Is there evidence for using ketamine among individuals with dementia?

The aim of this short narrative review was to evaluate the existing literature regarding the clinical use of ketamine among individuals with dementia, especially those with behavioral disturbances. PubMed, Cochrane, and Ovid (Embase, APA PsycINFO, and MEDLINE) databases were searched for abstracts using the search terms "ketamine" AND "dementia." Only articles describing the use of ketamine in individuals with dementia were included. Articles that did not include individuals with dementia, did not use ketamine, were published in a non-English language, primarily described animal studies, or were reviews were excluded. Three case reports met the inclusion criteria. One described the use of subcutaneous ketamine for depression, one described the use of intramuscular ketamine for acute agitation, and one described the use of S-ketamine as anesthesia during electroconvulsive therapy for depression and catatonia. No significant adverse effects were reported in any of the cases. Although the use of ketamine in the treatment of depression and agitation associated with dementia has potential, the current evidence remains limited. High-quality prospective studies are needed to confirm the observations of these case reports before ketamine can be used to treat behavioral disturbances in individuals with dementia.

JAK3 mutations and mitochondrial apoptosis resistance in T-cell acute lymphoblastic leukemia.

Resistance to mitochondrial apoptosis predicts inferior treatment outcomes in patients with diverse tumor types, including T-cell acute lymphoblastic leukemia (T-ALL). However, the genetic basis for variability in this mitochondrial apoptotic phenotype is poorly understood, preventing its rational therapeutic targeting. Using BH3 profiling and exon sequencing analysis of childhood T-ALL clinical specimens, we found that mitochondrial apoptosis resistance was most strongly associated with activating mutations of JAK3. Mutant JAK3 directly repressed apoptosis in leukemia cells, because its inhibition with mechanistically distinct pharmacologic inhibitors resulted in reversal of mitochondrial apoptotic blockade. Inhibition of JAK3 led to loss of MEK, ERK and BCL2 phosphorylation, and BH3 profiling revealed that JAK3-mutant primary T-ALL patient samples were characterized by a dependence on BCL2. Treatment of JAK3-mutant T-ALL cells with the JAK3 inhibitor tofacitinib in combination with a spectrum of conventional chemotherapeutics revealed synergy with glucocorticoids, in vitro and in vivo. These findings thus provide key insights into the molecular genetics of mitochondrial apoptosis resistance in childhood T-ALL, and a compelling rationale for a clinical trial of JAK3 inhibitors in combination with glucocorticoids for patients with JAK3-mutant T-ALL.

Hedgehog pathway mutations drive oncogenic transformation in high-risk T-cell acute lymphoblastic leukemia.

The role of Hedgehog signaling in normal and malignant T-cell development is controversial. Recently, Hedgehog pathway mutations have been described in T-ALL, but whether mutational activation of Hedgehog signaling drives T-cell transformation is unknown, hindering the rationale for therapeutic intervention. Here, we show that Hedgehog pathway mutations predict chemotherapy resistance in human T-ALL, and drive oncogenic transformation in a zebrafish model of the disease. We found Hedgehog pathway mutations in 16% of 109 childhood T-ALL cases, most commonly affecting its negative regulator PTCH1. Hedgehog mutations were associated with resistance to induction chemotherapy (P = 0.009). Transduction of wild-type PTCH1 into PTCH1-mutant T-ALL cells induced apoptosis (P = 0.005), a phenotype that was reversed by downstream Hedgehog pathway activation (P = 0.007). Transduction of most mutant PTCH1, SUFU, and GLI alleles into mammalian cells induced aberrant regulation of Hedgehog signaling, indicating that these mutations are pathogenic. Using a CRISPR/Cas9 system for lineage-restricted gene disruption in transgenic zebrafish, we found that ptch1 mutations accelerated the onset of notch1-induced T-ALL (P = 0.0001), and pharmacologic Hedgehog pathway inhibition had therapeutic activity. Thus, Hedgehog-activating mutations are driver oncogenic alterations in high-risk T-ALL, providing a molecular rationale for targeted therapy in this disease.

Cellular Uptake of A Taurine-Modified, Ester Bond-Decorated D-Peptide Derivative via Dynamin-Based Endocytosis and Macropinocytosis.

Most of the peptides used for promoting cellular uptake bear positive charges. In our previous study, we reported an example of taurine (bearing negative charges in physiological conditions) promoting cellular uptake of D-peptides. Taurine, conjugated to a small D-peptide via an ester bond, promotes the cellular uptake of this D-peptide. Particularly, intracellular carboxylesterase (CES) instructs the D-peptide to self-assemble and to form nanofibers, which largely disfavors efflux and further enhances the intracellular accumulation of the D-peptide, as supported by that the addition of CES inhibitors partially impaired cellular uptake of this molecule in mammalian cell lines. Using dynamin 1, 2, and 3 triple knockout (TKO) mouse fibroblasts, we demonstrated that cells took up this molecule via macropinocytosis and dynamin-dependent endocytosis. Imaging of Drosophila larval blood cells derived from endocytic mutants confirmed the involvement of multiple endocytosis pathways. Electron microscopy (EM) indicated that the precursors can form aggregates on the cell surface to facilitate the cellular uptake via macropinocytosis. EM also revealed significantly increased numbers of vesicles in the cytosol. This work provides new insights into the cellular uptake of taurine derivative for intracellular delivery and self-assembly of D-peptides.

Enzymatic self-assembly of an immunoreceptor tyrosine-based inhibitory motif (ITIM).

Here we show the first example of an immunoreceptor tyrosine-based inhibitory motif (ITIM), LYYYYL, as well as its enantiomeric or retro-inverso peptide, to self-assemble in water via enzyme-instructed self-assembly. Upon enzymatic dephosphorylation, the phosphohexapeptides become hexapeptides, which self-assemble in water to result in supramolecular hydrogels. This work illustrates a new approach to design bioinspired soft materials from a less explored, but important pool of immunomodulatory peptides.

Enzyme-Instructed Self-Assembly of Peptides Containing Phosphoserine to Form Supramolecular Hydrogels as Potential Soft Biomaterials.

Enzyme-instructed self-assembly (EISA) offers a facile approach to explore the supramolecular assemblies of small molecules in cellular milieu for a variety of biomedical applications. One of the commonly used enzymes is phosphatase, but the study of the substrates of phosphatases mainly focuses on the phosphotyrosine containing peptides. In this work, we examine the EISA of phosphoserine containing small peptides for the first time by designing and synthesizing a series of precursors containing only phosphoserine or both phosphoserine and phosphotyrosine. Conjugating a phosphoserine to the C-terminal of a well-established self-assembling peptide backbone, (naphthalene-2-ly)-acetyl-diphenylalanine (NapFF), affords a novel hydrogelation precursor for EISA. The incorporation of phosphotyrosine, another substrate of phosphatase, into the resulting precursor, provides one more enzymatic trigger on a single molecule, and meanwhile increases the precursors' propensity to aggregate after being fully dephosphorylated. Exchanging the positions of phosphorylated serine and tyrosine in the peptide backbone provides insights on how the specific molecular structures influence self-assembling behaviors of small peptides and the subsequent cellular responses. Moreover, the utilization of D-amino acids largely enhances the biostability of the peptides, thus providing a unique soft material for potential biomedical applications.

Enzyme-Instructed Self-Assembly of Small D-Peptides as a Multiple-Step Process for Selectively Killing Cancer Cells.

Selective inhibition of cancer cells remains a challenge in chemotherapy. Here we report the molecular and cellular validation of enzyme-instructed self-assembly (EISA) as a multiple step process for selectively killing cancer cells that overexpress alkaline phosphatases (ALPs). We design and synthesize two kinds of D-tetrapeptide containing one or two phosphotyrosine residues and with the N-terminal capped by a naphthyl group. Upon enzymatic dephosphorylation, these D-tetrapeptides turn into self-assembling molecules to form nanofibers in water. Incubating these D-tetrapeptides with several cancer cell lines and one normal cell line, the unphosphorylated D-tetrapeptides are innocuous to all the cell lines, the mono- and diphosphorylated D-tetrapeptides selectively inhibit the cancer cells, but not the normal cell. The monophosphorylated D-tetrapeptides exhibit more potent inhibitory activity than the diphosphorylated D-tetrapeptides do; the cancer cell lines express higher level of ALPs are more susceptible to inhibition by the phosphorylated D-tetrapeptides; the precursors of D-tetrapeptides that possess higher self-assembling abilities exhibit higher inhibitory activities. These results confirm the important role of enzymatic reaction and self-assembly. Using uncompetitive inhibitors of ALPs and fluorescent D-tetrapeptides, we delineate that the enzyme catalyzed dephosphorylation and the self-assembly steps, together, result in the localization of the nanofibers of D-tetrapeptides for killing the cancer cells. We find that the cell death modality likely associates with the cell type and prove the interactions between nanofibers and the death receptors. This work illustrates a paradigm-shifting and biomimetic approach and contributes useful molecular insights for the development of spatiotemporal defined supramolecular processes/assemblies as potential anticancer therapeutics.

Taurine Boosts Cellular Uptake of Small D-Peptides for Enzyme-Instructed Intracellular Molecular Self-Assembly.

Due to their biostability, D-peptides are emerging as an important molecular platform for biomedical applications. Being proteolytically resistant, D-peptides lack interactions with endogenous transporters and hardly enter cells. Here we show that taurine, a natural amino acid, drastically boosts the cellular uptake of small D-peptides in mammalian cells by >10-fold, from 118 µM (without conjugating taurine) to >1.6 mM (after conjugating taurine). The uptake of a large amount of the ester conjugate of taurine and D-peptide allows intracellular esterase to trigger intracellular self-assembly of the D-peptide derivative, further enhancing their cellular accumulation. The study on the mechanism of the uptake reveals that the conjugates enter cells via both dynamin-dependent endocytosis and macropinocytosis, but likely not relying on taurine transporters. Differing fundamentally from the positively charged cell-penetrating peptides, the biocompatibility, stability, and simplicity of the enzyme-cleavable taurine motif promise new ways to promote the uptake of bioactive molecules for countering the action of efflux pump and contributing to intracellular molecular self-assembly.