Neem leaf glycoprotein optimizes effector and regulatory functions within tumor microenvironment to intervene therapeutically the growth of B16 melanoma in C57BL/6 mice

COVID-19 imparted immune manifestation can be combated by NLGP: Lessons from cancer research

SARS-CoV-2 easily infects human monocytes, macrophages and possibly dendritic cells (DCs), causing dysfunctions of these important antigen presenting cells (APCs). Observed DC dysfunctions facilitate improper antigen presentation, which obviously results T cell anergy, exhaustion and apoptosis, thus, may be contributing significantly in SARS-CoV-2 infection associated lymphopenia. Neem Leaf Glycoprotein or NLGP has enormous role in altered DC functions, thereby, offering optimum T cell mediated cytotoxicity, as experienced from cancer system. Such NLGP guided correction of altered DCs might also be effective to generate proper SARS-CoV-2-specific effector and central memory T cells.

Increased expression of co-stimulatory molecules and enhancement of the IgG response in rats orally administered with a polyherbal formulation

Background

Link Samahan® (LS) is a standardized modern formulation of a polyherbal preparation used in the indigenous system of medicine in Sri Lanka.

Objective

Evaluation of the immunostimulatory activity of LS and the molecular mechanisms that modulate the humoral immune response.

Material and methods

Immunostimulatory activity of LS was tested in rats following oral administration on days 1-5 and 15-19 and immunization with bovine serum albumin (BSA) on day 1 and 15. Anti-BSA IgM and IgG response in rats treated with LS, water and sugar (as controls) were compared on days 0-35, using ELISA. The expression of co-stimulatory molecules on lymphocytes was assessed on days 0-8 and days 14-22 using RT-qPCR.

Results

IgM and IgG levels of LS-treated rats were increased significantly by day 7 and 21 respectively compared to controls (p < 0.05). IgG response of LS-treated group reached a higher magnitude compared to its IgM response. Gene expression of CD28 and CD40L on T cells (4.9-5.1 fold) and CD80, CD86 and CD40 on APCs (2.4-3.1 fold) were induced significantly by day 2 compared to their expression on day 0 (p < 0.05). The expression levels of CD28 and CD40L on day 2-4 and 16-18 were similar while the expression of CD80, CD86 and CD40 on day 16-18 was higher (3.7-5.1 folds) compared to their levels on day 2-4 (2.4-3.2).

Conclusions

These findings support an adjuvant effect of LS contributing to its immunostimulatory activity and increased expression of co-stimulatory molecules that contribute to boosting immune response.

Exploring the role of Azadirachta indica (neem) and its active compounds in the regulation of biological pathways: an update on molecular approach

In ethnomedicine, plant parts and compounds are used traditionally to treat different diseases. Neem (Azadirachta indica A. Juss) is the most versatile and useful medicinal plant ever found. Its every part is rich in bioactive compounds, which have traditionally been used to treat different ailments including infectious diseases. Bioactive compounds such as nimbolide, azarirachtin, and gedunin of neem are reported to have a tremendous ability to regulate numerous biological processes in vitro and in vivo. The present review article aims to explore the importance of neem extracts and bioactive compounds in the regulation of different biological pathways. We have reviewed research articles up to March 2020 on the role of neem in antioxidant, anti-inflammatory, antiangiogenic, immunomodulatory, and apoptotic activities. Studies on the concerned fields demonstrate that the bioactive compounds and extracts of neem have a regulatory effect on several biological mechanisms. It has been unveiled that extensive research is carried out on limonoids such as nimbolide and azarirachtin. It is evidenced by different studies that neem extracts are the potential to scavenge free radicals and reduce ROS-mediated damage to cells. Neem can be used to normalize lipid peroxidation and minimize ROS-mediated cell death. Besides, neem extracts can significantly reduce the release of proinflammatory cytokines and elevate the count of CD4 + and CD8 + T-cells. This review indicates the pivotal roles of A. indica in the regulation of different biological pathways. However, future investigations on other bioactive compounds of neem may reveal different therapeutic potentials.

NLGP Attenuates Murine Melanoma and Carcinoma Metastasis by Modulating Cytotoxic CD8+ T Cells

Neem leaf glycoprotein (NLGP), a natural immunomodulator, attenuates murine carcinoma and melanoma metastasis, independent of primary tumor growth and alterations in basic cellular properties (cell proliferation, cytokine secretion, etc.). Colonization event of invasion–metastasis cascade was primarily inhibited by NLGP, with no effect on metastasis-related invasion, migration, and extravasation. High infiltration of interferon γ (IFN-γ)–secreting cytotoxic CD8⁺ T cells [CD44⁺, CD69⁺, GranB⁺, IFN-γ⁺, and interleukin 2⁺] was documented in the metastatic site of NLGP-treated mice. Systemic CD8⁺ T cell depletion abolished NLGP-mediated metastasis inhibition and reappeared upon adoptive transfer of NLGP-activated CD8⁺ T cells. Interferon γ-secreting from CD8⁺ T cells inhibit the expression of angiogenesis regulatory vascular endothelial growth factor and transforming growth factor β and have an impact on the prevention of colonization. Neem leaf glycoprotein modulates dendritic cells (DCs) for proper antigen presentation by its DC surface binding and upregulation of MHC-I/II, CD86, and CCR7. Neem leaf glycoprotein–treated DCs specifically imprint CXCR3 and CCR4 homing receptors on activated CD8⁺ T cells, which helps to infiltrate into metastatic sites to restrain colonization. Such NLGP's effect on DCs is translation dependent and transcription independent. Studies using ovalbumin, OVA_257−264, and crude B16F10 antigen indicate MHC-I upregulation depends on the quantity of proteasome degradable peptide and only stimulates CD8⁺ T cells in the presence of antigen. Overall data suggest NLGP inhibits metastasis, in conjunction with tumor growth restriction, and thus might appear as a promising next-generation cancer immunotherapeutic.

NLGP counterbalances the immunosuppressive effect of tumor-associated mesenchymal stem cells to restore effector T cell functions

Background

A dynamic interaction between tumor cells and its surrounding stroma promotes the initiation, progression, metastasis, and chemoresistance of solid tumors. Emerging evidences suggest that targeting the stromal events could improve the efficacies of current therapeutics. Within tumor microenvironment (TME), stromal progenitor cells, i.e., MSCs, interact and eventually modulate the biology and functions of cancer and immune cells. Our recent finding disclosed a novel mechanism stating that tumor-associated MSCs inhibit the T cell proliferation and effector functions by blocking cysteine transport to T cells by dendritic cells (DCs), which makes MSCs as a compelling candidate as a therapeutic target. Immunomodulation by nontoxic neem leaf glycoprotein (NLGP) on dysfunctional cancer immunity offers significant therapeutic benefits to murine tumor host; however, its modulation on MSCs and its impact on T cell functions need to be elucidated.

Methods

Bone marrow-derived primary MSCs or murine 10 T1/2 MSCs were tumor-conditioned (TC-MSCs) and co-cultured with B16 melanoma antigen-specific DCs and MACS purified CD4⁺ and CD8⁺ T cells. T cell proliferation of T cells was checked by Ki67-based flow-cytometric and thymidine-incorporation assays. Cytokine secretion was measured by ELISA. The expression of cystathionase in DCs was assessed by RT-PCR. The STAT3/pSTAT3 levels in DCs were assessed by western blot, and STAT3 function was confirmed using specific SiRNA. Solid B16 melanoma tumor growth was monitored following adoptive transfer of conditioned CD8⁺ T cells.

Results

NLGP possesses an ability to restore anti-tumor T cell functions by modulating TC-MSCs. Supplementation of NLGP in DC-T cell co-culture significantly restored the inhibition in T cell proliferation and IFNγ secretion almost towards normal in the presence of TC-MSCs. Adoptive transfer of NLGP-treated TC-MSC supernatant educated CD8⁺ T cells in solid B16 melanoma bearing mice resulted in better tumor growth restriction than TC-MSC conditioned CD8⁺ T cells. NLGP downregulates IL-10 secretion by TC-MSCs, and concomitantly, pSTAT3 expression was downregulated in DCs in the presence of NLGP-treated TC-MSC supernatant. As pSTAT3 negatively regulates cystathionase expression in DCs, NLGP indirectly helps to maintain an almost normal level of cystathionase gene expression in DCs making them able to export sufficient amount of cysteine required for optimum T cell proliferation and effector functions within TME.

Conclusions

NLGP could be a prospective immunotherapeutic agent to control the functions and behavior of highly immunosuppressive TC-MSCs providing optimum CD8⁺ T cell functions to showcase an important new approach that might be effective in overall cancer treatment.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1349-z) contains supplementary material, which is available to authorized users.

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.