Successful Therapy of Murine Visceral Leishmaniasis with Astrakurkurone, a Triterpene Isolated from the Mushroom Astraeus hygrometricus, Involves the Induction of Protective Cell-Mediated Immunity and TLR9

Biological Properties, Health Benefits and Semisynthetic Derivatives of Edible Astraeus Mushrooms (Diplocystidiaceae): A Comprehensive Review

Edible Astraeus mushrooms are known for their nutritional and culinary benefits and potential therapeutic properties. However, more investigation and discussion are still needed to understand their mechanisms of action regarding observed biological activities and thorough chemical analysis of bioactive compounds. This review provides a comprehensive summary and discussion of the bioactive properties and mode of action of Astraeus extracts and their isolated compounds. It covers their reported antioxidant, anti-inflammatory, antidiabetic, anticancer, anti-tuberculosis, antimalarial, antiviral and antileishmanial activities, as well as their potential benefits on metabolic and cardiovascular health and immune function. The review highlights the significance of the biological potential of isolated compounds, such as sugar alcohols, polysaccharides, steroids, and lanostane triterpenoids. Moreover, the review identifies under-researched areas, such as the chemical analysis of Astraeus species, which holds immense research potential. Ultimately, the review aims to inspire further research on the nutraceuticals or therapeutics of these mushrooms.

An in-silico pharmacophore-based molecular docking study to evaluate the inhibitory potentials of novel fungal triterpenoid Astrakurkurone analogues against a hypothetical mutated main protease of SARS-CoV-2 virus

BACKGROUND

The main protease is an important structural protein of SARS-CoV-2, essential for its survivability inside a human host. Considering current vaccines' limitations and the absence of approved therapeutic targets, Mpro may be regarded as the potential candidate drug target. Novel fungal phytocompound Astrakurkurone may be studied as the potential Mpro inhibitor, considering its medicinal properties reported elsewhere.

METHODS

In silico molecular docking was performed with Astrakurkurone and its twenty pharmacophore-based analogues against the native Mpro protein. A hypothetical Mpro was also constructed with seven mutations and targeted by Astrakurkurone and its analogues. Furthermore, multiple parameters such as statistical analysis (Principal Component Analysis), pharmacophore alignment, and drug likeness evaluation were performed to understand the mechanism of protein-ligand molecular interaction. Finally, molecular dynamic simulation was done for the top-ranking ligands to validate the result.

RESULT

We identified twenty Astrakurkurone analogues through pharmacophore screening methodology. Among these twenty compounds, two analogues namely, ZINC89341287 and ZINC12128321 showed the highest inhibitory potentials against native and our hypothetical mutant Mpro, respectively (-7.7 and -7.3 kcal mol-1) when compared with the control drug Telaprevir (-5.9 and -6.0 kcal mol-1). Finally, we observed that functional groups of ligands namely two aromatic and one acceptor groups were responsible for the residual interaction with the target proteins. The molecular dynamic simulation further revealed that these compounds could make a stable complex with their respective protein targets in the near-native physiological condition.

CONCLUSION

To conclude, Astrakurkurone analogues ZINC89341287 and ZINC12128321 can be potential therapeutic agents against the highly infectious SARS-CoV-2 virus.

Traditional Uses, Phytochemical Composition, Pharmacological Properties, and the Biodiscovery Potential of the Genus Cirsium

Medicinal plants are rich in phytochemicals, which have been used as a source of raw material in medicine since ancient times. Presently they are mostly used to treat Henoch–Schonlein purpura, hemoptysis, and bleeding. The manuscript covers the classification, traditional applications, phytochemistry, pharmacology, herbal formulations, and patents of Cirsium. The main goal of this review is to impart recent information to facilitate future comprehensive research and use of Cirsium for the development of therapeutics. We investigated numerous databases PubMed, Google Scholar, Springer, Elsevier, Taylor and Francis imprints, and books on ethnopharmacology. The plants of the genus Cirsium of the family Asteraceae contain 350 species across the world. Phytochemical investigations showed that it contains flavonoids, phenols, polyacetylenes, and triterpenoids. The biological potential of this plant is contributed by these secondary metabolites. Cirsium plants are an excellent and harmless agent for the cure of liver diseases; therefore, they might be a good clinical option for the development of therapeutics for hepatic infections. The phytochemical studies of different Cirsium species and their renowned pharmacological activities could be exploited for pharmaceutic product development. Furthermore, studies are required on less known Cirsium species, particularly on the elucidation of the mode of action of their activities.

Host-directed antileishmanial interventions: Harvesting unripe fruits to reach fruition

Leishmaniasis is an exemplary paradigm of immune evasion, fraught with the perils of limited clinical assistance, escalating costs of treatment and made worse with the lack of suitable vaccine. While drugs remain central to large-scale disease control, the growing emergence of parasite resistance necessitates the need for combination therapy involving host-directed immunological agents. Also, since prolonged disease progression is associated with strong immune suppression of the host, augmentation of host immunity via restoration of the immunoregulatory circuit involving antigen-presenting cells and T-cells, activation of macrophage function and/or CD4⁺ T helper 1 cell differentiation may serve as an ideal approach to resolve severe cases of leishmaniasis. As such, therapies that embody a synergistic approach that involve direct killing of the parasite in addition to elevating host immunity are likely to pave the way for widespread elimination of leishmaniasis in the future. With this review, we aim to recapitulate the various immunotherapeutic agents found to hold promise in antileishmanial treatment both in vitro and in vivo. These include parasite-specific antigens, dendritic cell-targeted therapy, recombinant inhibitors of various components intrinsic to immune cell signaling and agonists or antagonists to immune cells and cytokines. We also summarize their abilities to direct therapeutic skewing of the host cell-immune response and review their potential to combat the disease either alone, or as adjunct modalities.

Evidence for Reversal of Immunosuppression by Homeopathic Medicine to a Predominant Th1-type Immune Response in BALB/c Mice Infected with Leishmania donovani

BACKGROUND

 Visceral leishmaniasis (VL) is a neglected tropical disease that is fatal if treatment is not given. The available chemotherapeutic options are unsatisfactory, and so complementary therapies like homeopathy might be a promising approach.

METHODS

 A nosode from a pure axenic culture of Leishmania donovani was prepared and screened for its anti-leishmanial potential both in an in-vitro and an in-vivo experimental approach.

RESULTS

 Leishmania donovani amastigote promastigote nosode (LdAPN 30C) exhibited significant anti-leishmanial activity against the promastigote forms of Leishmania donovani and was found to be safe. A study conducted on VL-infected mice revealed that LdAPN 30C resolved the disease by modulating the host immune response toward the Th1 type through upregulating the pro-inflammatory cytokines (IFN-γ and IL-17) and inducing nitric oxide (NO) levels in the infected macrophages. The hepatic parasite load was also found to be significantly decreased. The nosode was found to be safe, as no histological alterations in the liver or kidney were observed in the animals treated with the LdAPN 30C.

CONCLUSION

 This is the first study in which an axenic culture of Leishmania donovani has been used for the preparation of a homeopathic medication. The study highlights the anti-leishmanial and immunomodulatory potential of a homeopathic nosode in experimental VL.

Role of Cytokines in Experimental and Human Visceral Leishmaniasis

Visceral Leishmaniasis (VL) is the most fatal form of disease leishmaniasis. To date, there are no effective prophylactic measures and therapeutics available against VL. Recently, new immunotherapy-based approaches have been established for the management of VL. Cytokines, which are predominantly produced by helper T cells (Th) and macrophages, have received great attention that could be an effective immunotherapeutic approach for the treatment of human VL. Cytokines play a key role in forming the host immune response and in managing the formation of protective and non-protective immunities during infection. Furthermore, immune response mediated through different cytokines varies from different host or animal models. Various cytokines viz. IFN-γ, IL-2, IL-12, and TNF-α play an important role during protection, while some other cytokines viz. IL-10, IL-6, IL-17, TGF-β, and others are associated with disease progression. Therefore, comprehensive knowledge of cytokine response and their interaction with various immune cells is very crucial to determine appropriate immunotherapies for VL. Here, we have discussed the role of cytokines involved in VL disease progression or host protection in different animal models and humans that will determine the clinical outcome of VL and open the path for the development of rapid and accurate diagnostic tools as well as therapeutic interventions against VL.

Antiplasmodial and antileishmanial flavonoids from Mundulea sericea

Five known compounds (1-5) were isolated from the extract of Mundulea sericea leaves. Similar investigation of the roots of this plant afforded an additional three known compounds (6-8). The structures were elucidated using NMR spectroscopic and mass spectrometric analyses. The absolute configuration of 1 was established using ECD spectroscopy. In an antiplasmodial activity assay, compound 1 showed good activity with an IC₅₀ of 2.0 μM against chloroquine-resistant W2, and 6.6 μM against the chloroquine-sensitive 3D7 strains of Plasmodium falciparum. Some of the compounds were also tested for antileishmanial activity. Dehydrolupinifolinol (2) and sericetin (5) were active against drug-sensitive Leishmania donovani (MHOM/IN/83/AG83) with IC₅₀ values of 9.0 and 5.0 μM, respectively. In a cytotoxicity assay, lupinifolin (3) showed significant activity on BEAS-2B (IC₅₀ 4.9 μM) and HePG2 (IC₅₀ 10.8 μM) human cell lines. All the other compounds showed low cytotoxicity (IC₅₀ > 30 μM) against human lung adenocarcinoma cells (A549), human liver cancer cells (HepG2), lung/bronchus cells (epithelial virus transformed) (BEAS-2B) and immortal human hepatocytes (LO2).

A mushroom derived 'carbohydrate-fraction' reinstates host-immunity and protects from Leishmania donovani infection

The anti-leishmanial effect of the 'carbohydrate-fraction', isolated from an edible mushroom Astraeus hygrometricus, was evaluated against Leishmania donovani infection both in vitro and in vivo. Ah_f-Car induced the expression of inducible nitric oxide synthase 2 (iNOS2) and pro-inflammatory cytokines like TNF-α and IL-12, with subsequent downregulation of the anti-inflammatory cytokines as TGF-β and IL-10, in vitro and in vivo along with a remarkable increase in the expressions of IL-6, IL-1β, IFN-γ and IRFs, IRF-7 and IRF-8 in vivo. Ah_f-Car also reduced the parasite burden in the spleen and liver dose-dependently with a simultaneous proliferation of Ly6C⁺ cells in the bone marrow of Leishmania-infected experimental animals. It also increased the monocyte population dose-dependently and the expression of the myeloid transcription factor PU.1, in vivo, which presumably signifies the expansion of protective macrophages. Thus, Ah_f-Car might be a potent anti-leishmanial lead with unique and effective adjuvant capacity.

Combination of Mycobacterium indicus pranii and Heat-Induced Promastigotes Cures Drug-Resistant Leishmania Infection: Critical Role of Interleukin-6-Producing Classical Dendritic Cells

The major issues in available therapeutic modalities against leishmaniasis are cost, toxicity, and the emergence of drug resistance. The aim of this work was to develop a successful therapeutic adjuvant against drug-resistant Leishmania donovani infection by means of combining Mycobacterium indicus pranii with heat-induced promastigotes (HIP). One-month postinfected BALB/c mice were administered subcutaneously with M. indicus pranii (10⁸ cells) and HIP (100 μg) for 5 days. Spleens were harvested for flow cytometric and reverse transcriptase PCR analysis. The antileishmanial effect of the combination strategy was associated with induction of a disease-resolving Th1 and Th17 response with simultaneous downregulation of CD4⁺ CD25⁺ Foxp3⁺ (nTreg) cells and CD4⁺ CD25^- Foxp3^- (Tr1) cells in the spleen. The significant expansion of CD4⁺ T_CM (CD4⁺ CD44^hi CD11a^hi CD62L^hi) cells was a further interesting outcome of this therapeutic strategy in the context of long-term protection of hosts against secondary infection. Toll-like receptor 2 (TLR2) was also found instrumental in this antiparasitic therapy. Induced interleukin-6 (IL-6) production from expanded CD11c⁺ CD8α⁺ (cDC1) and CD11c⁺ CD11b⁺ (cDC2) dendritic cells (DCs) but not from the CD11b⁺ Ly6c⁺ inflammatory monocytes (iMOs), was found critical in the protective expansion of Th17 as evidenced by an in vivo IL-6 neutralization assay. It also promoted the hematopoietic conversion toward DC progenitors (pre-DCs) from common dendritic cell progenitors (CDPs), the immediate precursors, in bone marrow. This novel combinational strategy demonstrated that expansion of Th17 by IL-6 released from CD11c⁺ classical DCs is crucial, together with the conventional Th1 response, to control drug-resistant infection.

Mushrooms: an emerging resource for therapeutic terpenoids

Mankind has always been fascinated with nature and have heavily explored natural products since the ancient times. Evolution of diseases led to research on synthetic structure, specificity and activity-guided treatment. To combat threats of new developing diseases and the deleterious side effects posed by modern therapy, researchers have once again looked back towards natural resources. Although plants have been the main source of natural drugs, lower fungi are being recently paid attention to. Among them, mushrooms have emerged as an under-explored yet immensely rich resource, especially for bioactive terpenoids. A lot of research is going on around the world with mushroom-derived terpenoids especially their medicinal properties, some of which have even been used in pre- and post-clinical studies. From the literatures that are available, it was found that mushroom terpenoids have activity against a wide range of diseases. In this review, we have summarized different mushroom-derived terpenoids and their therapeutic properties.

Astrakurkurone, a sesquiterpenoid from wild edible mushroom, targets liver cancer cells by modulating Bcl-2 family proteins

Induction of apoptosis is the target of choice for modern chemotherapeutic treatment of cancer, where lack of potent "target-specific" drugs has led to extensive research on anticancer compounds from natural sources. In our study, we have used astrakurkurone, a triterpene isolated from wild edible mushroom, Astraeus hygrometricus. We have discussed the structure and stability of astrakurkurone employing single-crystal X-ray crystallography and studied its potential apoptogenicity in hepatocellular carcinoma (HCC) cells. Our experiments reveal that it is cytotoxic against the HCC cell lines (Hep 3B and Hep G2) at significantly low doses. Further investigations indicated that astrakurkurone acts by inducing apoptosis in the cells, disrupting mitochondrial membrane potential and inducing the expression of Bcl-2 family proteins, for example, Bax, and the downstream effector caspases 3 and 9. A molecular docking study also predicted direct interactions of the drug with antiapoptotic proteins Bcl-2 and Bcl-xL. Thus, astrakurkurone could become a valuable addition to the conventional repertoire of future anticancer drugs. © 2019 IUBMB Life, 1-11, 2019.

Lupeol induces immunity and protective efficacy in a murine model against visceral leishmaniasis

The available chemotherapeutics for the cure of visceral leishmaniasis (VL) are linked with many detrimental effects. Moreover, VL is associated with the suppression of protective Th1 immune response of the host and induction of disease exaggerating Th2 immune response. Therefore, there is an urgent requirement of therapeutics which can augment the immune status of the host to cure this disease. In the current investigation, the antileishmanial potential of lupeol was monitored in vitro and in vivo in inbred BALB/c mice against Leishmania donovani. Lupeol showed potent antipromastigote activity via arresting parasites at sub G0/G1 phase in vitro. Lupeol significantly decreased the splenic parasite burden by inducing strong delayed-type hypersensitivity responses in contrary to untreated infected animals. The therapeutic efficacy of lupeol was observed to be similar to the reference drug, AmB. Treatment of infected animals with lupeol depicted enhanced levels of T cells and Th1 cytokines in contrast to only infected controls. Further lupeol treatment upregulated the levels of nuclear factor κ B and nitric oxide synthase genes and elevated the production of reactive oxygen species and nitric oxide. Unlike AmB, lupeol-treated infected animals did not show any toxicity. These findings are promising and indicate that lupeol can serve as a prototype drug for the cure of VL.

Cytokines: Key Determinants of Resistance or Disease Progression in Visceral Leishmaniasis: Opportunities for Novel Diagnostics and Immunotherapy

Leishmaniasis is a parasitic disease of humans, highly prevalent in parts of the tropics, subtropics, and southern Europe. The disease mainly occurs in three different clinical forms namely cutaneous, mucocutaneous, and visceral leishmaniasis (VL). The VL affects several internal organs and is the deadliest form of the disease. Epidemiology and clinical manifestations of VL are variable based on the vector, parasite (e.g., species, strains, and antigen diversity), host (e.g., genetic background, nutrition, diversity in antigen presentation and immunity) and the environment (e.g., temperature, humidity, and hygiene). Chemotherapy of VL is limited to a few drugs which is expensive and associated with profound toxicity, and could become ineffective due to the parasites developing resistance. Till date, there are no licensed vaccines for humans against leishmaniasis. Recently, immunotherapy has become an attractive strategy as it is cost-effective, causes limited side-effects and do not suffer from the downside of pathogens developing resistance. Among various immunotherapeutic approaches, cytokines (produced by helper T-lymphocytes) based immunotherapy has received great attention especially for drug refractive cases of human VL. Therefore, a comprehensive knowledge on the molecular interactions of immune cells or components and on cytokines interplay in the host defense or pathogenesis is important to determine appropriate immunotherapies for leishmaniasis. Here, we summarized the current understanding of a wide-spectrum of cytokines and their interaction with immune cells that determine the clinical outcome of leishmaniasis. We have also highlighted opportunities for the development of novel diagnostics and intervention therapies for VL.

Live Attenuated Leishmania donovani Centrin Gene-Deleted Parasites Induce IL-23-Dependent IL-17-Protective Immune Response against Visceral Leishmaniasis in a Murine Model

No vaccine exists against visceral leishmaniasis. To develop effective vaccines, we have previously reported protective role of live attenuated centrin gene-deleted Leishmania donovani (LdCen^-/- ) parasites through induction of Th1 type immune response in mice, hamsters, and dogs. In this study, we specifically explored the role of Th17 cells in LdCen^-/- -induced host protection in mice. Our results showed that compared with wild-type L. donovani infection, LdCen^-/- parasites induce significantly higher expression of Th17 differentiation cytokines in splenic dendritic cells. There was also induction of IL-17 and its promoting cytokines in total splenocytes and in both CD4 and CD8 T cells following immunization with LdCen^-/- Upon challenge with wild-type parasites, IL-17 and its differentiating cytokines were significantly higher in LdCen^-/- -immunized mice compared with nonimmunized mice that resulted in parasite control. Alongside IL-17 induction, we observed induction of IFN-γ-producing Th1 cells as reported earlier. However, Th17 cells are generated before Th1 cells. Neutralization of either IL-17 or IFN-γ abrogated LdCen^-/- -induced host protection further confirming the essential role of Th17 along with Th1 cytokines in host protection. Treatment with recombinant IL-23, which is required for stabilization and maintenance of IL-17, heightened Th17, and Tc17 responses in immunized mice splenocytes. In contrast, Th17 response was absent in immunized IL-23R^-/- mice that failed to induce protection upon virulent Leishmania challenge suggesting that IL-23 plays an essential role in IL-17-mediated protection by LdCen^-/- parasites. This study unveiled the role of IL-23-dependent IL-17 induction in LdCen^-/- parasite-induced immunity and subsequent protection against visceral leishmaniasis.

Therapeutic effect of ursolic acid in experimental visceral leishmaniasis

Leishmaniasis is an important neglected tropical disease, affecting more than 12 million people worldwide. The available treatments are not well tolerated and present diverse side effects in patients, justifying the search for new therapeutic compounds. In the present study, the therapeutic potential and toxicity of ursolic acid (UA), isolated from the leaves of Baccharis uncinella C. DC. (Asteraceae), were evaluated in experimental visceral leishmaniasis. To evaluate the therapeutic potential of UA, hamsters infected with L. (L.) infantum were treated daily during 15 days with 1.0 or 2.0 mg UA/kg body weight, or with 5.0 mg amphotericin B/kg body weight by intraperitoneal route. Fifteen days after the last dose, the parasitism of the spleen and liver was stimated and the main histopathological alterations were recorded. The proliferation of splenic mononuclear cells was evaluated and IFN-γ, IL-4, and IL-10 gene expressions were analyzed in spleen fragments. The toxicity of UA and amphotericin B were evaluated in healthy golden hamsters by histological analysis and biochemical parameters. Animals treated with UA had less parasites in the spleen and liver when compared with the infected control group, and they also showed preservation of white and red pulps, which correlate with a high rate of proliferation of splenic mononuclear cells, IFN-γ mRNA and iNOS production. Moreover, animals treated with UA did not present alterations in the levels of AST, ALT, creatinine and urea. Taken together, these findings indicate that UA is an interesting natural compound that should be considered for the development of prototype drugs against visceral leishmaniasis.

Antileishmanial ferrocenylquinoline derivatives: Synthesis and biological evaluation against Leishmania donovani

The emergence of resistance against existing antileishmanial drugs necessitates the search for new classes of antileishmanial compounds. Herein a series of structurally diverse ferrocenylquinolines have been synthesized and evaluated for in vitro antileishmanial activity against Leishmania donovani using the MTT assay. Thirteen (M2-M14) substituted ferrocenylquinoline congeners possessing triazole rings were generated by palladium mediated Suzuki-Miyaura coupling reaction of 5-iodoferrocenylquinolinetriazole and substituted arylboronic acids. All the synthesized compounds were tested for its antileishmanial activity using both promastigote and amastigote stages of L. donovani. Among them, three compounds (M4, M7 and M9) exhibited promising anti-promastigote activity, with an IC₅₀ value of 28.7 μM, 22.1 μM and 28 μM, respectively, and no cytotoxicity toward host splenocytes. These three compounds are equally effective against the intracellular amastigote stage of L. donovani showing the IC₅₀ values of 16 μM (M4), 8 μM (M7) and 16 μM (M9), respectively, with consistent nitric oxide generation as required for parasite clearance. From the battery of tests conducted in this study, it appears that these compounds induce parasite death by promoting cell cycle arrest and triggering apoptosis.

Role of pro-inflammatory cytokine IL-17 in Leishmania pathogenesis and in protective immunity by Leishmania vaccines

The clinical outcome of Leishmania pathogenesis ranges from active skin lesions to fatal visceral dissemination and severely impaired T cell immunity. It is well established that a strong Th1 immune response is protective against cutaneous forms of the disease, however a mixed Th1/Th2 response is most commonly observed against visceral infections as evident from previous studies. Aside from Th1/Th2 cytokines, the pro-inflammatory IL-17 cytokine family plays an important role in the clearance of intracellular pathogens. In Leishmania induced skin lesions, IL-17 produced by Th17 cells is shown to exacerbate the disease, suggesting a role in pathogenesis. However, a protective role for IL-17 is indicated by the expansion of IL-17 producing cells in vaccine-induced immunity. In human visceral leishmaniasis (VL) it has been demonstrated that IL-17 and IL-22 are associated with protection against re-exposure to Leishmania, which further suggests the involvement of IL-17 in vaccine induced protective immunity. Although there is no vaccine against any form of leishmaniasis, the development of genetically modified live attenuated parasites as vaccine candidates prove to be promising, as they successfully induce a robust protective immune response in various animal models. However, the role of IL-17 producing cells and Th17 cells in response to these vaccine candidates remains unexplored. In this article, we review the role of IL-17 in Leishmania pathogenesis and the potential impact on vaccine induced immunity, with a special focus on live attenuated Leishmania parasites.