This study presents the design and evaluation of a series of multifunctional peptides and their gene delivery abilities. The peptide sequences contained a cell-penetrating segment, six continuous histidine residues, a stearyl moiety and a laminin receptor-targeting segment. The YIGSR segment promoted cellular uptake through the interaction with laminin receptors on the surface of cells, which resulted in a great improvement in gene transfection efficiency. The conformation, particle size and zeta potential of peptide/DNA complexes were characterized via circular dichroism and dynamic light scattering. Their gene transfection efficiency was investigated by fluorescence-activated cell sorting and confocal microscopy. The transfection efficiency of the designed peptide vectors was higher than that of Lipo 2000. The peptide TAT-H-K(C)-YIGSR displayed transfection efficiencies at N/P ratios of 6, which was 3.5 and 7 times higher than that of Lipo 2000 in B16F10 and 293T cells, respectively. All peptides exhibited lower cytotoxicity than Lipo 2000 in B16F10 and 293T cells. In summary, the designed YIGSR-containing multifunctional peptide gene vectors promoted cellular uptake and gene transfection. Their in vivo transfection ability was investigated in zebrafish, and the transfection efficiency was determined by confocal microscopy and bioluminescence imaging. The peptide vectors, owing to their relatively short sequences and ease of functionalization, offer a promising approach for gene delivery because of their low cytotoxicity and high transfection efficiency.

Human studies consistently identify bioenergetic maladaptations in brains upon aging and neurodegenerative disorders of aging (NDAs), such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and Amyotrophic lateral sclerosis. Glucose is the major brain fuel and glucose hypometabolism has been observed in brain regions vulnerable to aging and NDAs. Many neurodegenerative susceptible regions are in the topological central hub of the brain connectome, linked by densely interconnected long-range axons. Axons, key components of the connectome, have high metabolic needs to support neurotransmission and other essential activities. Long-range axons are particularly vulnerable to injury, neurotoxin exposure, protein stress, lysosomal dysfunction, etc. Axonopathy is often an early sign of neurodegeneration. Recent studies ascribe axonal maintenance failures to local bioenergetic dysregulation. With this review, we aim to stimulate research in exploring metabolically oriented neuroprotection strategies to enhance or normalize bioenergetics in NDA models. Here we start by summarizing evidence from human patients and animal models to reveal the correlation between glucose hypometabolism and connectomic disintegration upon aging/NDAs. To encourage mechanistic investigations on how axonal bioenergetic dysregulation occurs during aging/NDAs, we first review the current literature on axonal bioenergetics in distinct axonal subdomains: axon initial segments, myelinated axonal segments, and axonal arbors harboring pre-synaptic boutons. In each subdomain, we focus on the organization, activity-dependent regulation of the bioenergetic system, and external glial support. Second, we review the mechanisms regulating axonal nicotinamide adenine dinucleotide (NAD+) homeostasis, an essential molecule for energy metabolism processes, including NAD+ biosynthetic, recycling, and consuming pathways. Third, we highlight the innate metabolic vulnerability of the brain connectome and discuss its perturbation during aging and NDAs. As axonal bioenergetic deficits are developing into NDAs, especially in asymptomatic phase, they are likely exaggerated further by impaired NAD+ homeostasis, the high energetic cost of neural network hyperactivity, and glial pathology. Future research in interrogating the causal relationship between metabolic vulnerability, axonopathy, amyloid/tau pathology, and cognitive decline will provide fundamental knowledge for developing therapeutic interventions.

Successful gene therapy for brain tumors are often limited by two important factors, the existence of blood brain barrier (BBB) and inefficient transfection of brain tumor cells. In this study, we designed a series of peptide-based gene delivery vectors decorated with T7 segment for binding the transferrin (Tf) receptors which were highly expressed on brain tumor cells, and evaluated their ability of gene delivery. The physicochemical properties of peptide vectors or peptide/DNA complexes were studied as well. The in vitro transfection efficiency was investigated in normal and glioma cell lines. Among these complexes, PT-02/DNA complexes showed the highest transfection efficiency in glioma cells and low cytotoxicity in normal cell lines, and it could transport DNA across the BBB model in vitro . Furthermore, PT-02/DNA could deliver pIRES2-EGFP into the brain site of zebrafish in vivo . The designed peptide vectors offered a promising way for glioma gene therapy.

We designed a series of peptide vectors that contain functional fragments with the goal of enhancing cellular internalization and gene transfection efficiency. The functional fragments included a cellpenetrating peptide (R 9 ), a cationic amphiphilic a-helical peptide [(LLKK) 3 -H 6 or (LLHH) 3 ], a stearyl moiety, and cysteine residues. Vectors were also synthesized with D-type amino acids to improve their proteolytic stability. The conformations, particle sizes, and zeta potentials for complexes of these peptides with pGL3 plasmid DNA were characterized by circular dichroism and dynamic light scattering.In addition, cellular uptake of the peptide/DNA complexes and gene transfection efficiency were investigated with fluorescence-activated cell sorting and confocal laser-scanning microscopy. Greater transfection efficiency was achieved with the vectors containing the R 9 segment, and the efficiency was greater than Lipo2000. In addition, the D-type C 18 -c(llkk) 3 ch 6 -r 9 had about 7 times and 5.5 times the transfection efficiency of Lipo2000 in 293T cells and NIH-3T3 cells at the N/P ratio of 6, respectively. Overall, the multifunctional peptide gene vectors containing the R 9 segment exhibited enhanced cellular internalization, a high gene transfection efficiency, and low cytotoxicity.

Axonal transport, an ATP demanding process, plays a critical role in maintaining axonal and neuronal health. ATP in neurons is synthesized by glycolysis and mitochondrial respiration, both driven by proper NAD+/NADH redox potentials. NMNAT2 is the major neuronal NAD+ synthesizing enzyme and is a key axonal maintenance factor. Here, we show that NMNAT2 co-migrates with fast vesicular cargos in axons and is required for fast axonal transport in the distal axons of cortical neurons. Using SoNar sensor imaging to detect axonal NAD+ and NADH, we show that NMNAT2 is critical in maintaining NAD+/NADH potentials in distal axons. With Syn-ATP sensor imaging to detect synaptic vesicle ATP levels (sv-ATP), we demonstrate that glycolysis is the major provider of sv-ATP and NMNAT2 deletion significantly reduces sv-ATP levels. NAD+ supplementation to NMNAT2 KO neurons restores sv-ATP levels and fast axonal transports in a glycolysis-dependent manner. Together, these data show that NMNAT2 maintains the local NAD+/NADH redox potential and sustains on-board glycolysis to meet the bioenergetic demands of fast vesicular transport in distal axons. Intriguingly, mitochondrial respiration contributes significantly to sv-ATP levels in NMNAT2 KO axons. This finding suggests that NMNAT2 deletion induces metabolic plasticity by engaging mitochondria. Surprisingly, supplying NMN, the substrate for NMNAT2 in NAD+ synthesis, restores sv-ATP and axonal transport in NMNAT2 KO axons with an efficacy similar to NAD+. The restoration of NMNAT2 KO distal axonal sv-ATP levels and vesicle transport by NMN requires mitochondrial respiration, while the rescue by NAD+ is independent of mitochondrial respiration. Based on these findings, we hypothesize that NMN rescues glycolysis to restore axonal transport in NMNAT2 KO axons by taking advantage of the compensatory ATP-generating metabolic pathways triggered by NMNAT2 loss.