One His, two His the emerging roles of histidine in cellular nickel trafficking.

Biological environments present a complex array of metal-binding ligands. Metal-binding proteins have been the overwhelming focus of study because of their important and well-defined biological roles. Consequently, the presence of functional low molecular weight (LMW) metal-ligand complexes has been overlooked in terms of their roles in metallobiochemistry, particularly within cells. Recent studies in microbial systems have illuminated the different roles of L-histidine in nickel uptake, gene expression, and metalloenzyme maturation. In this focused critical review, these roles are surveyed in the context of the coordination chemistry of Ni(II) ions and the amino acid histidine, and the physico-chemical properties of nickel complexes of histidine. These complexes are fundamentally important to cellular metal homeostasis and further work is needed to fully define their contributions.

Gamma amplitude-envelope correlations are strongly elevated within hyperexcitable networks in focal epilepsy.

Methods to quantify cortical hyperexcitability are of enormous interest for mapping epileptic networks in patients with focal epilepsy. We hypothesize that, in the resting state, cortical hyperexcitability increases firing-rate correlations between neuronal populations within seizure onset zones (SOZs). This hypothesis predicts that in the gamma frequency band (40-200 Hz), amplitude envelope correlations (AECs), a relatively straightforward measure of functional connectivity, should be elevated within SOZs compared to other areas. To test this prediction, we analyzed archived samples of interictal electrocorticographic (ECoG) signals recorded from patients who became seizure-free after surgery targeting SOZs identified by multiday intracranial recordings. We show that in the gamma band, AECs between nodes within SOZs are markedly elevated relative to those elsewhere. AEC-based node strength, eigencentrality, and clustering coefficient are also robustly increased within the SOZ with maxima in the low-gamma band (permutation test Z-scores > 8) and yield moderate discriminability of the SOZ using ROC analysis (maximal mean AUC ~ 0.73). By contrast to AECs, phase locking values (PLVs), a measure of narrow-band phase coupling across sites, and PLV-based graph metrics discriminate the seizure onset nodes weakly. Our results suggest that gamma band AECs may provide a clinically useful marker of cortical hyperexcitability in focal epilepsy.

Clinical management, monitoring, and prophylaxis of adverse events of special interest associated with datopotamab deruxtecan.

Antibody drug conjugates (ADCs) are an emerging class of treatments designed to improve efficacy and decrease toxicity compared with other systemic therapies through the selective delivery of cytotoxic agents to tumor cells. Datopotamab deruxtecan (Dato-DXd) is a novel ADC comprising a topoisomerase I inhibitor payload and a monoclonal antibody directed to trophoblast cell-surface antigen 2 (TROP2), a protein that is broadly expressed in several types of solid tumors. Dato-DXd is being investigated across multiple solid tumor indications. In the ongoing, first-in-human TROPION-PanTumor01 phase I study (ClinicalTrials.gov: NCT03401385), encouraging and durable antitumor activity and a manageable safety profile was demonstrated in patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor2-negative breast cancer (HR+/HER2- BC), triple-negative breast cancer (TNBC), and non-small cell lung cancer (NSCLC). Improved understanding of the adverse events (AEs) that are associated with Dato-DXd and their optimal management is essential to ensure safe and successful administration. Interstitial lung disease/pneumonitis, infusion-related reactions, oral mucositis/stomatitis, and ocular surface events have been identified as AEs of special interest (AESIs) for which appropriate prevention, monitoring, and management is essential. This article summarizes the incidence of AESIs among patients with HR+/HER2- BC, TNBC, and NSCLC reported in TROPION-PanTumor01. We report our recommendations for AESI prophylaxis, early detection, and management, using experience gained from treating AESIs that occur with Dato-DXd in clinical trials.

TROPION-Lung08: phase III study of datopotamab deruxtecan plus pembrolizumab as first-line therapy for advanced NSCLC.

Pembrolizumab monotherapy is a standard first-line treatment for PD-L1-high advanced non-small-cell lung cancer (NSCLC) without actionable genomic alterations (AGA). However, few patients experience long-term disease control, highlighting the need for more effective therapies. Datopotamab deruxtecan (Dato-DXd), a novel trophoblast cell-surface antigen 2-directed antibody-drug conjugate, showed encouraging safety and antitumor activity with pembrolizumab in advanced NSCLC. We describe the rationale and design of TROPION-Lung08, a phase III study evaluating safety and efficacy of first-line Dato-DXd plus pembrolizumab versus pembrolizumab monotherapy in patients with advanced/metastatic NSCLC without AGAs and with PD-L1 tumor proportion score ≥50%. Primary end points are progression-free survival and overall survival; secondary end points include objective response rate, duration of response, safety and presence of antidrug antibodies. Clinical trial registration: NCT05215340 (ClinicalTrials.gov).

More than half of patients with non-small-cell lung cancer (NSCLC) are diagnosed when their tumor is advanced (unlikely to be cured with currently available treatments) or metastatic (spread to other parts of the body). These patients have poor survival outcomes. NSCLCs can grow by using a protein called PD-L1 to escape from the immune system. Pembrolizumab is an immunotherapy that targets PD-1, the protein on immune cells that detects PD-L1. Because of this, pembrolizumab prevents the tumor from escaping the immune system by blocking the interaction of PD-L1 with PD-1. Patients whose NSCLC tumors express PD-L1 often respond to pembrolizumab at first but, for most of these patients, their cancer eventually comes back. An investigational drug called datopotamab deruxtecan (Dato-DXd) is a type of therapy called an antibody­drug conjugate that delivers chemotherapy to tumors using an antibody. The antibody in Dato-DXd is directed against a protein called TROP2, which is commonly expressed by tumor cells. Results from early studies show that combining pembrolizumab with Dato-DXd may work well for patients with solid tumors, including NSCLC. This study will look at the benefits and side effects of Dato-DXd added to pembrolizumab compared with pembrolizumab alone as a first treatment option for patients with advanced NSCLC and high levels of PD-L1.

Glycyrrhizin, an inhibitor of HMGB1 induces autolysosomal degradation function and inhibits Helicobacter pylori infection.

BACKGROUND: Helicobacter pylori is a key agent for causing gastric complications linked with gastric disorders. In response to infection, host cells stimulate autophagy to maintain cellular homeostasis. However, H. pylori have evolved the ability to usurp the host's autophagic machinery. High mobility group box1 (HMGB1), an alarmin molecule is a regulator of autophagy and its expression is augmented during infection and gastric cancer. Therefore, this study aims to explore the role of glycyrrhizin (a known inhibitor of HMGB1) in autophagy during H. pylori infection. MAIN METHODS: Human gastric cancer (AGS) cells were infected with the H. pylori SS1 strain and further treatment was done with glycyrrhizin. Western blot was used to examine the expression of autophagy proteins. Autophagy and lysosomal activity were monitored by fluorescence assays. A knockdown of HMGB1 was performed to verify the effect of glycyrrhizin. H. pylori infection in in vivo mice model was established and the effect of glycyrrhizin treatment was studied. RESULTS: The autophagy-lysosomal pathway was impaired due to an increase in lysosomal membrane permeabilization during H. pylori infection in AGS cells. Subsequently, glycyrrhizin treatment restored the lysosomal membrane integrity. The recovered lysosomal function enhanced autolysosome formation and concomitantly attenuated the intracellular H. pylori growth by eliminating the pathogenic niche. Additionally, glycyrrhizin treatment inhibited inflammation and improved gastric tissue damage in mice. CONCLUSION: This study showed that inhibiting HMGB1 restored lysosomal activity to ameliorate H. pylori infection. It also demonstrated the potential of glycyrrhizin as an antibacterial agent to address the problem of antimicrobial resistance.

The structure of the high-affinity nickel-binding site in the Ni,Zn-HypA•UreE2 complex.

The maturation pathway for the nickel-dependent enzyme urease utilizes the protein UreE as a metallochaperone to supply Ni(II) ions. In Helicobacter pylori urease maturation also requires HypA and HypB, accessory proteins that are commonly associated with hydrogenase maturation. Herein we report on the characterization of a protein complex formed between HypA and the UreE2 dimer. Nuclear magnetic resonance (NMR) coupled with molecular modelling show that the protein complex apo, Zn-HypA•UreE2, forms between the rigorously conserved Met-His-Glu (MHE motif) Ni-binding N-terminal sequence of HypA and the two conserved His102A and His102B located at the dimer interface of UreE2. This complex forms in the absence of Ni(II) and is supported by extensive protein contacts that include the use of the C-terminal sequences of UreE2 to form additional strands of ß-sheet with the Ni-binding domain of HypA. The Ni-binding properties of apo, Zn-HypA•UreE2 and the component proteins were investigated by isothermal titration calorimetry using a global fitting strategy that included all of the relevant equilibria, and show that the Ni,Zn-HypA•UreE2 complex contains a single Ni(II)-binding site with a sub-nanomolar KD. The structural features of this novel Ni(II) site were elucidated using proteins produced with specifically deuterated amino acids, protein point mutations, and the analyses of X-ray absorption spectroscopy, hyperfine shifted NMR features, as well as molecular modeling coupled with quantum-mechanical calculations. The results show that the complex contains a six-coordinate, high-spin Ni(II) site with ligands provided by both component proteins.

Asiatic acid inhibits intracellular Shigella flexneri growth by inducing antimicrobial peptide gene expression.

AIMS: A rapid rise in resistance to conventional antibiotics for Shigella spp. has created a problem in treating shigellosis. Hence, there is an urgent need for new and non-conventional anti-bacterial agents. The aim of this study is to show how Asiatic acid, a plant-derived compound, inhibits the intracellular growth of Shigella flexneri. METHODS AND RESULTS: Shigella flexneri sensitive and resistant strains were used for checking antimicrobial activity of Asiatic acid by gentamicin protection assay. Asiatic acid inhibited the intracellular growth of all strains. Gene expression analysis showed antimicrobial peptide (AMP) up-regulation by Asiatic acid in intestinal cells. Further western blot analysis showed that ERK, p38, and JNK are activated by Asiatic acid. ELISA was performed to check IL-8, IL-6, and cathelicidin secretion. The antibacterial effect of Asiatic acid was further verified in an in vivo mouse model. CONCLUSIONS: The reason behind the antibacterial activities of Asiatic acid is probably over-expression of antimicrobial peptide genes. Besides, direct antimicrobial activities, antimicrobial peptides also carry immunomodulatory activities. Here, Asiatic acid increased IL-6 and IL-8 secretion to induce inflammation. Overall, Asiatic acid up-regulates antimicrobial peptide gene expression and inhibits intracellular S. flexneri growth. Moreover, Asiatic acid reduced bacterial growth and recovered intestinal tissue damages in in vivo mice model.

Pro5 is not essential for the formation of 'Ni-hook' in nickel superoxide dismutase.

The N-terminus of nickel-dependent superoxide dismutase (NiSOD) forms a structural motif known as the "Ni-hook," where the peptide wraps around the metal to bring cysteine-2 and cysteine-6 into spatial proximity, allowing these residues to coordinate in a cis-geometry. A highly conserved proline-5 residue in the Ni-hook adopts a cis-conformation that is widely considered important for its formation. Herein, we investigate this role by point mutation of Pro5 to alanine. The results obtained show that the variant exhibits wild-type-like redox catalysis and features a Ni(III) center very similar to that found in enzyme. Structural analysis using X-ray absorption spectroscopy of the nickel sites in as-isolated P5A-NiSOD reveals changes in the variant and are consistent with a six-coordinate Ni site with (N/O)4S2 coordination. These changes are attributed to changes in the Ni(II) site structure. Nickel-binding studies using isothermal titration calorimetry reveal two binding events with Kd = 25(20) nM, and 250(60) nM. These events are attributed to i) Ni(II) binding to a preformed Ni-hook containing cis-Pro5 and ii) the combination of trans- to cis- isomerization upon Ni(II) binding, respectively. The higher-affinity binding event is absent in P5A-NiSOD, an observation attributed to the low abundance of the cis-Ala5 isomer in the apo-protein.

Distinct nutritional and endocrine regulation of prothoracic gland activities underlies divergent life history strategies in Manduca sexta and Drosophila melanogaster.

Life history trade-offs lead to various strategies that maximize fitness, but the developmental mechanisms underlying these alternative strategies continue to be poorly understood. In insects, trade-offs exist between size and developmental time. Recent studies in the fruit fly Drosophila melanogaster have suggested that the steroidogenic prothoracic glands play a key role in determining the timing of metamorphosis. In this study, the nutrient-dependent growth and transcriptional activation of prothoracic glands were studied in D. melanogaster and the tobacco hornworm Manduca sexta. In both species, minimum viable weight (MVW) was associated with activation of ecdysteroid biosynthesis genes and growth of prothoracic gland cells. However, the timing of MVW attainment in M. sexta is delayed by the presence of the sesquiterpenoid hormone, juvenile hormone (JH), whereas in D. melanogaster it is not. Moreover, in D. melanogaster, the transcriptional regulation of ecdysteroidogenesis becomes nutrient-independent at the MVW/critical weight (CW) checkpoint. In contrast, in M. sexta, starvation consistently reduced transcriptional activation of ecdysteroid biosynthesis genes even after CW attainment, indicating that the nature of CW differs fundamentally between the two species. In D. melanogaster, the prothoracic glands dictate the timing of metamorphosis even in the absence of nutritional inputs, whereas in M. sexta, prothoracic gland activity is tightly coupled to the nutritional status of the body, thereby delaying the onset of metamorphosis before CW attainment. We propose that selection for survival under unpredictable nutritional availability leads to the evolution of increased modularity in both morphological and endocrine traits.

Structural, Photophysical, and Photochemical Characterization of Zinc Protoporphyrin IX in a Dimeric Variant of an Iron Storage Protein: Insights into the Mechanism of Photosensitized H2 Generation.

Some of us have previously reported the preparation of a dimeric form of the iron storage protein, bacterioferritin (Bfr), in which the native heme b is substituted with the photosensitizer, Zn(II)-protoporphyrin IX (ZnPP-Bfr dimer). We further showed that the ZnPP-Bfr dimer can serve as a photosensitizer for platinum-catalyzed H2 generation in aqueous solution without the usually added electron relay between photosensitizer and platinum ( Clark , E. R. , Inorg. Chem. 2017 , 56 , 4584 - 4593 ). We proposed reductive or oxidative quenching pathways involving the ZnPP anion radical (ZnPP•-) or the ZnPP cation radical, (ZnPP•+), respectively. The present report describes structural, photophysical, and photochemical properties of the ZnPP in the ZnPP-Bfr dimer. X-ray absorption spectroscopic studies at 10 K showed a mixture of five- and six-coordinated Zn centers with axial coordination by one long Zn-SγMet distance of ∼2.8 Å and ∼40% having an additional shorter Zn-S distance of ∼2.4 Å, in addition to the expected 4 nitrogen atom coordination from the porphyrin. The ZnPP in ZnPP-Bfr dimer was prone to photosensitized oxidation to ZnPP•+. The ZnPP•+ was rapidly reduced by ascorbic acid, which we previously determined was essential for photosensitized H2 production in this system. These results are consistent with an oxidative quenching pathway involving electron transfer from 3ZnPP* to platinum, which may be assisted by a flexible ZnPP axial coordination sphere. However, the low quantum yield for H2 production (∼1%) in this system could make reductive quenching difficult to detect, and can, therefore, not be completely ruled out. The ZnPP-Bfr dimer provides a simple but versatile framework for mechanistic assessment and optimization of porphyrin-photosensitized H2 generation without an electron relay between porphyrin and the platinum catalyst.

Structure and dynamics of Helicobacter pylori nickel-chaperone HypA: an integrated approach using NMR spectroscopy, functional assays and computational tools.

Helicobacter pylori HypA (HpHypA) is a metallochaperone necessary for maturation of [Ni,Fe]-hydrogenase and urease, the enzymes required for colonization and survival of H. pylori in the gastric mucosa. HpHypA contains a structural Zn(II) site and a unique Ni(II) binding site at the N-terminus. X-ray absorption spectra suggested that the Zn(II) coordination depends on pH and on the presence of Ni(II). This study was performed to investigate the structural properties of HpHypA as a function of pH and Ni(II) binding, using NMR spectroscopy combined with DFT and molecular dynamics calculations. The solution structure of apo,Zn-HpHypA, containing Zn(II) but devoid of Ni(II), was determined using 2D, 3D and 4D NMR spectroscopy. The structure suggests that a Ni-binding and a Zn-binding domain, joined through a short linker, could undergo mutual reorientation. This flexibility has no physiological effect on acid viability or urease maturation in H. pylori. Atomistic molecular dynamics simulations suggest that Ni(II) binding is important for the conformational stability of the N-terminal helix. NMR chemical shift perturbation analysis indicates that no structural changes occur in the Zn-binding domain upon addition of Ni(II) in the pH 6.3-7.2 range. The structure of the Ni(II) binding site was probed using 1H NMR spectroscopy experiments tailored to reveal hyperfine-shifted signals around the paramagnetic metal ion. On this basis, two possible models were derived using quantum-mechanical DFT calculations. The results provide a comprehensive picture of the Ni(II) mode to HpHypA, important to rationalize, at the molecular level, the functional interactions of this chaperone with its protein partners.

Prophylactic role of taurine and its derivatives against diabetes mellitus and its related complications.

Taurine is a conditionally essential amino acid present in the body in free form. Mammalian taurine is synthesized in the pancreas via the cysteine sulfinic acid pathway. Anti-oxidation and anti-inflammation are two main properties through which it exerts its therapeutic effects. Many studies have shown its excellent therapeutic potential against diabetes mellitus and related complications like diabetic neuropathy, retinopathy, nephropathy, hematological dysfunctions, reproductive dysfunctions, liver and pancreas related complications etc. Not only taurine, a number of its derivatives have also been reported to be important in ameliorating diabetic complications. The present review has been aimed to describe the importance of taurine and its derivatives against diabetic metabolic syndrome and related complications.

Perspectives of the Nrf-2 signaling pathway in cancer progression and therapy.

The Nuclear factor erythroid2-related factor2 (Nrf2), a master regulator of redox homoeostasis, is a key transcription factor regulating a wide array of genes for antioxidant and detoxification enzymes. It protects organs from various kinds of toxic insults. On the other hand, activation of Nrf2 is also correlated with cancer progression and chemoresistance. Downregulation of Nrf2 activity has attracted an increasing amount of attention as it may provide an alternative cancer therapy. In this review, we examine recent studies on roles of Nrf2 in several pathophysiological conditions emphasising cancer. We discuss elaborately the current knowledge on Nrf2 regulation including KEAP1-dependent and KEAP1-independent cascades. KEAP1/Nrf2 system is a master regulator of cellular response against a variety of environmental stresses. We also highlight several tightly controlled regulations of Nrf2 by numerous proteins, small molecules, toxic metals, etc. In addition, we evaluate the possible therapeutic approaches of increasing chemosensitivity via modulating Nrf2 signaling.

New insights into the ameliorative effects of ferulic acid in pathophysiological conditions.

Ferulic acid, a natural phytochemical has gained importance as a potential therapeutic agent by virtue of its easy commercial availability, low cost and minimal side-effects. It is a derivative of curcumin and possesses the necessary pharmacokinetic properties to be retained in the general circulation for several hours. The therapeutic effects of ferulic acid are mediated through its antioxidant and anti-inflammatory properties. It exhibits different biological activities such as anti-inflammatory, anti-apoptotic, anti-carcinogenic, anti-diabetic, hepatoprotective, cardioprotective, neuroprotective actions, etc. The current review addresses its therapeutic effects under different pathophysiological conditions (eg. cancer, cardiomyopathy, skin disorders, brain disorders, viral infections, diabetes etc.).