Sulfated Polymannuroguluronate Research Articles

Marine Sulfated Polysaccharides as Promising Antiviral Agents: A Comprehensive Report and Modeling Study Focusing on SARS CoV-2.

SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) is a novel coronavirus strain that emerged at the end of 2019, causing millions of deaths so far. Despite enormous efforts being made through various drug discovery campaigns, there is still a desperate need for treatments with high efficacy and selectivity. Recently, marine sulfated polysaccharides (MSPs) have earned significant attention and are widely examined against many viral infections. This article attempted to produce a comprehensive report about MSPs from different marine sources alongside their antiviral effects against various viral species covering the last 25 years of research articles. Additionally, these reported MSPs were subjected to molecular docking and dynamic simulation experiments to ascertain potential interactions with both the receptor-binding domain (RBD) of SARS CoV-2’s spike protein (S-protein) and human angiotensin-converting enzyme-2 (ACE2). The possible binding sites on both S-protein’s RBD and ACE2 were determined based on how they bind to heparin, which has been reported to exhibit significant antiviral activity against SARS CoV-2 through binding to RBD, preventing the virus from affecting ACE2. Moreover, our modeling results illustrate that heparin can also bind to and block ACE2, acting as a competitor and protective agent against SARS CoV-2 infection. Nine of the investigated MSPs candidates exhibited promising results, taking into consideration the newly emerged SARS CoV-2 variants, of which five were not previously reported to exert antiviral activity against SARS CoV-2, including sulfated galactofucan (1), sulfated polymannuroguluronate (SPMG) (2), sulfated mannan (3), sulfated heterorhamnan (8), and chondroitin sulfate E (CS-E) (9). These results shed light on the importance of sulfated polysaccharides as potential SARS-CoV-2 inhibitors.

Sulfated polymannuroguluronate TGC161 ameliorates leukopenia by inhibiting CD4+ T cell apoptosis

Polysaccharides have aroused considerable interest due to their diverse biological activities and low toxicity. In this study, we evaluated the effect of marine polysaccharide sulfated polymannuroguluronate (TGC161) on the leukopenia induced by chemotherapy. It is found that TGC161 ameliorates the leukopenia. Besides, TGC161 would promote CD4+ T cell differentiation and maturation in the thymus, but does not have a significant effect on precursor cells in bone marrow. Furthermore, TGC161 inhibits CD4+ T cell apoptosis in vitro. Collectively, our findings offer a natural and harmless polysaccharide to ameliorate leukopenia.

Studies of Marine Sulfated Polymannuroguluronate on Endothelial Cell Proliferation and Endothelial Immunity and Related Mechanisms

Anti-proliferation action and enhancement of endothelial cell immunity and related mechanisms by marine sulfated polymannuroguluronate (SPMG) were investigated in the present studies. Endothelial cell proliferation was evaluated by MTT assay. Intercellular adhesion molecule-1 (ICAM-1) expression was analyzed by flow cytometry. The interaction of SPMG with basic fibroblast growth factor (bFGF) was evaluated by surface plasmon resonance. Results showed that SPMG exhibited a significant inhibitory effect against proliferation in both normal human umbilical vein endothelial cells (HUVEC) and bFGF-treated HUVEC, the action of which was completely abrogated by bFGF antibody. SPMG exerted high affinity to bFGF in a multivalent pattern, characterized by one molecule SPMG binding to 3 – 4 molecules of bFGF. Moreover, SPMG enhanced ICAM-1 expression in HUVEC and prevented and restored bFGF-treated downregulation of ICAM-1 expression in HUVEC, the expression of which was not counteracted by bFGF antibody. In conclusion, this is the first report demonstrating that SPMG exerted an anti-proliferation effect dependent on the bFGF-regulated pathway and afforded upregulatory activity on ICAM-1 expression regardless of the involvement of bFGF.

Sulfated polymannuroguluronate inhibits Tat-induced SLK cell adhesion via a novel binding site, a KKR spatial triad

Sulfated polymannuroguluronate (SPMG), a candidate anti-AIDS drug, inhibited HIV replication and interfered with HIV entry into host T lymphocytes. SPMG has high binding affinity for the transactivating factor of the HIV-1 virus (Tat) via its basic domain. However, deletion or substitution of the basic domain affected, but did not completely eliminated Tat-SPMG interactions. Here, we sought to identify other SPMG binding sites in addition to the basic domain. The potential SPMG binding sites were determined using molecular simulation and a surface plasmon resonance (SPR) based competitive inhibition assay. The effect of SPMG on Tat induced adhesion was evaluated using a cell adhesion assay. The KKR domain, a novel high-affinity heparin binding site, was identified, which consisted of a triad of Lys12, Lys41, and Arg78. The KKR domain, spatially enclosed SPMG binding site on Tat, functions as another binding domain for SPMG. Further functional evaluation demonstrated that SPMG inhibits Tat-mediated SLK cell adhesion by directly binding to the KKR region. The KKR domain is a novel high-affinity binding domain for SPMG. Our findings provide important new insights into the molecular mechanisms of SPMG and a potential therapeutic intervention for Tat-induced cell adhesion.

Sulfated polymannuroguluronate, a novel anti‐acquired immune deficiency syndrome drug candidate, decreased vulnerability of PC12 cells to human immunodeficiency virus tat protein through attenuating calcium overload

Human immunodeficiency virus (HIV)-1 infection of the central nervous system occurs in the vast majority of HIV-infected patients. HIV-associated dementia (HAD) represents the most severe form of HIV-related neuropsychiatric impairment. The pathogenesis of HAD is mediated by disruption of neuronal cell signal pathways, which ultimately triggers neuronal apoptosis. Evidence indicates that a viral gene product, the transactivator of transcription protein (Tat), takes a responsive role to these events. We herein report that sulfated polymannuroguluronate (SPMG), a novel anti-acquired immunodeficiency syndrome drug candidate now in phase II clinical trial, significantly decreased vulnerability of PC12 cells to HIV Tat protein by protecting cells from apoptosis. Furthermore, SPMG potently arrested Tat-triggered PKCdelta and PKCtheta activation and blocked the downstream apoptosis signaling pathways mediated by both ERK1/2 and caspase-3. These molecular mechanisms were attributed to the fact that SPMG reduced Tat-evoked calcium overload. These data demonstrate that SPMG might serve as a valuable therapeutic intervention for Tat-induced neuronal cell death and the subsequent pathologic events of HAD.

Sulfated polymannuroguluronate, a novel anti-AIDS drug candidate, inhibits HIV-1 Tat-induced angiogenesis in Kaposi's sarcoma cells

Kaposi's sarcoma (KS), a neoplasm often associated with iatrogenic and acquired immunosuppression, is characterized by prominent angiogenesis. Angiogenic factors released from KS and host cells and HIV viral products—the protein Tat are reported to be involved in angiogenesis. Mounting evidence further suggests that multiple angiogenic activities of Tat contribute to AIDS-associated Kaposi's sarcoma (AIDS-KS). Herein, we report that sulfated polymannuroguluronate (SPMG), a novel anti-AIDS drug candidate now undergoing phase II clinical trial, significantly eliminated Tat-induced angiogenesis in SLK cells both in vitro and in vivo. SPMG significantly and dose-dependently inhibits proliferation, migration, and tube formation by SLK cells. SPMG also dramatically arrested Tat-driven KDR phosphorylation and blocked the interaction between Tat and integrin β1, thus inhibiting the phosphorylation of the downstream kinases of FAK, paxillin and MAPKs. In addition, SPMG was noted to block the release of bFGF and VEGF from ECM. All these collectively favor an issue that SPMG functions as a promising therapeutic against Tat-induced angiogenesis and pathologic events relevant to AIDS-KS, which adds novel mechanistic profiling to the anti-AIDS action of SPMG.

Sulfated polymannuroguluronate, a novel anti‐acquired immune deficiency syndrome drug candidate, blocks neuroinflammatory signalling by targeting the transactivator of transcription (Tat) protein

Impaired inflammatory functions may be critical factors in the mechanisms of severe CNS disorders classified as the human immunodeficiency virus-1 (HIV-1)-associated dementia (HAD). Evidence indicates that a viral gene product, the transactivator of transcription protein (Tat), can markedly contribute to these events. We herein report that sulfated polymannuroguluronate (SPMG), a novel anti-acquired immunodeficiency syndrome drug candidate now in a phase II clinical trial, significantly reversed Tat-induced release of pro-inflammatory cytokines [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta) and IL-6] and dose dependently decreased the accumulation of reactive oxygen species and nitric oxide in THP-1 cells. Furthermore, SPMG potently arrested Tat-triggered protein kinase C (PKC)-dependent PKC-mu activation, and blocked the downstream extracellular-signal regulated kinase 1/2- and c-jun amino-terminal kinase-mediated signalling pathways. These molecular mechanisms could be attributed to the fact that SPMG preferentially bound to the basic domain (amino acids 47-57) of the Tat protein with high affinity (K(D) approximately 8.69 x 10(-10) m), leading to abrogation of Tat-mediated neuroinflammation and neurotoxicity. These data demonstrate that SPMG might serve as a valuable therapeutic intervention for Tat-induced profound pro-inflammatory effects in the brain, and subsequent pathologic events of HAD.

Sulfated Polymannuroguluronate, a Novel Anti-AIDS Drug Candidate, Inhibits T Cell Apoptosis by Combating Oxidative Damage of Mitochondria

Sulfated polymannuroguluronate (SPMG) has entered the phase II clinical trial as the first anti-AIDS drug candidate in China. Herein, we report that SPMG was effective at protecting T lymphocytes against apoptosis. Further studies indicated that SPMG significantly elevated mitochondrial membrane potential (MMP) of T cells; inhibited mitochondrial release of cytochrome c (cyto c) in T cells; enhanced the activities of mitochondrial enzyme complex I, III, and V; and subsequently increased ATP level and ATP/ADP ratio. In addition, SPMG potently suppressed reactive oxygen species (ROS) generation in mitochondria at cellular level and scavenged free radicals in cell-free system. The molecular mechanism underlying the ATP-involved and ROS-dependent antiapoptosis of SPMG is characterized as having been caused by its engagement with mitochondrial import receptor and ADP/ATP carrier in T-cell outer and inner mitochondrial membrane, respectively. All these might shed new light on the understanding of anti-AIDS functions of SPMG by protecting T cells of persons infected with human immunodeficiency virus.

T-cell receptor (TCR)/CD3 is involved in sulfated polymannuroguluronate (SPMG)-induced T lymphocyte activation

Sulfated polymannuroguluronate (SPMG) has entered the Phase II clinical trial as the first anti-acquired immune deficiency syndrome (AIDS) drug candidate in China. Proliferation assays showed that SPMG was effective at enhancing the proliferative response of T lymphocytes either with or without concanavalin A (ConA) stimulation. Flow cytometry (FCM) and fluorescence microscope examination revealed the significant binding of SPMG to T lymphocytes. The significant engagement of SPMG with TCR/CD3 complex was verified by competitive inhibition assay and one of the SPMG binding proteins purified by affinity chromatography from thymocyte membrane preparations was further confirmed to be CD3 component of TCR/CD3 complex via Western blotting analysis. In addition, SPMG was demonstrated to dramatically interact with ConA in a multivalent manner by surface plasmon resonance (SPR) assay. Notably, the concomitant presence of ConA and SPMG facilitated each other's binding to T cells. Together, the simultaneous interactions of SPMG with TCR/CD3 and with ConA can be highly proposed to facilitate the cross-linking of these molecules, and thus favoring costimulatory signaling, which serves to well explain the immunopotentiation and anti-human immunodeficiency virus (HIV) activities of SPMG.

Potentiation of T Cell Function by a Marine Algae-Derived Sulfated Polymannuroguluronate: In Vitro Analysis of Novel Mechanisms

Marine algae-derived sulfated polymannuroguluronate (SPMG), a candidate drug for AIDS treatment, was intraperitoneally injected into normal mice for 6 weeks, and the in vivo and in vitro mechanisms of SPMG for immunomodulation were investigated in isolated lymphocytes by MTT assay, flow cytometry, and surface plasmon resonance assay. SPMG treatment at 5 and 10 mg/kg enhanced concanavalin A (ConA)-induced T cell proliferation, cellular levels of CD69, interleukin-2 (IL-2), and interferon-γ (IFN-γ), as well as CD4/CD8 ratio, while decreasing tumor necrosis factor-α (TNF-α) level in T cells of peripheral blood mononuclear cells. In addition, 1 molecule of SPMG bound to 2/3 molecules of IL-2 with a KD of 9.53 × 10-7 M. Heparin prevented SPMG binding to IL-2 by 72.2%; thus, to a large extent, SPMG and heparin share common binding sites on IL-2. In contrast, other glycosaminoglycans (e.g., chondroitin sulfate and dermatan sulfate) had little effect on SPMG and IL-2 interaction, suggesting the requirement of a defined sequence within the sugar chain for specific recognition of IL-2. Concomitant treatment of IL-2 and SPMG augmented lymphocyte proliferation, compared with IL-2 alone; in contrast, SPMG alone had no proliferative effect. Taken together, our findings demonstrated for the first time that SPMG exerted its immunomodulation by direct activation of T cell function, accompanied by simultaneous modulation of cytokine function, which suggests that SPMG would show great promise for use in anti-AIDS therapy.

Comparative Studies of the Effects of Two Novel Sugar Drug Candidates on the CYP 1A2 and CYP 2E1 Enzymes in Different Sexed Rats Using a “Cocktail” Approach

The sex-based differences between the effects of two novel sugar-based drug candidates, a sulfated polymannuroguluronate (SPMG-911) and an acidic oligosaccharide sugar chain compound (AOSC-971), on the enzymes CYP 1A2 and CYP 2E1 were investigated. The results showed that neither SPMG-911 nor AOSC-971 have any effect on CYP1A2, while AOSC-971 induced the CYP 2E1 in male rats. The results are useful for their safety evaluation, as well as for the prediction of inter-drug interactions associated with the two drugs.

Sulfated polymannuroguluronate, a novel anti-acquired immune deficiency syndrome (AIDS) drug candidate, targeting CD4 in lymphocytes

Sulfated polymannuroguluronate (SPMG), a marine sulfated polysaccharide, has entered the Phase II clinical trial in China as the first anti-acquired immune deficiency syndrome (AIDS) drug candidate obtained from marine organisms. To determine the binding site(s) (receptors) of SPMG in lymphocytes mediating its anti-AIDS activities, fluorescein-5-isothiocyanate (FITC)-labeled SPMG was used to investigate SPMG binding to lymphocytes. Flow cytometry (FCM) and fluorescence microscopy analysis showed that the SPMG binds to lymphocytes in a rapid, specific, reversible, and saturable fashion. Several SPMG binding proteins were purified by affinity chromatography from lymphocyte membrane preparations. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting analysis revealed that a 55 kDa lymphocyte membrane protein is CD4. To characterize the SPMG and CD4 interaction, inhibition assay and surface plasmon resonance (SPR) assay were carried out. SPMG bound to CD4 in a multivalent fashion with specificity. The binding of SPMG to human lymphocyte CD4 was competitively inhibited by human soluble CD4 (hsCD4). Likewise, the binding between hsCD4 and immobilized SPMG was blocked by excess free SPMG. These results indicate that CD4 is one of the specific SPMG binding sites (receptors) in lymphocytes. The interaction between SPMG and CD4 may provide a mechanistic explanation of the immunopotentiating and anti-AIDS activities of SPMG in human immunodeficiency virus (HIV) infected individuals.

The potential molecular targets of marine sulfated polymannuroguluronate interfering with HIV-1 entry: Interaction between SPMG and HIV-1 rgp120 and CD4 molecule

The potential targets of marine sulfated polymannuroguluronate (SPMG) involved in inhibition of HIV-1 entry were investigated by surface plasmon resonance and flow cytometry. Results indicated that binding of SPMG either to soluble oligomeric rgp120 or to complexed rgp120–sCD4 mainly resided in V3 loop region. In addition, SPMG was shown to be less accessible for sCD4 when sCD4 had pre-interacted with rgp120, though SPMG per se multivalently bound to sCD4 with relatively low affinity. While the pre-incubation of SPMG with rgp120 caused a partial blockade of rgp120 binding to sCD4, suggesting that SPMG either shared common binding sites on gp120 with sCD4 or masked the docking sites of gp120 for sCD4. Taken together, V3 domain was demonstrated to be the major site mediating interaction of SPMG with complexed rgp120–sCD4. It seems likely that SPMG binds to both rgp120 and sCD4, but has less accessibility for sCD4 when sCD4 has already bound to rgp120. Nevertheless, addition of SPMG either prior to or after the interaction of rgp120 with sCD4 may suppress rgp120 binding to sCD4. The exact pattern of this trimolecular complex formation at the cell membrane-anchored virus level requires further clarification.

Studies of marine sulfated polymannuroguluronate on endothelial cell proliferation and endothelial immunity and related mechanisms.

Anti-proliferation action and enhancement of endothelial cell immunity and related mechanisms by marine sulfated polymannuroguluronate (SPMG) were investigated in the present studies. Endothelial cell proliferation was evaluated by MTT assay. Intercellular adhesion molecule-1 (ICAM-1) expression was analyzed by flow cytometry. The interaction of SPMG with basic fibroblast growth factor (bFGF) was evaluated by surface plasmon resonance. Results showed that SPMG exhibited a significant inhibitory effect against proliferation in both normal human umbilical vein endothelial cells (HUVEC) and bFGF-treated HUVEC, the action of which was completely abrogated by bFGF antibody. SPMG exerted high affinity to bFGF in a multivalent pattern, characterized by one molecule SPMG binding to 3 - 4 molecules of bFGF. Moreover, SPMG enhanced ICAM-1 expression in HUVEC and prevented and restored bFGF-treated downregulation of ICAM-1 expression in HUVEC, the expression of which was not counteracted by bFGF antibody. In conclusion, this is the first report demonstrating that SPMG exerted an anti-proliferation effect dependent on the bFGF-regulated pathway and afforded upregulatory activity on ICAM-1 expression regardless of the involvement of bFGF.