Extracellular Domain of IL-10 Receptor Chain-2 (IL-10R2) and Its Arginine-Containing Peptides Are Susceptible Substrates for Human Prostate Kallikrein-2 (KLK2).

The kallikrein-related peptidase KLK2 has restricted expression in the prostate luminal epithelium, and its protein target is unknown. The present work reports the hydrolytic activities of KLK2 on libraries of fluorescence resonance energy-transfer peptides from which the sequence SYRIF was the most susceptible substrate for KLK2. The sequence SYRIF is present at the extracellular N-terminal segment (58SYRIF63Q) of IL-10R2. KLK2 was fully active at pH 8.0-8.2, found only in prostate inflammatory conditions, and strongly activated by sodium citrate and glycosaminoglycans, the quantities and structures controlled by prostate cells. Bone-marrow-derived macrophages (BMDM) have IL-10R2 expressed on the cell surface, which is significantly reduced after KLK2 treatment, as determined by flow cytometry (FACS analysis). The IL-10 inhibition of the inflammatory response to LPS/IFN-γ in BMDM cells due to decreased nitric oxide, TNF-α, and IL-12 p40 levels is significantly reduced upon treatment of these cells with KLK2. Similar experiments with KLK3 did not show these effects. These observations indicate that KLK2 proteolytic activity plays a role in prostate inflammation and makes KLK2 a promising target for prostatitis treatment.

Antitumor effect of chiral organotelluranes elicited in a murine melanoma model.

Protease roles in cancer progression have been demonstrated and their inhibitors display antitumor effects. Cathepsins are lysosomal cysteine proteases that have increased expression in tumor cells, and tellurium compounds were described as potent cysteine protease inhibitors and also assayed in several animal models. In this work, the two enantiomeric forms of 1-[Butyl(dichloro)-λ4-tellanyl]-2-[1S-methoxyethyl]benzene (organotelluranes RF-13R and RF-13S) were evaluated as inhibitors of cathepsins B and L, showing significant enantiodiscrimination. We observed their cytotoxic effects on a murine melanoma model, effectively inhibiting tumor progression in vivo. The enantiomers were able to inhibit melanoma cell viability, migration and invasion in vitro. Besides, RF-13S and RF-13R were able to inhibit endothelial cell angiogenesis using a tube formation assay in vitro, in a stereodependent manner. These organotelluranes affected cell morphology, showing disassembling of the actin cytoskeleton. These results suggest organotelluranes as potential antitumor agents, acting directly on tumor cell proliferation, migration and invasion, and on endothelial cells, disrupting angiogenesis, showing low toxicity and high efficiency. Taken together our results suggest that this class of compounds should be further studied to reveal their potential as antitumoral agents.

Inhibition of melanoma metastasis by dual-peptide PLGA NPS.

Despite the positive results observed in vitro and in vivo, clinical trials with bioactive peptides are generally hampered by their fast degradation in the biological system. Two bioactive peptides, P20 (CSSRTMHHC) and the combined peptide C (CVNHPAFACGYGHTMYYHHYQHHL) have been identified as anticancer therapeutics. Combined peptide C consists of peptide C (CVNHPAFAC), a tumor-homing peptide, conjugated to the antiangiogenic peptide HTMYYHHYQHHL with a GYG. In this work, PLGA NPs with peptide C were applied as a dual-peptide carrier for application in cancer therapy. Peptide P20 was loaded into the NPs and combined peptide C was conjugated to the NPs surface. These NPs were evaluated as a therapeutic system to treat metastatic melanoma. In vivo assays showed that P20 encapsulation in PLGA NPs enhanced its antitumor activity. The inhibitory activity of P20-PLGANPs was similar to the activity of non-encapsulated P20 in a dose fivefold higher. The inhibitory activity was even higher when P20PLGA NPs were functionalized with combined peptide C. P20PLGAPepC NPs reduced in 28% the number of lung nodules in a syngeneic model of metastatic melanoma as compared to untreated animals. Additionally to the better tumor targeting and the in situ release of P20, it is expected that the therapeutic efficiency of the dual-peptide PLGA NPs was further enhanced by a synergistic effect between P20 and combined peptide C. Our encouraging results showed that by enabling the co-delivery of two peptides and promoting tumor targeting, PLGA NPs coupled with peptide C is a promising platform for peptide-based cancer therapy.

Camphene isolated from essential oil of Piper cernuum (Piperaceae) induces intrinsic apoptosis in melanoma cells and displays antitumor activity in vivo.

Natural monoterpenes were isolated from the essential oil of Piper cernuum Vell. (Piperaceae) leaves. The crude oil and the individual monoterpenes were tested for cytotoxicity in human tumor cell lineages and B16F10-Nex2 murine melanoma cells. In the present work we demonstrate the activity of camphene against different cancer cells, with its mechanism of action being investigated in vitro and in vivo in murine melanoma. Camphene induced apoptosis by the intrinsic pathway in melanoma cells mainly by causing endoplasmic reticulum (ER) stress, with release of Ca(2+) together with HmgB1 and calreticulin, loss of mitochondrial membrane potential and up regulation of caspase-3 activity. Importantly, camphene exerted antitumor activity in vivo by inhibiting subcutaneous tumor growth of highly aggressive melanoma cells in a syngeneic model, suggesting a promising role of this compound in cancer therapy.

Anti-metastatic immunotherapy based on mucosal administration of flagellin and immunomodulatory P10.

Current therapies against malignant melanoma generally fail to increase survival in most patients, and immunotherapy is a promising approach as it could reduce the dosage of toxic therapeutic drugs. In the present study, we show that an immunotherapeutic approach based on the use of the Toll-like receptor (TLR)-5 ligand flagellin (Salmonella Typhimurium FliCi) combined with the major histocompatibility complex class II-restricted P10 peptide, derived from the Paracoccidioides brasiliensis gp43 major surface protein, reduced the number of lung metastasis in a murine melanoma model. Compounds were administered intranasally into C57Bl/6 mice intravenously challenged with syngeneic B16F10-Nex2 melanoma cells, aiming at the local (pulmonary) immune response modulation. Along with a marked reduction in the number of lung nodules, a significant increase in survival was observed. The immunization regimen induced both local and systemic proinflammatory responses. Lung macrophages were polarized towards a M1 phenotype, lymph node cells, and splenocytes secreted higher interleukin-12p40 and interferon (IFN)-γ levels when re-stimulated with tumor antigens. The protective effect of the FliCi+P10 formulation required TLR-5, myeloid differentiation primary response gene 88 and IFN-γ expression, but caspase-1 knockout mice were only partially protected, suggesting that intracellular flagellin receptors are not involved with the anti-tumor effect. The immune therapy resulted in the activation of tumor-specific CD4(+) T lymphocytes, which conferred protection to metastatic melanoma growth after adoptive transfer. Taken together, our results report a new immunotherapeutic approach based on TLR-5 activation and IFN-γ production capable to control the metastatic growth of B16F10-Nex2 melanoma, being a promising alternative to be associated with chemotherapeutic drugs for an effective anti-tumor responses.

Radiochemical pharmacokinetic profile of P10 peptide with antifungal properties.

Paracoccidioidomycosis (PCM) is a chronic granulomatous disease that is caused by the thermally dimorphic fungus Paracoccidioides brasiliensis. It is endemic in some countries of Latin America and can cause a high-burden fungal infection with significant morbidity and mortality. The peptide P10, which demonstrates immune protection against experimental PCM, was radiolabeled with a radioisotope and evaluated in vivo. The radiolabeling was conducted to trace the pharmacokinetics of the molecule in principal organs and tissues. This was achieved with high radiochemical purity. Biodistribution and scintigraphic imaging showed fast blood clearance that was mainly renal; however, hepatobiliar excretion was also, with marked uptake in cervical lymph nodes. This profile may be useful for the development of a prophylactic drug or vaccine for patients exposed to PCM.

Immunization with P10 peptide increases specific immunity and protects immunosuppressed BALB/c mice infected with virulent yeasts of Paracoccidioides brasiliensis.

Paracoccidioidomycosis is a systemic granulomatous disease caused by Paracoccidioides spp. A peptide from the major diagnostic antigen gp43, named P10, induces a T-CD4(+) helper-1 immune response in mice and protects against intratracheal challenge with virulent P. brasiliensis. Previously, we evaluated the efficacy of the P10 peptide alone or combined with antifungal drugs in mice immunosuppressed and infected with virulent isolate of P. brasiliensis. In the present work, our data suggest that P10 immunization leads to an effective cellular immune response associated with an enhanced T cell proliferative response. P10-stimulated splenocytes increased nitric oxide (NO) production and induced high levels of IFN-γ, IL-1ß and IL-12. Furthermore, significantly increased concentrations of pro-inflammatory cytokines were also observed in lung homogenates of immunized mice. P10 immunization was followed by minimal fibrosis in response to infection. Combined with antifungal drugs, P10 immunization most significantly improved survival of anergic infected mice. Administration of either itraconazole or sulfamethoxazole/trimethoprim together with P10 immunization resulted in 100 % survival up to 200 days post-infection, whereas untreated mice died within 80 days. Hence, our data show that P10 immunization promotes a strong specific immune response even in immunocompromised hosts and thus P10 treatment represents a powerful adjuvant therapy to chemotherapy.

ß-Actin-binding complementarity-determining region 2 of variable heavy chain from monoclonal antibody C7 induces apoptosis in several human tumor cells and is protective against metastatic melanoma.

Complementarity-determining regions (CDRs) from monoclonal antibodies tested as synthetic peptides display anti-infective and antitumor activities, independent of the specificity of the native antibody. Previously, we have shown that the synthetic peptide C7H2, based on the heavy chain CDR 2 from monoclonal antibody C7, a mAb directed to a mannoprotein of Candida albicans, significantly reduced B16F10 melanoma growth and lung colony formation by triggering tumor apoptosis. The mechanism, however, by which C7H2 induced apoptosis in tumor cells remained unknown. Here, we demonstrate that C7H2 interacts with components of the tumor cells cytoskeleton, being rapidly internalized after binding to the tumor cell surface. Mass spectrometry analysis and in vitro validation revealed that ß-actin is the receptor of C7H2 in the tumor cells. C7H2 induces ß-actin polymerization and F-actin stabilization, linked with abundant generation of superoxide anions and apoptosis. Major phenotypes following peptide binding were chromatin condensation, DNA fragmentation, annexin V binding, lamin disruption, caspase 8 and 3 activation, and organelle alterations. Finally, we evaluated the cytotoxic efficacy of C7H2 in a panel of human tumor cell lines. All tumor cell lines studied were equally susceptible to C7H2 in vitro. The C7H2 amide without further derivatization significantly reduced lung metastasis of mice endovenously challenged with B16F10-Nex2 melanoma cells. No significant cytotoxicity was observed toward nontumorigenic cell lines on short incubation in vitro or in naïve mice injected with a high dose of the peptide. We believe that C7H2 is a promising peptide to be developed as an anticancer drug.

Chitin-like molecules associate with Cryptococcus neoformans glucuronoxylomannan to form a glycan complex with previously unknown properties.

In prior studies, we demonstrated that glucuronoxylomannan (GXM), the major capsular polysaccharide of the fungal pathogen Cryptococcus neoformans, interacts with chitin oligomers at the cell wall-capsule interface. The structural determinants regulating these carbohydrate-carbohydrate interactions, as well as the functions of these structures, have remained unknown. In this study, we demonstrate that glycan complexes composed of chitooligomers and GXM are formed during fungal growth and macrophage infection by C. neoformans. To investigate the required determinants for the assembly of chitin-GXM complexes, we developed a quantitative scanning electron microscopy-based method using different polysaccharide samples as inhibitors of the interaction of chitin with GXM. This assay revealed that chitin-GXM association involves noncovalent bonds and large GXM fibers and depends on the N-acetyl amino group of chitin. Carboxyl and O-acetyl groups of GXM are not required for polysaccharide-polysaccharide interactions. Glycan complex structures composed of cryptococcal GXM and chitin-derived oligomers were tested for their ability to induce pulmonary cytokines in mice. They were significantly more efficient than either GXM or chitin oligomers alone in inducing the production of lung interleukin 10 (IL-10), IL-17, and tumor necrosis factor alpha (TNF-α). These results indicate that association of chitin-derived structures with GXM through their N-acetyl amino groups generates glycan complexes with previously unknown properties.

Sialoglycoproteins in morphological distinct stages of Mucor polymorphosporus and their influence on phagocytosis by human blood phagocytes.

The possible role of sialic acids in host cells-fungi interaction and their association with glycoproteins were evaluated using a clinical isolate of the dimorphic fungus Mucor polymorphosporus. Lectin-binding assays with spores and yeast cells denoted the presence of surface sialoglycoconjugates containing 2,3- and 2,6-linked sialylglycosyl groups. Western blotting with peroxidase-labeled Limulus polyphemus agglutinin revealed the occurrence of different sialoglycoprotein types in both cell lysates and cell wall protein extracts of mycelia, spores, and yeasts of M. polymorphosporus. Sialic acids contributed to the surface negative charge of spores and yeast forms as evaluated by adherence to a cationic substrate. Sialidase-treated spores were less resistant to phagocytosis by human neutrophils and monocytes from healthy individuals than control (untreated) fungal suspensions. The results suggest that sialic acids are terminal units of various glycoproteins of M. polymorphosporus, contributing to negative charge of yeasts and spore cells and protecting infectious propagules from destruction by host cells.

Identification of a metallopeptidase with TOP-like activity in Paracoccidioides brasiliensis, with increased expression in a virulent strain.

Paracoccidioidomycosis (PCM), caused by the pathogenic fungus Paracoccidioides brasiliensis, is a systemic mycosis with severe acute and chronic forms. The pathology of PCM is not completely understood, and the role of proteases in the infection is not clearly defined. In this report, we describe a metallopeptidase activity in P. brasiliensis total and cytosolic protein extracts similar to that of mammalian thimet oligopeptidase (TOP). The analogous enzyme was suggested by analysis of P. brasiliensis genome databank and by hydrolytic activity of the FRET peptide Abz-GFSPFRQ-EDDnp which was completely inhibited by o-phenanthrolin and significantly inhibited by the TOP inhibitor, JA-2. This activity was also partially inhibited by IgG purified from patients with PCM, but not from normal individuals. As shown by high-performance liquid chromatography (HPLC), the hydrolysis of bradykinin had the same pattern as that of mammalian TOP, and anti-mammalian TOP antibodies significantly inhibited fungal cytosolic peptidase activity. Moreover, anti-mammalian TOP antibodies recognized a component of 80 kDa on fungal cytosol. A P. brasiliensis virulent isolate showed higher gene expression and TOP-like peptidase activity than a non-virulent strain. The release of enzyme following fungal lysis would be consistent with host antibody production and may have a role in the pathogenesis, inflammation and further development of the mycosis.

PLP2-derived peptide Rb4 triggers PARP-1-mediated necrotic death in murine melanoma cells.

Malignant melanoma is the main cause of death in patients with skin cancer. Overexpression of Proteolipid protein 2 (PLP2) increased tumor metastasis and the knockdown of PLP2 inhibited the growth and metastasis of melanoma cells. In the present work, we studied the antitumor activity of peptide Rb4 derived from protein PLP2. In vitro, Rb4 induced F-actin polymerization, prevented F-actin depolymerization and increased the ER-derived cytosolic calcium. Such effects were associated with necrosis of murine melanoma B16F10-Nex2 cells and with inhibition of the viability of human cancer cell lines. Loss of plasma membrane integrity, dilation of mitochondria, cytoplasm vacuolation and absence of chromatin condensation characterized tumor cell necrosis. Cleavage of PARP-1 and inhibition of RIP1 expression were also observed. In vivo, peptide Rb4 reduced the lung metastasis of tumor cells and delayed the subcutaneous melanoma growth in a syngeneic model. Rb4 induced the expression of two DAMPs molecules, HMGB1 and calreticulin, in B16F10-Nex2. Our results suggest that peptide Rb4 acts directly on tumor cells inducing the expression of DAMPs, which trigger the immunoprotective effect in vivo against melanoma cells. We suggest that peptide Rb4 is a promising compound to be developed as an anticancer drug.

The idiotype (Id) cascade in mice elicited the production of anti-R24 Id and anti-anti-Id monoclonal antibodies with antitumor and protective activity against human melanoma.

Gangliosides have been considered as potential targets for immunotherapy because they are overexpressed on the surface of melanoma cells. However, immunization with purified gangliosides results in a very poor immune response, usually mediated by IgM antibodies. To overcome this limitation, we immunized mice with R24, a monoclonal antibody (mAb) that recognizes the most tumor-restricted ganglioside (GD3); our goal was to obtain anti-idiotype (Id) antibodies bearing the internal image of GD3. Animals produced anti-Id and anti-anti-Id antibodies. Both anti-Id and anti-anti-Id antibodies were able to inhibit mAb R24 binding to GD3. In addition, the anti-anti-Id antibodies were shown to recognize GD3 directly. Anti-Id and anti-anti-Id mAb were then selected from two fusion experiments for evaluation. The most interesting finding emerged from the characterization of the anti-anti-Id mAb 5.G8. It was shown to recognize two different GD3-expressing human melanoma cell lines in vitro and to mediate tumor cell cytotoxicity by complement activation and antibody-dependent cellular cytotoxicity. The biological activity of the anti-anti-Id mAb was also tested in a mouse tumor model, in which it was shown to be a powerful growth inhibitor of melanoma cells. Thus, activity of the anti-anti-Id mAb 5.G8 matched that of the prototypic anti-GD3 mAb R24 both in vitro and in vivo. Altogether, our results indicate that the idiotype approach might produce high affinity, specific and very efficient antitumor immune responses.

α-Pinene isolated from Schinus terebinthifolius Raddi (Anacardiaceae) induces apoptosis and confers antimetastatic protection in a melanoma model.

Malignant melanoma is one the most aggressive types of cancer and its incidence has gradually increased in the last years, accounting for about 75% of skin cancer deaths. This poor prognosis results from the tumor resistance to conventional drugs mainly by deregulation of apoptotic pathways. The aim of this work was to investigate the cell death mechanism induced by α-pinene and its therapeutic application. Our results demonstrated that α-pinene was able to induce apoptosis evidenced by early disruption of the mitochondrial potential, production of reactive oxygen species, increase in caspase-3 activity, heterochromatin aggregation, DNA fragmentation and exposure of phosphatidyl serine on the cell surface. Most importantly, this molecule was very effective in the treatment of experimental metastatic melanoma reducing the number of lung tumor nodules. This is the first report on the apoptotic and antimetastatic activity of isolated α-pinene.

A cyclopalladated complex interacts with mitochondrial membrane thiol-groups and induces the apoptotic intrinsic pathway in murine and cisplatin-resistant human tumor cells.

BACKGROUND: Systemic therapy for cancer metastatic lesions is difficult and generally renders a poor clinical response. Structural analogs of cisplatin, the most widely used synthetic metal complexes, show toxic side-effects and tumor cell resistance. Recently, palladium complexes with increased stability are being investigated to circumvent these limitations, and a biphosphinic cyclopalladated complex {Pd(2) [S((-))C(2), N-dmpa](2) (µ-dppe)Cl(2)} named C7a efficiently controls the subcutaneous development of B16F10-Nex2 murine melanoma in syngeneic mice. Presently, we investigated the melanoma cell killing mechanism induced by C7a, and extended preclinical studies. METHODS: B16F10-Nex2 cells were treated in vitro with C7a in the presence/absence of DTT, and several parameters related to apoptosis induction were evaluated. Preclinical studies were performed, and mice were endovenously inoculated with B16F10-Nex2 cells, intraperitoneally treated with C7a, and lung metastatic nodules were counted. The cytotoxic effects and the respiratory metabolism were also determined in human tumor cell lines treated in vitro with C7a. RESULTS: Cyclopalladated complex interacts with thiol groups on the mitochondrial membrane proteins, causes dissipation of the mitochondrial membrane potential, and induces Bax translocation from the cytosol to mitochondria, colocalizing with a mitochondrial tracker. C7a also induced an increase in cytosolic calcium concentration, mainly from intracellular compartments, and a significant decrease in the ATP levels. Activation of effector caspases, chromatin condensation and DNA degradation, suggested that C7a activates the apoptotic intrinsic pathway in murine melanoma cells. In the preclinical studies, the C7a complex protected against murine metastatic melanoma and induced death in several human tumor cell lineages in vitro, including cisplatin-resistant ones. The mitochondria-dependent cell death was also induced by C7a in human tumor cells. CONCLUSIONS: The cyclopalladated C7a complex is an effective chemotherapeutic anticancer compound against primary and metastatic murine and human tumors, including cisplatin-resistant cells, inducing apoptotic cell death via the intrinsic pathway.

Intracellular Targeting of Poly Lactic-Co-Glycolic Acid Nanoparticles by Surface Functionalization with Peptides.

Nanoparticles (NPs) are a promising strategy for delivering drugs to specific sites because of their tunable size and surface chemistry variety. Among the availablematerials, NPs prepared with biopolymers are of particular interest because of their biocompatibility and controlled release of encapsulated drugs. Poly lactic-co-glycolic acid (PLGA) is one of the most widely used biopolymers in biomedical applications. In addition to material choice modulation of the interaction between NPs and biological systems is essential for the safety and effective use of NPs. Therefore, this work focused on evaluating different surface functionalization strategies to promote cancer cell uptake and intracellular targeting of PLGA NPs. Herein, cell-penetrating peptides (CPPs) were shown to successfully drive PLGA NPs to the mitochondria and nuclei. Furthermore, the functionalization of PLGA NPs with peptide AC-1001 H3 (GQYGNLWFAY) was proven to be useful for targeting actin filaments. The PLGA NPs cell internalization mechanism by B16F10-Nex2 cells was identified as caveolae-mediated endocytosis, which could be inhibited by the presence of methyl-ß-cyclodextrin. Notably, when peptide C (CVNHPAFAC) was used to functionalize PLGA NPs, none of the tested inhibitors could avoid cell internalization of PLGA NPs. Therefore, we suggest this peptide as a promising surface modification agent for enhancing drug delivery to cancer cells. Finally, PLGA NPs showed slow release kinetics and low cytotoxic profile, which, combined with the surface functionalization strategies addressed in this study, highlight the potential of PLGA NPs as a drug delivery platform for improving cancer therapy.

In vitro and in vivo trypanocidal effects of the cyclopalladated compound 7a, a drug candidate for treatment of Chagas' disease.

Chagas' disease, a neglected tropical infection, affects about 18 million people, and 100 million are at risk. The only drug available, benznidazole, is effective in the acute form and in the early chronic form, but its efficacy and tolerance are inversely related to the age of the patients. Side effects are frequent in elderly patients. The search for new drugs is thus warranted. In the present study we evaluated the in vitro and in vivo effect of a cyclopalladated compound (7a) against Trypanosoma cruzi, the agent of Chagas' disease. The 7a compound inhibits trypomastigote cell invasion, decreases intracellular amastigote proliferation, and is very effective as a trypanocidal drug in vivo, even at very low dosages. It was 340-fold more cytotoxic to parasites than to mammalian cells and was more effective than benznidazole in all in vitro and in vivo experiments. The 7a cyclopalladate complex exerts an apoptosis-like death in T. cruzi trypomastigote forms and causes mitochondrion disruption seen by electron microscopy.

Kinetic characterization of the Escherichia coli oligopeptidase A (OpdA) and the role of the Tyr(607) residue.

Oligopeptidase A (OpdA) belongs to the M3A subfamily of bacterial peptidases with catalytic and structural properties similar to mammalian thimet-oligopeptidase (TOP) and neurolysin (NEL). The three enzymes have four conserved Tyr residues on a flexible loop in close proximity to the catalytic site. In OpdA, the flexible loop is formed by residues 600-614 ((600)SHIFAGGYAAGYYSY(614)). Modeling studies indicated that in OpdA the Tyr(607) residue might be involved in the recognition of the substrate with a key role in catalysis. Two mutants were constructed replacing Tyr(607) by Phe (Y607F) or Ala (Y607A) and the influence of the site-directed mutagenesis in the catalytic process was examined. The hydrolysis of Abz-GXSPFRQ-EDDnp derivatives (Abz=ortho-aminobenzoic acid; EDDnp N-[2,4-dinitrophenyl]-ethylenediamine; X=different amino acids) was studied to compare the activities of wild-type OpdA (OpdA WT) and those of Y607F and Y607A mutants The results indicated that OpdA WT cleaved all the peptides only on the X-S bond whereas the Y607F and Y607A mutants were able to hydrolyze both the X-S and the P-F bonds. The kinetic parameters showed the importance of Tyr(607) in OpdA catalytic activity as its substitution promoted a decrease in the k(cat)/K(m) value of about 100-fold with Y607F mutant and 1000-fold with Y607A. Both mutations, however, did not affect protein folding as indicated by CD and intrinsic fluorescence analysis. Our results indicate that the OpdA Tyr(607) residue plays an important role in the enzyme-substrate interaction and in the hydrolytic activity.

Role for chitin and chitooligomers in the capsular architecture of Cryptococcus neoformans.

Molecules composed of beta-1,4-linked N-acetylglucosamine (GlcNAc) and deacetylated glucosamine units play key roles as surface constituents of the human pathogenic fungus Cryptococcus neoformans. GlcNAc is the monomeric unit of chitin and chitooligomers, which participate in the connection of capsular polysaccharides to the cryptococcal cell wall. In the present study, we evaluated the role of GlcNAc-containing structures in the assembly of the cryptococcal capsule. The in vivo expression of chitooligomers in C. neoformans varied depending on the infected tissue, as inferred from the differential reactivity of yeast forms to the wheat germ agglutinin (WGA) in infected brain and lungs of rats. Chromatographic and dynamic light-scattering analyses demonstrated that glucuronoxylomannan (GXM), the major cryptococcal capsular component, interacts with chitin and chitooligomers. When added to C. neoformans cultures, chitooligomers formed soluble complexes with GXM and interfered in capsular assembly, as manifested by aberrant capsules with defective connections with the cell wall and no reactivity with a monoclonal antibody to GXM. Cultivation of C. neoformans in the presence of an inhibitor of glucosamine 6-phosphate synthase resulted in altered expression of cell wall chitin. These cells formed capsules that were loosely connected to the cryptococcal wall and contained fibers with decreased diameters and altered monosaccharide composition. These results contribute to our understanding of the role played by chitin and chitooligosaccharides on the cryptococcal capsular structure, broadening the functional activities attributed to GlcNAc-containing structures in this biological system.

Therapies and Vaccines Based on Nanoparticles for the Treatment of Systemic Fungal Infections.

Treatment modalities for systemic mycoses are still limited. Currently, the main antifungal therapeutics include polyenes, azoles, and echinocandins. However, even in the setting of appropriate administration of antifungals, mortality rates remain unacceptably high. Moreover, antifungal therapy is expensive, treatment periods can range from weeks to years, and toxicity is also a serious concern. In recent years, the increased number of immunocompromised individuals has contributed to the high global incidence of systemic fungal infections. Given the high morbidity and mortality rates, the complexity of treatment strategies, drug toxicity, and the worldwide burden of disease, there is a need for new and efficient therapeutic means to combat invasive mycoses. One promising avenue that is actively being pursued is nanotechnology, to develop new antifungal therapies and efficient vaccines, since it allows for a targeted delivery of drugs and antigens, which can reduce toxicity and treatment costs. The goal of this review is to discuss studies using nanoparticles to develop new therapeutic options, including vaccination methods, to combat systemic mycoses caused by Candida sp., Cryptococcus sp., Paracoccidioides sp., Histoplasma sp., Coccidioides sp., and Aspergillus sp., in addition to providing important information on the use of different types of nanoparticles, nanocarriers and their corresponding mechanisms of action.