Id |
Subject |
Object |
Predicate |
Lexical cue |
T58 |
0-2 |
Sentence |
denotes |
4. |
T59 |
4-45 |
Sentence |
denotes |
Mechanisms of CQ/HCQ in treating COVID-19 |
T60 |
47-51 |
Sentence |
denotes |
4.1. |
T61 |
53-71 |
Sentence |
denotes |
Antiviral activity |
T62 |
73-79 |
Sentence |
denotes |
4.1.1. |
T63 |
81-122 |
Sentence |
denotes |
Hindrance of receptor recognition process |
T64 |
123-214 |
Sentence |
denotes |
The S protein of SARS-CoV-2 is cleaved by host proteases into two subunits, S1 and S2 [19]. |
T65 |
215-398 |
Sentence |
denotes |
The S1 subunit binds to the host cell surface receptor angiotensin-converting enzyme 2 (ACE2) for virus attachment, and the S2 subunit fuses the virus and the host cell membrane [19]. |
T66 |
399-787 |
Sentence |
denotes |
The investigation of the effect of CQ on ACE2 in VeroE6 cells showed that effective anti-SARS-CoV-2 concentrations of CQ had no significant effect on the synthesis and glycosylation of S protein on the surface of SARS-CoV, and although it had no significant effect on the cell surface expression of ACE2, CQ could destroy the glycosylation at the terminal glycosylation site of ACE2 [13]. |
T67 |
788-1061 |
Sentence |
denotes |
Therefore, the mechanism of anti-CoV activity of CQ/HCQ may be at least partly related to the impairment of terminal glycosylation of ACE2, which may result in reduced binding affinities between ACE2 and SARS CoV S protein, thereby blocking receptor recognition (Figure 1). |
T68 |
1062-1071 |
Sentence |
denotes |
Figure 1. |
T69 |
1072-1190 |
Sentence |
denotes |
Schematic representation of the possible mechanisms of CQ/HCQ against CoVs replication and modulating immune response. |
T70 |
1191-1822 |
Sentence |
denotes |
CQ/HCQ may synergistically exert antiviral and immunomodulatory effects on COVID-19 through multiple mechanisms including hindering the receptor recognition process by influencing the affinity of ACE2 and S protein, and the affinity for sialic acid and ganglioside; inhibiting the membrane fusion process by suppressing endolysosome acidification; suppressing the p38 activation and affecting host defense machinery, and preventing MHC class II expression (block expression of CD154 on the surface of CD4 + T cell) and TLR signaling and reducing the production of cytokines through inhibiting the activation of T cells and B cells. |
T71 |
1823-2173 |
Sentence |
denotes |
ACE2, angiotensin-converting enzyme 2; COVID-19, coronavirus disease 2019; CQ, chloroquine; HCQ, hydroxychloroquine; CoVs, coronaviruses; MAPK, mitogen-activated protein kinase; MHC-II, major histocompatibility complex class II; TLR, toll-like receptor; cGAS, cyclic GMP-AMP synthase; IFN, interferon; IL, interleukin; TNF-α, tumor necrosis factor-α. |
T72 |
2174-2459 |
Sentence |
denotes |
In addition to protein membrane receptors, infection of host cells by HCoVs also relies on sialic acid-containing glycoproteins and gangliosides, which are used by a broad range of viruses as receptors, such as influenza [20] and HCoVs including SARS-CoV [21] and HCoV-OC43 [13,22,23]. |
T73 |
2460-2658 |
Sentence |
denotes |
A recent molecular structure analysis showed that SARS-CoV-2 not only uses ACE2 as a receptor, but also recognizes highly conserved gangliosides on the host cell surface through sialic acid [24,25]. |
T74 |
2659-2799 |
Sentence |
denotes |
CQ/HCQ binds sialic acids and gangliosides with high affinity, which can prevent the attachment of SARSCoV-2 S protein to gangliosides [25]. |
T75 |
2800-2907 |
Sentence |
denotes |
CQ had inhibitory effect on quinone reductase 2 (QR2) involved in the biosynthesis of sialic acids [26,27]. |
T76 |
2908-3059 |
Sentence |
denotes |
Hence, the mechanism of anti-CoV activity of CQ/HCQ may also be related to hindering the recognition process of sialic acid and ganglioside (Figure 1). |
T77 |
3061-3067 |
Sentence |
denotes |
4.1.2. |
T78 |
3069-3112 |
Sentence |
denotes |
Interference of the membrane fusion process |
T79 |
3113-3240 |
Sentence |
denotes |
CoVs are enveloped RNA viruses, and their cell entry processes involve a principal route of receptor-mediated endocytosis [28]. |
T80 |
3241-3405 |
Sentence |
denotes |
Membrane fusion takes place in the endosomal compartment after endocytosis, which needs additional triggers such as pH acidification or proteolytic activation [29]. |
T81 |
3406-3645 |
Sentence |
denotes |
Multiple cellular proteases, such as trypsin, furin, proprotein convertase (PC) family, cathepsins, transmembrane protease/serine (TMPRSS) proteases and elastase, are involved in S protein activation, which can induce membrane fusion [30]. |
T82 |
3646-3880 |
Sentence |
denotes |
Among them, cathepsin L, with anoptimal pH of 3.0 to 6.5, is most commonly associated with activation of a variety of CoV S proteins [30], such as SARS-CoV [19], MERS-CoV [31], HCoV-229E [32], and mouse hepatitis virus 2 (MHV-2) [33]. |
T83 |
3881-4043 |
Sentence |
denotes |
A recent study found that SARS-CoV-2 enters 293/hACE2 cells mainly through endocytosis, in which cathepsin L is critical for priming of SARS-CoV-2 S protein [24]. |
T84 |
4044-4393 |
Sentence |
denotes |
A study investigated the detailed mechanism of action of CQ/HCQ in inhibiting SARS-CoV-2 entry, and co-localization of SARS-CoV-2 with early endosomes (EEs) or endolysosomes (ELs) in VeroE6 cells, and the results showed that CQ/HCQ hampered the transport of SARS-CoV-2 from EEs to ELs, indicating that CQ/HCQ might inhibit endosomal maturation [17]. |
T85 |
4394-4657 |
Sentence |
denotes |
These studies revealed that the mechanism of anti-CoV activity of CQ/HCQ may involve the inhibition of the endosome acidification process, which might inactivate lysosomal proteases, thus interfering with the fusion of virus and host membranes [34,35] (Figure 1). |
T86 |
4659-4665 |
Sentence |
denotes |
4.1.3. |
T87 |
4667-4727 |
Sentence |
denotes |
Effects on cell signaling pathway and host defense machinery |
T88 |
4728-4904 |
Sentence |
denotes |
The mitogen-activated protein kinase (MAPK) pathway transmits signals from the cell surface to the nucleus involved in the infection of CoVs such as MHV [36] and SARS-CoV [37]. |
T89 |
4905-5044 |
Sentence |
denotes |
CQ could inhibit HCoV-229E replication in human embryonic lung epithelial cells (L132) through suppressing the activation of p38 MAPK [38]. |
T90 |
5045-5210 |
Sentence |
denotes |
Moreover, HCQ could markedly induce the production of cellular reactive oxygen species (ROS), which play an important role in the activation of innate immunity [39]. |
T91 |
5211-5368 |
Sentence |
denotes |
HCQ also could trigger the host defense mechanism through the mitochondrial antiviral signaling (MAVS) pathway, resulting in anti-dengue virus activity [39]. |
T92 |
5369-5529 |
Sentence |
denotes |
Therefore, CQ/HCQ may also exert their antiviral activity by suppressing the activation of p38 MAPK pathway and affecting the host defense machinery (Figure 1). |
T93 |
5531-5535 |
Sentence |
denotes |
4.2. |
T94 |
5537-5599 |
Sentence |
denotes |
Inhibitory effect on T cell activation and cytokine production |
T95 |
5600-5702 |
Sentence |
denotes |
CQ/HCQ regulate the release of various pro-inflammatory factors, which are important immunomodulators. |
T96 |
5703-5888 |
Sentence |
denotes |
Intracellular alkalinization by CQ/HCQ inhibits lysosomal activity, preventing antigen processing, major histocompatibility complex (MHC) class II expression and immune activation [40]. |
T97 |
5889-5999 |
Sentence |
denotes |
This process can inhibit T cell activation and block expression of CD154 on the surface of CD4 + T cells [41]. |
T98 |
6000-6132 |
Sentence |
denotes |
CQ also reduces cytokines such as interleukin (IL)-1, IL-6 and tumor necrosis factor-α (TNF-α) produced by T cells and B cells [42]. |
T99 |
6133-6323 |
Sentence |
denotes |
At the same time, changes of endosomal pH can interfere with Toll-like receptor (TLR) signaling, such as TLR7 and TLR9 processing, inhibiting the activation and production of cytokines [43]. |
T100 |
6324-6475 |
Sentence |
denotes |
CQ/HCQ also weaken the cyclic GMP-AMP (cGAMP) synthase (cGAS) activity by inhibiting cytosolic DNA, thereby reducing type I interferon production [44]. |
T101 |
6476-6624 |
Sentence |
denotes |
In vitro, CQ/HCQ can also inhibit phospholipase A2, altering the metabolism of arachidonic acid, and reducing the production of prostaglandins [45]. |
T102 |
6625-6920 |
Sentence |
denotes |
Some clinical studies have found that high concentrations of cytokines and pro-inflammatory factors such as IL-6 and IL-10 are elevated in the plasma of critically ill patients infected with SARS-CoV-2 [46,47], suggesting that cytokine release syndrome (CRS) is associated with disease severity. |
T103 |
6921-7047 |
Sentence |
denotes |
In the aspect of immune response, HCQ/CQ therefore are likely to inhibit CRS, delaying the progression of COVID-19 (Figure 1). |