsch RE, et al. Differential pulmonary transcriptomic profiles in murine lungs infected with low and highly virulent influenza H3N2 viruses reveal dysregulation of TREM1 signaling, cytokines, and chemokines. Funct Integr Genomics. 2012;12:105‐117. [PubMed]
3. Taubenberger JK, Morens DM. 1918 Influenza: the mother of all pandemics. Emerg Infect Dis. 2006;12:15‐22. [PubMed]
4. Tate MD, Pickett DL, van Rooijen N, Brooks AG, Reading PC. Critical role of airway macrophages in modulating disease severity during influenza virus infection of mice. J Virol. 2010;84:7569‐7580. [PubMed]
5. Geiler J, Michaelis M, Sithisarn P, Cinatl J Jr. Comparison of pro‐inflammatory cytokine expression and cellular signal transduction in human macrophages infected with different influenza A viruses. Med Microbiol Immunol. 2011;200:53‐60. [PubMed]
6. Fujisawa H, Tsuru S, Taniguchi M, Zinnaka Y, Nomoto K. Protective mechanisms against pulmonary infection with influenza virus. I. Relative contribution of polymorphonuclear leukocytes and of alveolar macrophages to protection during the early phase of intranasal infection. J Gen Virol. 1987;68():425‐432. [PubMed]
7. Hashimoto Y, Moki T, Takizawa T, Shiratsuchi A, Nakanishi Y. Evidence for phagocytosis of influenza virus‐infected, apoptotic cells by neutrophils and macrophages in mice. J Immunol. 2007;178:2448‐2457. [PubMed]
8. Shi C, Pamer EG. Monocyte recruitment during infection and inflammation. Nat Rev Immunol. 2011;11:762‐774. [PubMed]
9. Junt T, Moseman EA, Iannacone M, et al. Subcapsular sinus macrophages in lymph nodes clear lymph‐borne viruses and present them to antiviral B cells. Nature. 2007;450:110‐114. [PubMed]
10. Tumpey TM, Garcia‐Sastre A, Taubenberger JK, et al. Pathogenicity of influenza viruses with genes from the 1918 pandemic virus: functional roles of alveolar macrophages and neutrophils in limiting virus replication and mortality in mice. J Virol. 2005;79:14933‐14944. [PubMed]
11. Murphy EA, Davis JM, McClellan JL, et al. Susceptibility to infection and inflammatory response following influenza virus (H1N1, A/PR/8/34) challenge: role of macrophages. J Interferon Cytokine Res. 2011;31:501‐508. [PubMed]
12. Chen WH, Toapanta FR, Shirey KA, et al. Potential role for alternatively activated macrophages in the secondary bacterial infection during recovery from influenza. Immunol Lett. 2012;141:227‐234. [PubMed]
13. Sweet MJ, Hume DA. Endotoxin signal transduction in macrophages. J Leukoc Biol. 1996;60:8‐26. [PubMed]
14. He Y, Yue Y, Zheng X, et al. Curcumin, inflammation, and chronic diseases: how are they linked? Molecules. 2015;20:9183‐9213. [PubMed]
15. Zhu J, Sanidad KZ, Sukamtoh E, Zhang G. Potential roles of chemical degradation in the biological activities of curcumin. Food Funct. 2017;8:907‐914. [PubMed]
16. Jiang S, Han J, Li T, et al. Curcumin as a potential protective compound against cardiac diseases. Pharmacol Res. 2017;119:373‐383. [PubMed]
17. Liu XF, Hao JL, Xie T, et al. Curcumin, A potential therapeutic candidate for anterior segment eye diseases: a review. Front Pharmacol. 2017;8:66. [PubMed]
18. Ghosh S, Banerjee S, Sil PC. The beneficial role of curcumin on inflammation, diabetes and neurodegenerative disease: a recent update. Food Chem Toxicol. 2015;83:111‐124. [PubMed]
19. Jin CY, Lee JD, Park C, Choi YH, Kim GY. Curcumin attenuates the release of pro‐inflammatory cytokines in lipopolysaccharide‐stimulated BV2 microglia. Acta Pharmacol Sin. 2007;28:1645‐1651. [PubMed]
20. Cho JW, Lee KS, Kim CW. Curcumin attenuates the expression of IL‐1beta, IL‐6, and TNF‐alpha as well as cyclin E in TNF‐alpha‐treated HaCaT cells; NF‐kappaB and MAPKs as potential upstream targets. Int J Mol Med. 2007;19:469‐474. [PubMed]
21. Pan Y, Wang Y, Cai L, et al. Inhibition of high glucose‐induced inflammatory response and macrophage infiltration by a novel curcumin derivative prevents renal injury in diabetic rats. Br J Pharmacol. 2012;166:1169‐1182. [PubMed]
22. Pan Y, Zhu G, Wang Y, et al. Attenuation of high‐glucose‐induced inflammatory response by a novel curcumin derivative B06 contributes to its protection from diabetic pathogenic changes in rat kidney and heart. J Nutr Biochem. 2013;24:146‐155. [PubMed]
23. Umar S, Shah MA, Munir MT, et al. Synergistic effects of thymoquinone and curcumin on immune response and anti‐viral activity against avian influenza virus (H9N2) in turkeys. Poult Sci. 2016;95:1513‐1520. [PubMed]
24. Iwasaki A, Pillai PS. Innate immunity to influenza virus infection. Nat Rev Immunol. 2014;14:315‐328. [PubMed]
25. Ou JL, Mizushina Y, Wang SY, et al. Structure‐activity relationship analysis of curcumin analogues on anti‐influenza virus activity. FEBS J. 2013;280:5829‐5840. [PubMed]
26. Huang MT, Chen ST, Wu HY, et al. DcR3 suppresses influenza virus‐induced macrophage activation and attenuates pulmonary inflammation and lethality. J Mol Med (Berl). 2015;93:1131‐1143. [PubMed]
27. Jimi E. Fukushima H [NF‐kappaB signaling pathways and the future perspectives of bone disease therapy using selective inhibitors of NF‐kappaB]. Clin Calcium. 2016;26:298‐304. [PubMed]
28. Li H, Cao B. Pandemic and avian influenza A viruses in humans: epidemiology, virology, clinical characteristics, and treatment strategy. Clin Chest Med. 2017;38:59‐70. [PubMed]
29. Artigas A, Bernard GR, Carlet J, et al. The American‐European Consensus Conference on ARDS, part 2. Ventilatory, pharmacologic, supportive therapy, study design strategies and issues related to recovery and remodeling. Intensive Care Med 1998;24:378‐398. [PubMed]
30. Hashiba T, Suzuki M, Nagashima Y, et al. Adenovirus‐mediated transfer of heme oxygenase‐1 cDNA attenuates severe lung injury induced by the influenza virus in mice. Gene Ther. 2001;8:1499‐1507. [PubMed]
31. Vogel AJ, Harris S, Marsteller N, Condon SA, Brown DM. Early cytokine dysregulation and viral replication are associated with mortality during lethal influenza infection. Viral Immunol. 2014;27:214‐224. [PubMed]
32. Li J, Luo M, Xie N, Wang J, Chen L. Curcumin protects endothelial cells against homocysteine induced injury through inhibiting inflammation. Am J Transl Res. 2016;8:4598‐4604. [PubMed]
33. Gupta SC, Patchva S, Aggarwal BB. Therapeutic roles of curcumin: lessons learned from clinical trials. AAPS J. 2013;15:195‐218. [PubMed]
34. Pang M, Yuan Y, Wang D, et al. Recombinant CC16 protein inhibits the production of pro‐inflammatory cytokines via NF‐kappaB and p38 MAPK pathways in LPS‐activated RAW264.7 macrophages. Acta Biochim Biophys Sin (Shanghai) 2017;49:435‐443. [PubMed]
35. Jiang F, Guan H, Liu D, et al. Flavonoids from sea buckthorn inhibit the lipopolysaccharide‐induced inflammatory response in RAW264.7 macrophages through the MAPK and NF‐kappaB pathways. Food Funct 2017;8:1313‐1322. [PubMed]
36. Li N, Katz S, Dutta B, et al. Genome‐wide siRNA screen of genes regulating the LPS‐induced NF‐kappaB and TNF‐alpha responses in mouse macrophages. Sci Data. 2017;4:170008. [PubMed]
37. Lee HW, Lee CG, Rhee DK, Um SH, Pyo S. Sinigrin inhibits production of inflammatory mediators by suppressing NF‐kappaB/MAPK pathways or NLRP3 inflammasome activation in macrophages. Int Immunopharmacol. 2017;45:163‐173. [PubMed]
38. Park JY, Chung TW, Jeong YJ, et al. Ascofuranone inhibits lipopolysaccharide‐induced inflammatory response via NF‐kappaB and AP‐1, p‐ERK, TNF‐alpha, IL‐6 and IL‐1beta in RAW 264.7 macrophages. PLoS One. 2017;12:e0171322. [PubMed]
39. Cao J, Ye B, Lin L, et al. Curcumin alleviates oxLDL induced MMP‐9 and EMMPRIN expression through the inhibition of NF‐kappaB and MAPK pathways in macrophages. Front Pharmacol. 2017;8:62. [PubMed]

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