Colony Stimulating Factor-1 Receptor: An emerging target for neuroinflammation PET imaging and AD therapy.

Although neuroinflammation is a significant pathogenic feature of many neurologic disorders, its precise function in-vivo is still not completely known. PET imaging enables the longitudinal examination, quantification, and tracking of different neuroinflammation biomarkers in living subjects. Particularly, PET imaging of Microglia, specialised dynamic immune cells crucial for maintaining brain homeostasis in central nervous system (CNS), is crucial for staging the neuroinflammation. Colony Stimulating Factor- 1 Receptor (CSF-1R) PET imaging is a novel method for the quantification of neuroinflammation. CSF-1R is mainly expressed on microglia, and neurodegenerative disorders greatly up-regulate its expression. The present review primarily focuses on the development, pros and cons of all the CSF-1R PET tracers reported for neuroinflammation imaging. Apart from neuroinflammation imaging, CSF-1R inhibitors are also reported for the therapy of neurodegenerative diseases such as Alzheimer's disease (AD). AD is a prevalent, advancing, and fatal neurodegenerative condition that have the characteristic feature of persistent neuroinflammation and primarily affects the elderly. The aetiology of AD is profoundly influenced by amyloid-beta (Aß) plaques, intracellular neurofibrillary tangles, and microglial dysfunction. Increasing evidence suggests that CSF-1R inhibitors (CSF-1Ri) can be helpful in preclinical models of neurodegenerative diseases. This review article also summarises the most recent developments of CSF-1Ri-based therapy for AD.

Current Status of Our Understanding for Brain Integrated Functions and its Energetics.

Human/animal brain is a unique organ with substantially high metabolism but it contains no energy reserve that is the reason it requires continuous supply of O2 and energy fluxes through CBF. The main source of energy remains glucose as the other biomolecules do not able to cross the blood-brain barrier. The speed of glucose metabolism is heterogeneous throughout the brain. One of the major flux consumption is Neuron-astrocyte cycling of glutamate and glutamine in glutamatergic neurons (approximately 80% of glucose metabolism in brain). The quantification of cellular glucose and other related substrate in resting, activated state can be analyzed through [18 F]FDG -positron-emission tomography (studying CMRglc) and [13 C/31P -MRS: for neuroenergetics & neurotransmitter cycling &31P-MRS: for energy induction & redox state). Merging basic in vitro studies with these techniques will help to develop new treatment paradigms for human brain diseased conditions.

Acetamidobenzoxazolone scaffold as a promising translocator protein (18 kDa, TSPO) marker for neuroinflammation imaging: Advancement in last decennial period.

Inflammation has been linked to the onset and progression of a wide range of neuropathological disorders. The well-conserved outer mitochondrial membrane 18 kDa translocator protein (TSPO) is perceived as an in vivo neuroinflammation marker. A dearth of a reference region, genetic disparity influencing the ligand's affinity for TSPO, and a substantial signal in the endothelium of the brain veins contributes toward complications in quantifying TSPO positron emission tomography (PET) image. Up to the present time several radiotracers based on different pharmacophore such as (R)[11 C]PK11195, [18 F]DPA714, [11 C]PBR28, [11 C]ER176, and many more have been recognized for envisaging the prominent TSPO level observed in neurological conditions. Recently acetamidobenzoxazolone (ABO) scaffold, a bicyclic ring system composed of a phenyl ring fused to a carbamate and its substituted radiolabelled analogues especially at C-5 position has evidenced encouraging outcomes as next generation of TSPO PET ligands. Diverse ABO framework-based TSPO ligands have been designed embracing imperative aspects such as lipophilicity, metabolic profile, and capability to penetrate the blood-brain barrier apart from least effect of polymorphism (rs6971). Over the years numerous systematic literature reviews compiling different structural class of TSPO ligands characterized on the grounds of their binding affinity and metabolite profile have been reported but none is especially focused toward a fascinating benzoxazolone scaffold. This review exclusively bestows an overview of the recent advancements on ABO derivatives with neuroinflammation imaging potential and emphases on the structural features accountable for visualizing TSPO in-vivo with collation of published reports during last 10 years.

Benzoxazolone-arylpiperazinyl scaffold-based PET ligand for 5-HT7 : Synthesis and biological evaluation.

Efforts are underway to improve the diagnosis and treatment for neurological disorders like depression, anxiety, epilepsy, and schizophrenia. The G-protein-coupled receptors (GPCRs) 5-HT7   receptor, the most recently identified member of 5-HT receptor family dysregulation has an association with various central nervous system (CNS) disorders and its ligands have an edge as potential therapeutics. Here, we report the synthesis, characterization, and biological evaluation of diversely substituted methoxy derivatives of 2-benzoxazolone arylpiperazine for targeting 5-HT7  receptors. Out of all derivatives, only C-2 substituted derivative, 3-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butyl)benzoxazol-2(3H)-one/ABO demonstrate a high affinity for human 5-HT7 receptors. [11 C]ABO was obtained by O-methylation of desmethyl-precursor using [11 C]CH3 OTf in the presence of NaOH giving a high radiochemical yield of 25 ± 12% (decay-corrected, n = 7) with stability up to 1.5 h postradiolabeling. In vitro autoradiography displays binding of [11 C]ABO in accordance with 5-HT7 distribution with a decrease of approximately 80% and 40% activity in the hippocampus and cerebellum brain region when administered with 10 µM cold ligand. Prefatory positron emission tomography scan results in Sprague-Dawley (SD) rat brain revealed fast and high radioactivity build-up in 5-HT7 receptor-rich regions, namely, the hippocampus (2.75 ± 0.16 SUV) and the cerebral cortex (2.27 ± 0.02 SUV) establishing selective targeting of [11 C]ABO. In summary, these pieces of data designate [11 C]ABO as a promising 5-HT7  receptor ligand that can have possible roles in clinics after its further optimization on different animal models.

Mapping of Translocator Protein (18 kDa) in Peripheral Sterile Inflammatory Disease and Cancer through PET Imaging.

Positron emission tomography (PET) imaging of the translocator 18 kDa protein (TSPO) with radioligands has become an effective means of research in peripheral inflammatory conditions that occur in many diseases and cancers. The peripheral sterile inflammatory diseases (PSIDs) are associated with a diverse group of disorders that comprises numerous enduring insults including the cardiovascular, respiratory, gastrointestinal, or musculoskeletal system. TSPO has recently been introduced as a potential biomarker for peripheral sterile inflammatory diseases (PSIDs). The major critical issue related to PSIDs is its timely characterization and localization of inflammatory foci for proper therapy of patients. As an alternative to metabolic imaging, protein imaging expressed on immune cells after activation is of great importance. The five transmembrane domain translocator protein-18 kDa (TSPO) is upregulated on the mitochondrial cell surface of macrophages during inflammation, serving as a potential ligand for PET tracers. Additionally, the overexpressed TSPO protein has been positively correlated with various tumor malignancies. In view of the association of escalated TSPO expression in both disease conditions, it is an immensely important biomarker for PET imaging in oncology and PSIDs. In this review, we summarize the most outstanding advances on TSPO-targeted PSIDs and cancer in the development of TSPO ligands as a potential diagnostic tool, specifically discussing the last five years.

Zinc complex of tryptophan appended 1,4,7,10-tetraazacyclododecane as potential anticancer agent: Synthesis and evaluation.

With the rising incidences of cancer cases, the quest for new metal based anticancer drugs has led to extensive research in cancer biology. Zinc complexes of amino acid residue side chains are well recognized for hydrolysis of phosphodiester bond in DNA at faster rate. In the presented work, a Zn(II) complex of cyclen substituted with two l-tryptophan units, Zn(II)-Cyclen-(Trp)2 has been synthesized and evaluated for antiproliferative activity. Zn(II)-Cyclen-(Trp)2 was synthesized in ∼70% yield and its DNA binding potential was evaluated through QM/MM study which suggested good binding (G=-9.426) with B-DNA. The decrease in intensity of the positive and negative bands of CT-DNA at 278nm and 240nm, respectively demonstrated an effective unwinding of the DNA helix with loss of helicity. The complex was identified as an antiproliferative agent against U-87MG cells with 5 fold increase in apoptosis with respect to control (2h post incubation, IC50 25µM). Electrophoresis and comet assay studies exhibited an increase in DNA breakage after treatment with complex while caspase-3/ß-actin cleavage established a caspase-3 dependent apoptosis pathway in U-87 MG cells after triggering DNA damage. In vivo tumor specificity of the developed ligand was validated after radiocomplexation with 99mTc (>98% radiochemical yield and specific activity of 2.56GBq/µmol). Avid tumor/muscle ratio of >6 was depicted in biodistribution and SPECT imaging studies in U-87 MG xenograft model nude mice.

Metal based imaging probes of DO3A-Act-Met for LAT1 mediated methionine specific tumors: synthesis and preclinical evaluation.

PURPOSE: Tumor cells are known to have an elevated requirement for methionine due to increased protein synthesis and trans-methylation reactions. A methionine based macrocyclic tumor imaging system, DO3A-Act-Met, has been designed to provide a novel platform for tumor imaging via modalities, PET/MRI using metal ions, (68)Ga and (157)Gd. METHODS: Synthesis of DO3A-Act-Met was confirmed through NMR and mass spectrometric techniques. Cytotoxicity of complexes was evaluated using MTT assay whereas receptor binding and trans-stimulation studies were performed on EAT and U-87 MG cell lines. Tumor targeting was assessed through imaging and biodistribution experiments on U-87 MG xenograft model. RESULTS: DO3A-Act-Met was synthesized and radiolabeled with (68)Ga in high radiochemical purity (85-92%). The receptor binding assay on EAT cells predicted high binding affinity with Kd of 0.78 nM. Efflux of (35)S-L-methionine trans-stimulated by extracellular DO3A-Act-Met on U-87MG cells suggested an L-system transport. MR studies revealed a longitudinal relaxivity of 4.35 mM(-1) s(-1) for Gd-DO3A-Act-Met and a 25% signal enhancement at tumor site. The biodistribution studies in U-87MG xenografts validated tumor specificity. CONCLUSION: DO3A-Act-Met, a methionine conjugated probe is a promising agent for targeted molecular imaging, exhibiting high specificity towards tumor owing to its essential role in proliferation of cancer cells mediated through LAT1.

Preclinical evaluation of DO3A-Act-AQ: a polyazamacrocyclic monomeric anthraquinone derivative as a theranostic agent.

An anthraquinone conjugated macrocyclic chelating agent, 2,2',2″-(10-(2-(9,10-dioxo-9,10-dihydroanthracen-1-ylamino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid or DO3A-Act-AQ, was synthesized by reacting trisubstituted cyclen (DO3A) with 2-chloro-N-(9,10-dioxo-9,10-dihydro-anthracen-1-yl)-acetamide and radiolabeled with (68)GaCl3 in 84% efficiency and a specific activity of 4.62 MBq/nmol. The IC50 value for BMG-1 cells was 0.1 mM, while the same concentration of DO3A-Act-AQ rendered no significant toxicity in HEK cells. The exposure of BMG-1 cells with 0.1 mM DO3A-Act-AQ displayed a time-dependent increase in apoptosis (40.7% at 4 h and 53% at 24 h), and the effect was 2.8- and 3.6-fold % higher as seen in HEK cells. An increase in S-phase cell population suggested S-phase arrest concomitant with induction of apoptosis in BMG-1 cells reaching to 4.5 times after 24 h with respect to control cells. DNA binding studies on CT-DNA (calf thymus) revealed a quenching pattern in the presence of DO3A-Act-AQ (10-70 µM), and the Stern-Volmer quenching constant was 2.4157 × 10(6) L mol(-1), indicative of strong binding with ds-DNA. A decrease in the positive and negative bands of CT-DNA was seen at 278 nm and 240 nm, respectively, on addition of 0.05 mM of DO3A-Act-AQ in CD studies. (68)Ga-DO3A-Act-AQ was stable in vitro in both PBS and human serum for at least 2 h. The in vivo blood kinetics study performed on normal rabbits indicated fast clearance with t1/2(F) = 40 ± 0.3 min and t1/2(S) = 3 h 30 min ± 0.1 min. Ex vivo biodistribution analysis displayed a favorable tumor-to-muscle ratio of 8.4 after 2 h in athymic nude mice xenografted with BMG-1 cells, suggesting the specificity of (68)Ga-DO3A-Act-AQ toward tumors.

(68)Ga based probe for Alzheimer's disease: synthesis and preclinical evaluation of homodimeric chalcone in ß-amyloid imaging.

In an attempt to explore use of PET radioisotope, (68)Ga, in the diagnosis of Alzheimer's disease, a metal-based homodimeric ligand exhibiting high affinity towards Aß aggregates was designed by conjugating two chalcone units with the chelating system, diethylenetriaminepentaacetic acid. Bischalcone derivative, 5,8-bis(carboxymethyl)-13-(4-((E)-3-(4-(dimethylamino)phenyl)acryloyl)phenoxy)-2-(2-(2-(4-((E)-3-(4-(dimethylamino)phenyl)acryloyl)phenoxy)ethylamino)-2-oxoethyl)-10-oxo-2,5,8,11-tetraazatridecane-1-carboxylic acid, DT(Ch)2 was synthesized in 95% yield with high purity. It was radiolabelled with (68)Ga under mild conditions with 85.4% efficiency and 9.5-10 MBq nmol(-1) specific activity. An in vitro binding assay on Aß42 aggregates displayed high binding affinity of (68)Ga-DT(Ch)2 and inhibition constant of 4.18 ± 0.62 nM. The fluorescent properties of the ligand with peaks of absorption/emission at 410/540 nm exhibited a blue shift with 5.5-fold increase in emission intensity on binding with Aß aggregates. Blood kinetics of the complex performed on normal rabbit exhibited fast clearance (t1/2(F) = 24 ± 0.08 min; t1/2(S) = 2 h 40 ± 0.04 min). Ex vivo biodistribution analysis demonstrated blood-brain barrier penetration with brain uptake of 1.24 ± 0.31% ID g(-1) at 2 min p.i. and rapid washout with negligible activity (0.36% ID g(-1)) left at 30 min p.i. These preliminary studies reveal that the bivalent approach of synthesis had minimal effect on binding affinity, signifying that the developed (68)Ga-complex, (68)Ga-DT(Ch)2, may offer a new perspective in generator produced PET imaging probes for Alzheimer's disease.

Bioconjugation Techniques for Enhancing Stability and Targeting Efficiency of Protein and Peptide Therapeutics.

Bioconjugation techniques have emerged as powerful tools for enhancing the stability and targeting efficiency of protein and peptide therapeutics. This review provides a comprehensive analysis of the various bioconjugation strategies employed in the field. The introduction highlights the significance of bioconjugation techniques in addressing stability and targeting challenges associated with protein and peptide-based drugs. Chemical and enzymatic bioconjugation methods are discussed, along with crosslinking strategies for covalent attachment and site-specific conjugation approaches. The role of bioconjugation in improving stability profiles is explored, showcasing case studies that demonstrate successful stability enhancement. Furthermore, bioconjugation techniques for ligand attachment and targeting are presented, accompanied by examples of targeted protein and peptide therapeutics. The review also covers bioconjugation approaches for prolonging circulation and controlled release, focusing on strategies to extend half-life, reduce clearance, and design-controlled release systems. Analytical characterization techniques for bioconjugates, including the evaluation of conjugation efficiency, stability, and assessment of biological activity and targeting efficiency, are thoroughly examined. In vivo considerations and clinical applications of bioconjugated protein and peptide therapeutics, including pharmacokinetic and pharmacodynamic considerations, as well as preclinical and clinical developments, are discussed. Finally, the review concludes with an overview of future perspectives, emphasizing the potential for novel conjugation methods and advanced targeting strategies to further enhance the stability and targeting efficiency of protein and peptide therapeutics.

The 18-kDa Translocator Protein PET Tracers as a Diagnostic Marker for Neuroinflammation: Development and Current Standing.

Translocator protein (TSPO, 18 kDa) is an evolutionary, well-preserved, and tryptophan-rich 169-amino-acid protein which localizes on the contact sites between the outer and inner mitochondrial membranes of steroid-synthesizing cells. This mitochondrial protein is implicated in an extensive range of cellular activities, including steroid synthesis, cholesterol transport, apoptosis, mitochondrial respiration, and cell proliferation. The upregulation of TSPO is well documented in diverse disease conditions including neuroinflammation, cancer, brain injury, and inflammation in peripheral organs. On the basis of these outcomes, TSPO has been assumed to be a fascinating subcellular target for early stage imaging of the diseased state and for therapeutic purposes. The main outline of this Review is to give an update on dealing with the advances made in TSPO PET tracers for neuroinflammation, synchronously emphasizing the approaches applied for the design and advancement of new tracers with reference to their structure-activity relationship (SAR).

Cold Atmospheric Plasma as a Novel Therapeutic Tool for the Treatment of Brain Cancer.

BACKGROUND: Studies from the past few years revealed the importance of Cold Atmospheric Plasma (CAP) on various kinds of diseases, including brain cancers or glioblastoma (GBM), and hence coined a new term 'Plasma Medicine' in the modern world for promising therapeutic approaches. Here, we focus on the efficacy of CAP and its liquid derivatives on direct interactions or with specific nanoparticles to show pivotal roles in brain cancer treatment. METHOD: In the present review study, the authors studied several articles over the past decades published on the types of CAP and its effects on different brain cancers and therapy. RESULTS: A growing body of evidence indicates that CAP and its derivatives like Plasma Activated Media/ Water (PAM/PAW) are introduced in different kinds of GBM. Recent studies proposed that CAP plays a remarkable role in GBM treatment. To increase the efficacy of CAP, various nanoparticles of different origins got specific attention in recent times. In this review, different strategies to treat brain cancers, including nanoparticles, are discussed as enhancers of CAP induced targeted nanotherapeutic approach. CONCLUSION: CAP treatment and its synergistic effects with different nanoparticles hold great promise for clinical applications in early diagnosis and treatment of GBM treatment. However, results obtained from previous studies were still in the preliminary phase, and there must be a concern over the use of optimal methods for a dosage of CAP and nanoparticles for complete cure of GBM.

T-2 mycotoxin: toxicological effects and decontamination strategies.

Mycotoxins are highly diverse secondary metabolites produced in nature by a wide variety of fungus which causes food contamination, resulting in mycotoxicosis in animals and humans. In particular, trichothecenes mycotoxin produced by genus fusarium is agriculturally more important worldwide due to the potential health hazards they pose. It is mainly metabolized and eliminated after ingestion, yielding more than 20 metabolites with the hydroxy trichothecenes-2 toxin being the major metabolite. Trichothecene is hazardously intoxicating due to their additional potential to be topically absorbed, and their metabolites affect the gastrointestinal tract, skin, kidney, liver, and immune and hematopoietic progenitor cellular systems. Sensitivity to this type of toxin varying from dairy cattle to pigs, with the most sensitive endpoints being neural, reproductive, immunological and hematological effects. The mechanism of action mainly consists of the inhibition of protein synthesis and oxidative damage to cells followed by the disruption of nucleic acid synthesis and ensuing apoptosis. In this review, the possible hazards, historical significance, toxicokinetics, and the genotoxic and cytotoxic effects along with regulatory guidelines and recommendations pertaining to the trichothecene mycotoxin are discussed. Furthermore, various techniques utilized for toxin determination, pathophysiology, prophylaxis and treatment using herbal antioxidant compounds and regulatory guidelines and recommendations are reviewed. The prospects of the trichothecene as potential hazardous agents, decontamination strategies and future perspectives along with plausible therapeutic uses are comprehensively described.