Cu(II) binding to the λ6aJL2-R24G antibody light chain protein associated with light chain amyloidosis disease: The role of histidines.

Light chain amyloidosis is a conformational disease caused by the abnormal proliferation and deposition of antibody light chains as amyloid fibers in organs and tissues. The effect of Cu(II) binding to the model recombinant protein 6aJL2-R24G was previously characterized in our group, and we found an acceleration of the aggregation kinetics of the protein. In this study, in order to confirm the Cu(II) binding sites, histidine variants of 6aJL2-R24G were prepared and the effects of their interaction with Cu(II) was analyzed by circular dichroism, fluorescence spectroscopy, isothermal calorimetry titrations, and molecular dynamics simulations. Confirming our earlier work, we found that His8 and His99 are the highest affinity Cu(II) binding sites, and that Cu(II) binding to both sites is a cooperative event.

Ligand-Based Drug Design of Genipin Derivatives with Cytotoxic Activity against HeLa Cell Line: A Structural and Theoretical Study.

Cervical cancer is a malignant neoplastic disease, mainly associated to HPV infection, with high mortality rates. Among natural products, iridoids have shown different biological activities, including cytotoxic and antitumor effects, in different cancer cell types. Geniposide and its aglycone Genipin have been assessed against different types of cancer. In this work, both iridoids were evaluated against HeLa and three different cervical cancer cell lines. Furthermore, we performed a SAR analysis incorporating 13 iridoids with a high structural similarity to Geniposide and Genipin, also tested in the HeLa cell line and at the same treatment time. Derived from this analysis, we found that the dipole moment (magnitude and direction) is key for their cytotoxic activity in the HeLa cell line. Then, we proceeded to the ligand-based design of new Genipin derivatives through a QSAR model (R2 = 87.95 and Q2 = 62.33) that incorporates different quantum mechanic molecular descriptor types (ρ, ΔPSA, ∆Polarizability2, and logS). Derived from the ligand-based design, we observed that the presence of an aldehyde or a hydroxymethyl in C4, hydroxyls in C1, C6, and C8, and the lack of the double bond in C7-C8 increased the predicted biological activity of the iridoids. Finally, ten simple iridoids (D9, D107, D35, D36, D55, D56, D58, D60, D61, and D62) are proposed as potential cytotoxic agents against the HeLa cell line based on their predicted IC50 value and electrostatic features.

Tannic Acid and Ethyl Gallate Potentialize Paclitaxel Effect on Microtubule Dynamics in Hep3B Cells.

Among broad-spectrum anticancer agents, paclitaxel (PTX) has proven to be one of the most effective against solid tumors for which more specific treatments are lacking. However, drawbacks such as neurotoxicity and the development of resistance reduce its therapeutic efficacy. Therefore, there is a need for compounds able to improve its activity by synergizing with it or potentiating its effect, thus reducing the doses required. We investigated the interaction between PTX and tannins, other compounds with anticancer activity known to act as repressors of several proteins involved in oncological pathways. We found that both tannic acid (TA) and ethyl gallate (EG) strongly potentiate the toxicity of PTX in Hep3B cells, suggesting their utility in combination therapy. We also found that AT and EG promote tubulin polymerization and enhance the effect of PTX on tubulin, suggesting a direct interaction with tubulin. Biochemical experiments confirmed that TA, but not EG, binds tubulin and potentiates the apparent binding affinity of PTX for the tubulin binding site. Furthermore, the molecular docking of TA to tubulin suggests that TA can bind to two different sites on tubulin, one at the PTX site and the second at the interface of α and ß-tubulin (cluster 2). The binding of TA to cluster 2 could explain the overstabilization in the tubulin + PTX combinatorial assay. Finally, we found that EG can inhibit PTX-induced expression of pAkt and pERK defensive protein kinases, which are involved in resistance to PXT, by limiting cell death (apoptosis) and favoring cell proliferation and cell cycle progression. Our results support that tannic acid and ethyl gallate are potential chemotherapeutic agents due to their potentiating effect on paclitaxel.

Quartz Crystal Microbalance Application and In Silico Studies to Characterize the Interaction of Bovine Serum Albumin with Plasma Polymerized Pyrrole Surfaces: Implications for the Development of Biomaterials.

Plasma polymerized pyrrole/iodine (PPPy/I) microparticles and bovine serum albumin (BSA) protein have shown interesting results in experimental models for the treatment of traumatic spinal cord injury. By studying the interaction between BSA and PPPy/I by a quartz crystal microbalance (QCM) and docking, we obtained important results to elucidate possible cellular interactions and promote the use of these polymers as biomaterials. These measurements were also used to characterize the adsorption process using an equilibrium constant. In addition, atomic force microscopy (AFM) was used to obtain images of the QCM surface sensors before and after BSA adsorption. Furthermore, we carried out molecular dynamics simulations and molecular docking to characterize the molecular recognition between BSA and the previously reported PPPy/I structure. For this study, we used two combinatorial models that have not been tested. Thus, we could determine the electrostatic (ΔGele) and nonelectrostatic (ΔGnonelec) components of the free binding energy (ΔGb). We demonstrated that BSA is adsorbed on PPPy/I with an adsorption constant of K = 24.35 µ-1 indicating high affinity. This observation combined with molecular docking and binding free energy calculations showed that the interaction between BSA and both combinatorial models of the PPPy structure is spontaneous.

Discovery of Potential Noncovalent Inhibitors of Dehydroquinate Dehydratase from Methicillin-Resistant Staphylococcus aureus through Computational-Driven Drug Design.

Bacteria resistance to antibiotics is a concerning global health problem; in this context, methicillin-resistant Staphylococcus aureus (MRSA) is considered as a high priority by the World Health Organization. Furthermore, patients with a positive result for COVID-19 received early antibiotic treatment, a fact that potentially encourages the increase in antibiotic resistance. Therefore, there is an urgency to develop new drugs with molecular mechanisms different from those of the actual treatments. In this context, enzymes from the shikimate pathway, a route absent in humans, such as dehydroquinate dehydratase (DHQD), are considered good targets. In this work, a computer-aided drug design strategy, which involved exhaustive virtual screening and molecular dynamics simulations with MM-PBSA analysis, as well as an in silico ADMETox characterization, was performed to find potential noncovalent inhibitors of DHQD from MRSA (SaDHQD). After filtering the 997 million compounds from the ZINC database, 6700 compounds were submitted to an exhaustive virtual screening protocol. From these data, four molecules were selected and characterized (ZINC000005753647 (1), ZINC000001720488 (2), ZINC000082049768 (3), and ZINC000644149506 (4)). The results indicate that the four potential inhibitors interacted with residues important for substrate binding and catalysis, with an estimated binding free energy like that of the enzyme's substrate. Their ADMETox-predicted properties suggest that all of them support the structural characteristics to be considered good candidates. Therefore, the four compounds reported here are excellent option to be considered for future in vitro studies to design new SaDHQD noncovalent inhibitors and contribute to the search for new drugs against MRSA.

"Eritadenine as a regulator of anxiety Disorders: An experimental and docking Approach".

Uncertainty persists regarding the specific chemical causal factors and their corresponding behavioral effects in anxiety disorders. Commonly employed first-line treatments for anxiety target G protein-coupled receptors (GPCRs), including inhibitors of monoaminergic systems. Alternatively, emerging natural bioactive strategies offer potential for mitigating adverse effects. Recent investigations have implicated adenosine in anxiety-triggering mechanisms, while eritadenine, an adenosine analog derived from Shiitake mushroom, has displayed promising attributes. This study explores eritadenine's potential as a bioactive substance for anxiety disorders in mice, employing behavioral tests, pentobarbital-sleep induction, and molecular docking. Behavioral test results reveal a pronounced anxiolytic and sedative-hypnotic pharmacological effect of eritadenine. Our findings suggest that eritadenine may modulate locomotor functions mediated by adenosine receptors, with a stronger affinity for binding to A2AAR over A1AR, thus eliciting these effects.

B-Cell Lymphoma Intramedullary Tumor: Case Report and Systematic Review.

Intramedullary tumors represent the major cause of spinal cord injuries, and its symptoms include pain and weakness. Progressive weakness may concomitantly occur in the upper and lower limbs, along with lack of balance, spine tenderness, sensory loss, trophic changes of extremity, hyperreflexia, and clonus. The study protocol was in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A systematic search of the MEDLINE electronic database was performed to identify the studies reporting the clinical features of children and adults who presented with an intramedullary lymphoma. Twenty-one studies were included, reporting 25 cases. Manuscripts were excluded if the full-text article was not available, original data were not reported (e.g., review articles), or if the main disease was not intramedullary lymphoma. A structured data extraction form was employed to standardize the identification and retrieval of data from manuscripts. To enlighten the discussion, a case is also presented. An 82-year-old woman with Fitzpatrick skin type II, diagnosed and treated for non-Hodgkin's lymphoma 7 years ago, was admitted with mental confusion and memory loss for the past 2 months-evolving with recurring falls from her own height. One day before admission, she displayed Brown-Séquard syndrome. An expansive lesion from C2 to C4 in the cervical spinal cord was found and a hypersignal spinal cord adjacent was described at the bulb medullary transition to the C6-C7 level. A primary spinal cord tumor was considered, as well as a melanoma metastasis, due to the lesion's flame pattern. The patient presented a partial recovery of symptoms and a reduction of the spinal cord edema after being empirically treated with corticosteroids, but the lesion maintained its extent. Subsequently, a large diffuse B-cell lymphoma with nongerminal center was found in open body biopsy, infiltrating neural tissue. The main objective of the present study is to report a surgical case treated for a large diffuse B-cell lymphoma, in addition to presenting the results of a systematic review of primary intramedullary spinal cord lymphoma.

Ex Vivo and In Silico Approaches of Tracheal Relaxation through Calcium Channel Blockade of 6-Aminoflavone and Its Toxicological Studies in Murine Models.

Asthma is a condition in which a person's airways become inflamed, narrowed, and produce greater amounts of mucus than normal. It can cause shortness of breath, chest pain, coughing, or wheezing. In some cases, symptoms may be exacerbated. Thus, the current study was designed to determine the mechanism of action of 6-aminoflavone (6-NH2F) in ex vivo experiments, as well as to determine its toxicity in acute and sub-chronic murine models. Tissues were pre-incubated with 6-NH2F, and concentration-response curves to carbachol-induced contraction were constructed. Therefore, tracheal rings pre-treated with glibenclamide, 2-aminopyridine, or isoproterenol were contracted with carbachol (1 µM), then 6-NH2F relaxation curves were obtained. In other sets of experiments, to explore the calcium channel role in the 6-NH2F relaxant action, tissues were contracted with KCl (80 mM), and 6-NH2F was cumulatively added to induce relaxation. On the other hand, tissues were pre-incubated with the test sample, and after that, CaCl2 concentration-response curves were developed. In this context, 6-NH2F induced significant relaxation in ex vivo assays, and the effect showed a non-competitive antagonism pattern. In addition, 6-NH2F significantly relaxed the contraction induced by KCl and CaCl2, suggesting a potential calcium channel blockade, which was corroborated by in silico molecular docking that was used to approximate the mode of interaction with the L-type Ca2+ channel, where 6-NH2F showed lower affinity energy when compared with nifedipine. Finally, toxicological studies revealed that 6-NH2F possesses pharmacological safety, since it did not produce any toxic effect in both acute and sub-acute murine models. In conclusion, 6-aminoflavone exerted significant relaxation through calcium channel blockade, and the compound seems to be safe.

Computational study to find the goat serum albumin (GSA) binding site as A-esterase.

A-esterases are a classical term applied to enzymatic activity of the proteins by a mechanism not involving intermediate covalent phosphorylation, but requiring a divalent cation cofactor. Recently, a copper-dependent A-esterase activity has been identified in goat serum albumin (GSA) on the organophosphorus insecticide trichloronate. This hydrolysis was identified ex vivo with spectrophotometry and chromatography techniques. Albumin mechanism of action and catalytic site as Cu2+-dependent A-esterase are still unknown. Therefore, to know the copper bind to albumin is relevant. N-terminal sequence has been reported as the high affinity site for this cation, due to the histidine in position 3. The aim of this work in silico is to explore how occurs this metallic binding and active the esterase catalytic function. The GSA crystallized structure (PDB: 5ORI) was chosen for molecular docking and dynamics. A site-directed docking, for N-terminal site and a blind docking was done with trichloronate as ligand. Root-mean-square deviation and frequency plot was calculated to find the most frequent predicted structure and visualize the amino acids involved in binding site. The affinity energy in the blind docking (-5.80 kcal/mol) is almost twice lower than site-directed docking (-3.81 kcal/mol) and N-terminal amino acids do not appear in the most repeated structure binding site, suggesting that the protein has a site with higher affinity to the trichloronate ligand. His145 could be involved in the binding site as has been reported in previous studies.

Unfolding and Aggregation Pathways of Variable Domains from Immunoglobulin Light Chains.

Light chain amyloidosis is the most common form of systemic amyloidosis. This disease is caused by the formation and deposition of amyloid fibers made from immunoglobulin light chains. Environmental conditions such as pH and temperature can affect protein structure and induce the development of these fibers. Several studies have shed light on the native state, stability, dynamics, and final amyloid state of these proteins; however, the initiation process and the fibril formation pathway remain poorly understood structurally and kinetically. To study this, we analyzed the unfolding and aggregation process of the 6aJL2 protein under acidic conditions, with temperature changes, and upon mutation, using biophysical and computational techniques. Our results suggest that the differences in amyloidogenicity displayed by 6aJL2 under these conditions are caused by traversing different aggregation pathways, including unfolded intermediates and the formation of oligomers.

A Putative New Role of Tv-PSP1 Recognizes IRE and ERE Hairpin Structures from Trichomonas vaginalis.

To understand whether protein Tv-PSP1 from Trichomonas vaginalis recognizes mRNA parasite stem-loop structures, we conducted REMSA and intrinsic fluorescence assays. We found the recombinant Tv-PSP1 structure, determined with X-ray crystallography, showed unusual thermal stability of the quaternary structure, associated with a disulfide bridge CYS76-CYS104. To gain deeper insight into the Tv-PSP1 interaction with mRNA stem-loops (mRNAsl) and its relationship with thermal stability, we also used an integrated computational protocol that combined molecular dynamics simulations, docking assays, and binding energy calculations. Docking models allowed us to determine a putative contact surface interaction region between Tv-PSP1 and mRNAsl. We determined the contributions of these complexes to the binding free energy (ΔGb) in the electrostatic (ΔGelec) and nonelectrostatic (ΔGnon-elec) components using the Adaptive Poisson-Boltzmann Solver (APBS) program. We are the first, to the best of our knowledge, to show the interaction between Tv-PSP1 and the stem-loop structures of mRNA.

A potent virucidal activity of functionalized TiO2 nanoparticles adsorbed with flavonoids against SARS-CoV-2.

The coronavirus SARS-CoV-2 has caused a pandemic with > 550 millions of cases and > 6 millions of deaths worldwide. Medical management of COVID-19 relies on supportive care as no specific targeted therapies are available yet. Given its devastating effects on the economy and mental health, it is imperative to develop novel antivirals. An ideal candidate will be an agent that blocks the early events of viral attachment and cell entry, thereby preventing viral infection and spread. This work reports functionalized titanium dioxide (TiO2)-based nanoparticles adsorbed with flavonoids that block SARS-CoV-2 entry and fusion. Using molecular docking analysis, two flavonoids were chosen for their specific binding to critical regions of the SARS-CoV-2 spike glycoprotein that interacts with the host cell angiotensin-converting enzyme-2 (ACE-2) receptor. These flavonoids were adsorbed onto TiO2 functionalized nanoparticles (FTNP). This new nanoparticulate compound was assayed in vitro against two different coronaviruses; HCoV 229E and SARS-CoV-2, in both cases a clear antiviral effect was observed. Furthermore, using a reporter-based cell culture model, a potent antiviral activity is demonstrated. The adsorption of flavonoids to functionalized TiO2 nanoparticles induces a ~ threefold increase of that activity. These studies also indicate that FTNP interferes with the SARS-CoV-2 spike, impairing the cell fusion mechanism. KEY POINTS/HIGHLIGHTS: • Unique TiO2 nanoparticles displaying flavonoid showed potent anti-SARS-CoV-2 activity. • The nanoparticles precisely targeting SARS-CoV-2 were quantitatively verified by cell infectivity in vitro. • Flavonoids on nanoparticles impair the interactions between the spike glycoprotein and ACE-2 receptor.

Multiadducts of C60 Modulate Amyloid-ß Fibrillation with Dual Acetylcholinesterase Inhibition and Antioxidant Properties: In Vitro and In Silico Studies.

BACKGROUND: Amyloid-ß (Aß) fibrils induce cognitive impairment and neuronal loss, leading to onset of Alzheimer's disease (AD). The inhibition of Aß aggregation has been proposed as a therapeutic strategy for AD. Pristine C60 has shown the capacity to interact with the Aß peptide and interfere with fibril formation but induces significant toxic effects in vitro and in vivo. OBJECTIVE: To evaluate the potential of a series of C60 multiadducts to inhibit the Aß fibrillization. METHODS: A series of C60 multiadducts with four to six diethyl malonyl and their corresponding disodium-malonyl substituents were synthesized as individual isomers. Their potential on Aß fibrillization inhibition was evaluated in vitro, in cellulo, and silico. Antioxidant activity, acetylcholinesterase inhibition capacity, and toxicity were assessed in vitro. RESULTS: The multiadducts modulate Aß fibrils formation without inducing cell toxicity, and that the number and polarity of the substituents play a significant role in the adducts efficacy to modulate Aß aggregation. The molecular mechanism of fullerene-Aß interaction and modulation was identified. Furthermore, the fullerene derivatives exhibited antioxidant capacity and reduction of acetylcholinesterase activity. CONCLUSION: Multiadducts of C60 are novel multi-target-directed ligand molecules that could hold considerable promise as the starting point for the development of AD therapies.

6-Amino-3-Methyl-4-(2-nitrophenyl)-1,4-Dihydropyrano[2,3-c]Pyrazole-5-Carbonitrile Shows Antihypertensive and Vasorelaxant Action via Calcium Channel Blockade.

Several 4H-pyran derivatives were designed and synthesized previously as vasorelaxant agents for potential antihypertensive drugs. In this context, the objective of the present investigation was to determine the functional mechanism of vasorelaxant action of 6-amino-3-methyl-4-(2-nitrophenyl)-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (1: ) and its in vivo antihypertensive effect. Thus, compound 1: showed significant vasorelaxant action on isolated aorta rat rings pre-contracted with serotonin or noradrenaline, and the effect was not endothelium-dependent. Compound 1: induced a significant relaxant effect when aortic rings were contracted with KCl (80 mM), indicating that the main mechanism of action is related to L-type calcium channel blockade. Last was corroborated since compound 1: induced a significant concentration-dependent lowering of contraction provoked by cumulative CaCl2 adding. Moreover, compound 1: was capable to block the contraction induced by FPL 64176, a specific L-type calcium channel agonist, in a concentration-dependent manner. On the other hand, docking studies revealed that compound 1: interacts on two possible sites of the L-type calcium channel and it had better affinity energy (-7.80+/-0.00 kcal/mol on the best poses) than nifedipine (-6.86+/-0.14 kcal/mol). Finally, compound 1: (50 mg/kg) showed significant antihypertensive activity, lowering the systolic and diastolic blood pressure on spontaneously hypertensive rats (SHR) without modifying heart rate.

Rare complication of ventriculoperitoneal shunt: Ectopic distal catheter in a Grynfeltt hernia - case report.

BACKGROUND: Ventriculoperitoneal shunts (VPSs) insertion is the most common used intervention in cases of hydrocephalus. The main postoperative complications are infections and catheter obstructions. Although the literature has well-documented cases describing migration of the distal catheter, this rare presentation can become more confusing when occurring in conjunction with some unusual preexistent morbidity in the patient, as a Grynfeltt hernia. CASE DESCRIPTION: This study reports a rare case of a VPS postoperative migration, in which the distal catheter exits the abdominal cavity through a Grynfeltt hernia. This condition was not discovered until the catheter fistulated through the overlying skin. The Grynfeltt hernia is the most uncommon among the lumbar ones and it's asymptomatic in the majority of the cases, being hardly diagnosed. CONCLUSION: The unusualness of the reported case deserves furthermore discussion to properly evaluate these underlying mechanisms of catheter migration.

In Vitro Anti-Tubulin Activity on MCF10A Cell Line and In Silico Rigid/Semiflexible-Residues Docking, of Two Lignans from Bursera Fagaroides var. Fagaroides.

Podophyllotoxins are natural lignans with known cytotoxic activity on several cell lines. The structural basis for their actions is mainly by the aryltetralin-lignan skeleton. Authors have proposed a cytotoxic mechanism of podophyllotoxins through the topoisomerase-II inhibition activity; however, several studies have also suggested that podophyllotoxins can inhibit the microtubules polymerization. In this work, the two possible mechanisms of action of two previously isolated compounds from the stem bark of Bursera fagaroides var. fagaroides: acetylpodophyllotoxin (1) and 5'-desmethoxydeoxypodophyllotoxin (2), was analyzed. An in vitro anti-tubulin epifluorescence on the MCF10A cell line and enzymatic topoisomerase II assays were performed. The binding affinities of compounds 1 and 2 in the colchicine binding site of tubulin by using rigid- and semiflexible-residues were calculated and compared using in silico docking methods. The two lignans were active by the in vitro anti-tubulin assay but could not inhibit TOP2 activity. In the in silico analysis, the binding modes of compounds into both rigid- and semiflexible-residues of tubulin were predicted, and only for the semiflexible docking method, a linear correlation between the dissociation constant and IC50 previously reported was found. Our results suggest that a simple semiflexible-residues modification in docking methods could provide an in vitro correlation when analyzing very structurally similar compounds.

Spinal intramedullary abscess due to Candida albicans in an immunocompetent patient: A rare case report.

BACKGROUND: A spinal intramedullary abscess is a rare clinical entity in which patients classically present with a subacute myelopathy and progressive paraplegia, sensory deficits, and/or bowel and bladder dysfunction. We report the second case of spinal intramedullary abscess caused by Candida albicans to ever be published and the first case of its kind to be surgically managed. CASE DESCRIPTION: A 44-year-old female presented with severe lumbar pain associated with paraparesis, incontinence, and paraplegia. She reported multiple hospital admissions and had a history of seizures, having already undergone treatment for neurotuberculosis and fungal infection of the central nervous system unsuccessfully. Nevertheless, no laboratory evidence of immunosuppression was identified on further investigation. Magnetic resonance imaging showed a D10-D11, well-circumscribed, intramedullary mass within the conus, which was hypointense on T1-weighted imaging and hyperintense on T2/STIR weighted. The patient underwent surgery for removal and biopsy of the lesion, which provided the diagnosis of an intramedullary abscess caused by C. albicans, a very rare condition with only one case reported in literature so far. CONCLUSION: C. albicans intramedullary abscess is a very rare clinical entity, especially in immunocompetent patients. We highlight C. albicans as an important etiology that must be considered in differential diagnosis. Critical evaluation of every case, early diagnosis, timely referral and surgical management of the abscess is essential to improve neurological outcome.