Inhibitors to degraders: Changing paradigm in drug discovery.

The chemical understanding of biological processes provides not only a deeper insight but also a solution to abnormal biological functioning. Protein degradation, a natural biological process for debris removal in the cell, has been studied for years. The recent finding that natural degradation pathways can be utilized for therapeutic purposes is a paradigm shift in the drug discovery approach. Methods such as Proteolysis Targeting Chimera (PROTAC), lysosomal targeting chimera, hydrophobic tagging, AUtophagy TArgeting Chimera, AUTOphagy TArgeting Chimera and several other variants of these methods have made a considerable impact on the way of drug design. Few selected examples testify that a huge wave of change is on the way. The drug design based on the targeted protein degradation is a powerful tool in our arsenal. More molecules will be invented that will uncover the hidden secrets of biological functioning and provide enduring solutions to several unmet medical needs.

Tackling the emerging Artemisinin-resistant malaria parasite by modulation of defensive oxido-reductive mechanism via nitrofurantoin repurposing.

Oxidative stress-mediated cell death has remained the prime parasiticidal mechanism of front line antimalarial, artemisinin (ART). The emergence of resistant Plasmodium parasites characterized by oxidative stress management due to impaired activation of ART and enhanced reactive oxygen species (ROS) detoxification has decreased its clinical efficacy. This gap can be filled by development of alternative chemotherapeutic agents to combat resistance defense mechanism. Interestingly, repositioning of clinically approved drugs presents an emerging approach for expediting antimalarial drug development and circumventing resistance. Herein, we evaluated the antimalarial potential of nitrofurantoin (NTF), a clinically used antibacterial drug, against intra-erythrocytic stages of ART-sensitive (Pf3D7) and resistant (PfKelch13R539T) strains of P. falciparum, alone and in combination with ART. NTF exhibited growth inhibitory effect at submicro-molar concentration by arresting parasite growth at trophozoite stage. It also inhibited the survival of resistant parasites as revealed by ring survival assay. Concomitantly, in vitro combination assay revealed synergistic association of NTF with ART. NTF was found to enhance the reactive oxygen and nitrogen species, and induced mitochondrial membrane depolarization in parasite. Furthermore, we found that exposure of parasites to NTF disrupted redox balance by impeding Glutathione Reductase activity, which manifests in enhanced oxidative stress, inducing parasite death. In vivo administration of NTF, alone and in combination with ART, in P. berghei ANKA-infected mice blocked parasite multiplication and enhanced mean survival time. Overall, our results indicate NTF as a promising repurposable drug with therapeutic potential against ART-sensitive as well as resistant parasites.

A C2 domain containing plasma membrane protein of Plasmodium falciparum merozoites mediates calcium-dependent binding and invasion to host erythrocytes.

BACKGROUND: Invasion of red blood cells by Plasmodium falciparum merozoites is governed by multiple receptor-ligand interactions which are critical for bridging the two cells together. The critical function of these ligands for invasion and their direct exposure to the host immune system makes them lucrative vaccine candidates. This necessitates the discovery of new adhesins with less redundancy that mediates the binding of merozoite to the red cell, and furthermore invasion into it. Here we have identified a novel membrane associated antigen (PfC2DMA) that is conserved throughout the Plasmodium species and has a membrane targeting C2 domain at its extreme N-terminal region. METHODS: Recombinant C2dom was expressed heterologously in bacteria and purified to homogeneity. Mice antisera against C2dom was raised and used to check the expression and intraparasitic localization of the protein. RBC and Ca2+ ion binding activity of C2dom was also checked. RESULTS: C2dom exhibited specific binding to Ca2+ ions and not to Mg2+ ions. PfC2DMA localized to the surface of merozoite and recombinant C2dom bound to the surface of human RBCs. RBC receptor modification by treatment with different enzymes showed that binding of C2dom to RBC surface is neuraminidase sensitive. Mice antisera raised against C2dom of Pf C2DMA showed invasion inhibitory effects. CONCLUSION: Our findings suggest that C2dom of PfC2DMA binds to surface of red cell in a Ca2+-dependent manner, advocating a plausible role in invasion and can serve as a potential novel blood stage vaccine candidate.

Prefoldin subunit 6 of Plasmodium falciparum binds merozoite surface protein-1.

Malaria is a human disease caused by eukaryotic protozoan parasites of the Plasmodium genus. Plasmodium falciparum (Pf) causes the most lethal form of human malaria and is responsible for widespread mortality worldwide. Prefoldin is a heterohexameric molecular complex that binds and delivers unfolded proteins to chaperonin for correct folding. The prefoldin PFD6 is predicted to interact with merozoite surface protein-1 (MSP-1), a protein well known to play a pivotal role in erythrocyte binding and invasion by Plasmodium merozoites. We previously found that the P. falciparum (Pf) genome contains six prefoldin genes and a prefoldin-like gene whose molecular functions are unidentified. Here, we analyzed the expression of PfPFD-6 during the asexual blood stages of the parasite and investigated its interacting partners. PfPFD-6 was found to be significantly expressed at the trophozoite and schizont stages. Pull-down assays suggest PfPFD-6 interacts with MSP-1. In silico analysis suggested critical residues involved in the PfPFD-6-MSP-1 interaction. Our data suggest PfPFD-6 may play a role in stabilizing or trafficking MSP-1.

A Fast-Track Phenotypic Characterization of Plasmodium falciparum Vaccine Antigens through Lyse-Reseal Erythrocytes Mediated Delivery (LyRED) of RNA Interference for Targeted Translational Repression.

The minimal success of the malaria vaccine with available antigens indicates the need for intensive and accelerated research to identify and characterize new antigens that confer protection against infection, clinical manifestation, and even malaria transmission. Further, the genetic manipulation tools to characterize such antigens are very time-consuming and laborious due to the very low efficiency of transfection in the malaria parasite. Here, we report a human miRNA-mediated translational repression of antigens in Plasmodium falciparum as a fast-track method for understanding and validating their function. In this method, candidate miRNAs are designed based on favorable hybridization energy against a parasite gene, and miRNA mimics are delivered to the parasite by loading them as cargo in the erythrocytes by simple lyse-reseal method. Incubation of the miRNA loaded erythrocytes with purified mature trophozoites or schizonts results in the loaded erythrocytes' infection. The miRNA mimics are translocated to parasites, and the effect of miRNA-mediated translation repression can be monitored within 48-72 h post-invasion. Unlike other transfection based methods, this method is fast, reproducible, and robust. We call this method as lyse-reseal erythrocytes for delivery (LyRED) of miRNA, which is a rapid and straight-forward method providing an efficient alternative to the existing genetic tools for P. falciparum to characterize the function of antigens or genes. The identification of crucial antigens from the different stages of the Plasmodium falciparum life cycle by the miRNA targeting approach can fuel the development of efficacious subunit vaccines against malaria.

Interaction of Plasmodium falciparum apicortin with α- and ß-tubulin is critical for parasite growth and survival.

Cytoskeletal structures of Apicomplexan parasites are important for parasite replication, motility, invasion to the host cell and survival. Apicortin, an Apicomplexan specific protein appears to be a crucial factor in maintaining stability of the parasite cytoskeletal assemblies. However, the function of apicortin, in terms of interaction with microtubules still remains elusive. Herein, we have attempted to elucidate the function of Plasmodium falciparum apicortin by monitoring its interaction with two main components of parasite microtubular structure, α-tubulin-I and ß-tubulin through in silico and in vitro studies. Further, a p25 domain binding generic drug Tamoxifen (TMX), was used to disrupt PfApicortin-tubulin interactions which led to the inhibition in growth and progression of blood stage life cycle of P. falciparum.

Pathogen induced subversion of NAD+ metabolism mediating host cell death: a target for development of chemotherapeutics.

Hijacking of host metabolic status by a pathogen for its regulated dissemination from the host is prerequisite for the propagation of infection. M. tuberculosis secretes an NAD+-glycohydrolase, TNT, to induce host necroptosis by hydrolyzing Nicotinamide adenine dinucleotide (NAD+). Herein, we expressed TNT in macrophages and erythrocytes; the host cells for M. tuberculosis and the malaria parasite respectively, and found that it reduced the NAD+ levels and thereby induced necroptosis and eryptosis resulting in premature dissemination of pathogen. Targeting TNT in M. tuberculosis or induced eryptosis in malaria parasite interferes with pathogen dissemination and reduction in the propagation of infection. Building upon our discovery that inhibition of pathogen-mediated host NAD+ modulation is a way forward for regulation of infection, we synthesized and screened some novel compounds that showed inhibition of NAD+-glycohydrolase activity and pathogen infection in the nanomolar range. Overall this study highlights the fundamental importance of pathogen-mediated modulation of host NAD+ homeostasis for its infection propagation and novel inhibitors as leads for host-targeted therapeutics.

Chorismate synthase mediates cerebral malaria pathogenesis by eliciting salicylic acid-dependent autophagy response in parasite.

Cerebral malaria caused by Plasmodium falciparum is the severest form of the disease resulting in the morbidity of a huge number of people worldwide. Development of effective curatives is essential in order to overcome the fatality of cerebral malaria. Earlier studies have shown the presence of salicylic acid (SA) in malaria parasite P. falciparum, which plays a critical role in the manifestation of cerebral malaria. Further, the application of SA for the treatment of acute symptoms in cerebral malaria increases the activity of iNOS leading to severe inflammation-mediated death, also called as Reye's syndrome. Therefore, modulation of the level of SA might be a novel approach to neutralize the symptoms of cerebral malaria. The probable source of parasite SA is the shikimate pathway, which produces chorismate, a precursor to aromatic amino acids and other secondary metabolites like SA in the parasite. In this work, we performed the immunological, pathological and biochemical studies in mice infected with chorismate synthase knocked-out Plasmodium berghei ANKA, which does not produce SA. Fewer cerebral outcomes were observed as compared to the mice infected with wild-type parasite. The possible mechanism behind this protective effect might be the hindrance of SA-mediated induction of autophagy in the parasite, which helps in its survival in the stressed condition of brain microvasculature during cerebral malaria. The absence of SA leading to reduced parasite load along with the reduced pathological symptoms contributes to less fatality outcome by cerebral malaria.

A study on the change in HbA1c levels before and after non-surgical periodontal therapy in type-2 diabetes mellitus in generalized periodontitis.

AIM: The aim of this study was to evaluate and investigate changes in HbA1c levels before and after non-surgical periodontal therapy in type-2 diabetes mellitus patients with generalized periodontitis. MATERIALS AND METHODS: A statistically significant number of type-2 diabetes mellitus subjects diagnosed with chronic generalized periodontitis were included in the study. The selected subjects were randomly allocated to 2 groups. Group 1: Control group: Subjects who received only scaling and root planning. Group 2: Test group: Subjects received antibiotic coverage with non-surgical periodontal therapy (scaling and root planning). Clinical parameters included plaque index, gingival index, PRO MIG pocket depth, and clinical attachment level. In addition, the metabolic parameters were recorded at the same time intervals, which included fasting blood sugar, random blood sugar, and HbA1c levels. STATISTICAL ANALYSIS: ANOVA test was applied to the parameters. RESULTS: HbA1c more significantly reduced by test group compared to the other group. Conclusion: there is definitely a positive effect of nonsurgical on HbA1c levels in type 2 diabetes mellitus. This point levels significantly reduced after conventional non-surgical periodontal therapy. CONCLUSION: There is definitely a positive effect of non-surgical periodontal therapy on HbA1c levels in type 2 diabetes patients with chronic periodontitis.

First Degree Relatives of Patients with Celiac Disease Harbour an Intestinal Transcriptomic Signature that Might Protect them from Enterocyte Damage.

INTRODUCTION: Celiac disease (CeD) is an autoimmune enteropathy which affects approximately 0.7% of the global population. While first-degree relatives (FDR) of patients with CeD have a 7.5% risk of developing enteropathy, many remain protected. Therefore, intestinal mucosa of FDR might have protective compensatory mechanisms against immunological injury. We have explored the protective mechanisms that may be active in intestinal mucosa of FDR. METHODS: Intestinal mucosal biopsies (4-5 pieces) from treatment naïve patients with CeD (n = 12), FDR (n = 12) (anti-tTG negative) and controls (n = 12) (anti-tTG negative) were obtained from each individual and subjected to microarray analysis using HT-12-v4 Human Expression BeadChips (Illumina). Differential gene expression analysis was carried out among CeD, FDR and controls; and resulting gene lists were analyzed using gene ontology and pathway enrichment tools. RESULTS: Patients with CeD, FDR and control groups displayed significant differential gene expression. Thirty seven genes were upregulated and 372 were downregulated in the intestinal mucosa of FDR in comparison to CeD and controls. Pseudogenes constituted about 18% (315/1751) of FDR differentially expressed genes, and formed "clusters" that associated uniquely with individual study groups. The three study groups segregated into distinct clusters in unsupervised (PCA) and supervised (random forests) modelling approaches. Pathways analysis revealed an emphasis on crypt-villous maintenance and immune regulation in the intestinal mucosa of FDR. CONCLUSIONS: Our analysis suggests that the intestinal mucosa of celiac FDR consist of a unique molecular phenotype that is distinct from CeD and controls. The transcriptomic landscape of FDR promotes maintenance of crypt-villous axis and modulation of immune mechanisms. These differences clearly demonstrate the existence of compensatory protective mechanisms in the FDR intestinal mucosa.

Host-Parasite Interactions in Human Malaria: Clinical Implications of Basic Research.

The malaria parasite, Plasmodium, is one of the oldest parasites documented to infect humans and has proven particularly hard to eradicate. One of the major hurdles in designing an effective subunit vaccine against the malaria parasite is the insufficient understanding of host-parasite interactions within the human host during infections. The success of the parasite lies in its ability to evade the human immune system and recruit host responses as physiological cues to regulate its life cycle, leading to rapid acclimatization of the parasite to its immediate host environment. Hence understanding the environmental niche of the parasite is crucial in developing strategies to combat this deadly infectious disease. It has been increasingly recognized that interactions between parasite proteins and host factors are essential to establishing infection and virulence at every stage of the parasite life cycle. This review reassesses all of these interactions and discusses their clinical importance in designing therapeutic approaches such as design of novel vaccines. The interactions have been followed from the initial stages of introduction of the parasite under the human dermis until asexual and sexual blood stages which are essential for transmission of malaria. We further classify the interactions as "direct" or "indirect" depending upon their demonstrated ability to mediate direct physical interactions of the parasite with host factors or their indirect manipulation of the host immune system since both forms of interactions are known to have a crucial role during infections. We also discuss the many ways in which this understanding has been taken to the field and the success of these strategies in controlling human malaria.

Evaluation of specifically designed implants placed in the low-density jaw bones: A clinico-radiographical study.

AIM: In the less dense bone, it is difficult to obtain implant anchorage. The present study was undertaken to determine the survival rate of Maestro™ implants placed in d3 and d4 bones. MATERIALS AND METHODS: Fourteen patients (10 males and 4 females) were selected for the study and implants were evaluated for posttreatment changes in at 3, 6, 9 and 12 months from implant placement. The implant probing depth and mobility were recorded 3 and 6 months after prosthesis placement. Also, peri-implant bone level was assessed at the baseline and 12 months postoperatively, followed by a statistical analysis. RESULTS: The mean plaque and gingival indices showed a reduction at repeated intervals. The mean sulcular bleeding showed a slight reduction which was statistically significant. An overall mean bone loss was observed after 12 months follow-up, which was statistically not significant. The overall survival rate of implants was reported as 92.3%. CONCLUSION: The specific implant used in the study is advantageous in the soft bone condition. CLINICAL SIGNIFICANCE: Although, there is a great evidence of implant failure in compromised jaw quality, the newer designs and approaches suggest that the poor quality is not a contraindication.