Neem leaf glycoprotein suppresses regulatory T cell mediated suppression of monocyte/macrophage functions

NLGP regulates RGS5-TGFβ axis to promote pericyte-dependent vascular normalization during restricted tumor growth

Altered RGS5-associated intracellular pericyte signaling and its abnormal crosstalk with endothelial cells (ECs) result chaotic tumor-vasculature, prevent effective drug delivery, promote immune-evasion and many more to ensure ultimate tumor progression. Moreover, the frequency of lethal-RGS5^high  pericytes within tumor was found to increase with disease progression, which signifies the presence of altered cell death pathway within tumor microenvironment (TME). In this study, we checked whether and how neem leaf glycoprotein (NLGP)-immunotherapy-mediated tumor growth restriction is associated with modification of pericytes' signaling, functions and its interaction with ECs. Analysis of pericytes isolated from tumors of NLGP treated mice suggested that NLGP treatment promotes apoptosis of NG2⁺ RGS5^high -fuctionally altered pericytes by downregulating intra-tumoral TGFβ, along with maintenance of more matured RGS5^neg  pericytes. NLGP-mediated inhibition of TGFβ within TME rescues binding of RGS5 with Gαi and thereby termination of PI3K-AKT mediated survival signaling by downregulating Bcl2 and initiating pJNK mediated apoptosis. Limited availability of TGFβ also prevents complex-formation between RGS5 and Smad2 and rapid RGS5 nuclear translocation to mitigate alternate immunoregulatory functions of RGS5^high  tumor-pericytes. We also observed binding of Ang1 from pericytes with Tie2 on ECs in NLGP-treated tumor, which support re-association of pericytes with endothelium and subsequent vessel stabilization. Furthermore, NLGP-therapy- associated RGS5 deficiency relieved CD4⁺  and CD8⁺ T cells from anergy by regulating 'alternate-APC-like' immunomodulatory characters of tumor-pericytes. Taken together, present study described the mechanisms of NLGP's effectiveness in normalizing tumor-vasculature by chiefly modulating pericyte-biology and EC-pericyte interactions in tumor-host to further strengthen its translational potential as single modality treatment.

Neem leaf glycoprotein salvages T cell functions from Myeloid-derived suppressor cells-suppression by altering IL-10/STAT3 axis in melanoma tumor microenvironment

Myeloid-derived suppressor cells (MDSCs) suppress antitumor immune functions. We have observed that an immunomodulator, neem leaf glycoprotein (NLGP), inhibits tumor-resident MDSCs and enhances antitumor CD8+ T cell immunity. NLGP inhibits the number as well as functions of tumor-resident MDSCs (Gr1±CD11b±) and enhances antitumor CD8± T cell immunity by downregulating arginase 1 and inducible nitric oxide synthase production in MDSCs. Accordingly, decreased T cell anergy and helper to regulatory T cell conversion have been observed in the presence of NLGP, which ultimately augments T cell functions. Mechanistically, NLGP-mediated rectification of T cell suppressive functions of MDSCs was primarily associated with downregulation of the interleukin (IL)-10/signal transducer and activator of transcription 3 (STAT3) signaling axis within the tumor microenvironment, as confirmed by knockdown of STAT3 (by STAT3-siRNA) and using IL-10-/- mice. Thus, NLGP-mediated suppression of MDSC functions in tumor hosts is appeared to be another associated effective mechanism for the eradication of murine melanoma by NLGP.

Neem Leaf Glycoprotein Restrains VEGF Production by Direct Modulation of HIF1α-Linked Upstream and Downstream Cascades

Neem Leaf Glycoprotein (NLGP) is a natural immunomodulator, have shown sustained tumor growth restriction as well as angiogenic normalization chiefly by activating CD8⁺ T cells. Here, we have investigated the direct role of NLGP as a regulator of tumor microenvironmental hypoxia and associated vascular endothelial growth factor (VEGF) production. We observed a significant reduction in VEGF level in both in vivo murine tumor and in vitro cancer cells (B16Mel, LLC) and macrophages after NLGP treatment. Interestingly, NLGP mediated VEGF downregulation in tumor cells or macrophages within hypoxic chamber was found at an early 4 h and again at late 24 h in mRNA level. Our data suggested that NLGP prevented hypoxia-induced strong binding of HIF1α with its co-factors, CBP/p300 and Sp3, but not with Sp1, which eventually limit the binding of HIF1α-transcriptional complex to hypoxia responsive element of VEGF promoter and results in restricted early VEGF transcription. On the otherhand, suppressed phosphorylation of Stat3 by NLGP results reduction of HIF1α at 24 h of hypoxia that further support sustained VEGF down-regulation. However, NLGP fails to regulate VHL activity as observed by both in vivo and in vitro studies. Therefore, this study for the first time reveals a mechanistic insight of NLGP mediated inhibition of angiogenesis by suppressing VEGF, which might help in vascular normalization to influence better drug delivery.

Neem leaf glycoprotein prevents post-surgical sarcoma recurrence in Swiss mice by differentially regulating cytotoxic T and myeloid-derived suppressor cells

Post-surgical tumor recurrence is a common problem in cancer treatment. In the present study, the role of neem leaf glycoprotein (NLGP), a novel immunomodulator, in prevention of post-surgical recurrence of solid sarcoma was examined. Data suggest that NLGP prevents tumor recurrence after surgical removal of sarcoma in Swiss mice and increases their tumor-free survival time. In NLGP-treated tumor-free mice, increased cytotoxic CD8⁺ T cells and a decreased population of suppressor cells, especially myeloid-derived suppressor cells (MDSCs) was observed. NLGP-treated CD8⁺ T cells showed greater cytotoxicity towards tumor-derived MDSCs and supernatants from the same CD8⁺ T cell culture caused upregulation of FasR and downregulation of cFLIP in MDSCs. To elucidate the role of CD8⁺ T cells, specifically in association with the downregulation in MDSCs, CD8⁺ T cells were depleted in vivo before NLGP immunization in surgically tumor removed mice and tumor recurrence was noted. These mice also exhibited increased MDSCs along with decreased levels of Caspase 3, Caspase 8 and increased cFLIP expression. In conclusion, it can be stated that NLGP, by activating CD8⁺ T cells, down regulates the proportion of MDSCs. Accordingly, suppressive effects of MDSCs on CD8⁺ T cells are minimized and optimum immune surveillance in tumor hosts is maintained to eliminate the residual tumor mass appearing during recurrence.

Tumor promoting role of anti-tumor macrophages in tumor microenvironment

Recent advances in tumor biology demand detailed analysis of the complex interaction of tumor cells with their adjacent microenvironment (tumor stroma) to understand the various mechanisms involved in tumor growth and metastasis. Mononuclear phagocytes or macrophages, a type of innate immune cells, defend the organism against infection and injury. On the otherhand, tumor associated macrophages (TAMs) constitute a significant part of the tumor-infiltrating immune cells, have been linked to the growth, angiogenesis, and metastasis of a variety of cancers, most likely through polarization of TAMs to the M2 (alternative) phenotype. Clinical and experimental evidences have shown that cancer tissues with high infiltration of TAMs are associated with poor patient prognosis and resistance to therapies, thus, targeting of TAMs in tumors is considered as a promising immunotherapeutic strategy. Depletion of M2 TAMs or 're-education' of them as anti-tumor effectors might contribute significantly to the search of new modalities in anti-cancer treatments. Basic questions on the factors responsible for homing of macrophages in tumors, mechanism of conversion of M1 to M2 TAMs, their functionality and, finally, the possible ways to target M2 TAMs are discussed.

Plant components for immune modulation targeting dendritic cells: implication for therapy

Medicinal plant utilization is as old as human life. There are thousands of herbs consumed for medicinal purposes all over the world, especially in east. Their value has not decreased over time and many modern pharmaceuticals have originated from traditional medicinal plants. Studying the reason for their influence is an attractive field of medicine. Among various types of herbs, some function via their immunomodulatory effects. Experiments have shown the regulatory influences of several plants on each type of immune cell, including T cells, B cells, dendritic cells (DCs), macrophages and NK cells. Because of the prominent role of DCs in antigen presentation as the major APC, this review summarizes the immunomodulatory effects of some plants performed through DC effects.

Comparative Anti-inflammatory Effects of Anti-arthritic Herbal Medicines and Ibuprofen

Non-steroidal anti-inflammatory drugs (NSAIDS), such as ibuprofen, are widely used over-the-counter drugs to treat arthritis, but they are often associated with side effects. Herbal medicines have been used to treat various diseases such as arthritis, but the scientific profiles are not well understood. In this study, we examined, in comparison with ibuprofen, the inhibitory effects on various inflammatory markers of the most commonly used herbal medicines to treat arthritis, boswellia (Boswellia sapindales), licorice (Glycyrrhiza glabra), guggul (Commiphora wightii), and neem (Azadirachta indica). To elicit inflammatory response, we exposed mouse myoblast C2C12 cells to lipopolysaccharide (LPS). Tumor necrosis factor-alpha (TNF-α) and monocyte chemotactic protein-1 (MCP-1), which are cytokines activated during an inflammatory response, were determined. The optimal non-toxic concentration was determined by exposing different concentrations of drugs (from 0.01 to 10 mg/mL). Cell death measurement revealed that the drug concentrations lower than 0.05 mg/mL were non-toxic concentrations for each drug, and these doses were used for the main experiments. We found that neem and licorice showed robust anti-inflammatory responses compared with ibuprofen. However, boswellia and guggul did not demonstrate significant anti-inflammatory responses. We concluded that neem and licorice are more effective than ibuprofen in suppressing LPS-induced inflammation in C2C12 cells.

Supraglottic laryngeal tumor microenvironmental factors facilitate STAT3 dependent pro-tumorigenic switch in tumor associated macrophages to render utmost immune evasion

Content of tumor microenvironment (TME) is varied greatly among different types of laryngeal tumors, namely, supraglottic, glottic and subglottic tumors. These three different TMEs shape infiltrating monocytes/macrophages toward M2 genotypes in variable degrees. Results obtained from in vitro studies demonstrated extent of expression of M2 phenotypic features on macrophages was maximum after their exposure to supraglottic laryngeal tumor cell lysates (SLTCL) than glottic or subglottic lysates. Moreover, M2 macrophages generated under influence of SLTCL show less nitric oxide production, greater IL-10: IL-12 ratio and poor antigen presentation. Co-culture of such M2 macrophages with T cells from healthy donors resulted decreased activation of T cells and T cell mediated tumor cell cytotoxicity, than, glottic or subglottic. SLTCL mediated macrophage polarization is STAT3 dependent and might be one of the major factors for severe immune paralysis leading to poor prognosis of supraglottic laryngeal tumor bearer following standard treatment.

Neem leaf glycoprotein is nontoxic to physiological functions of Swiss mice and Sprague Dawley rats: histological, biochemical and immunological perspectives

We have evaluated the toxicity profile of a unique immunomodulator, neem leaf glycoprotein (NLGP) on different physiological systems of Swiss mice and Sprague Dawley rats. NLGP injection, even in higher doses than effective concentration caused no behavioral changes in animals and no death. NLGP injection increased the body weights of mice slightly without any change in organ weights. NLGP showed no adverse effect on the hematological system. Moreover, little hematostimulation was noticed, as evidenced by increased hemoglobin content, leukocyte count and lymphocyte numbers. Histological assessment of different organs revealed no alterations in the organ microstructure of the NLGP treated mice and rats. Histological normalcy of liver and kidney was further confirmed by the assessment of liver enzymes like alkaline phosphatase, SGOT, SGPT and nephrological products like urea and creatinine. NLGP has no apoptotic effect on immune cells but induces proliferation of mononuclear cells collected from mice and rats. Number of CD4(+), CD8(+) T cells, DX5(+) NK cells, CD11b(+) macrophages and CD11c(+) dendritic cells is upregulated by NLGP without a significant change in CD4(+)CD25(+)Foxp3(+) regulatory T cells. Type 1 cytokines, like IFNγ also increased in serum with a decrease in type 2 cytokines. Total IgG content, especially IgG2a increased in NLGP treated mice. These type 1 directed changes help to create an anti-tumor immune environment that results in the restriction of carcinoma growth in mice. Accumulated evidence strongly suggests the non-toxic nature of NLGP. Thus, it can be recommended for human use in anti-cancer therapy.