Antisense oligodeoxynucleotides as a tool in developmental neuroendocrinology

Recent Advances in the Biomedical Applications of Functionalized Nanogels

Nanomaterials have been extensively used in several applications in the past few decades related to biomedicine and healthcare. Among them, nanogels (NGs) have emerged as an important nanoplatform with the properties of both hydrogels and nanoparticles for the controlled/sustained delivery of chemo drugs, nucleic acids, or other bioactive molecules for therapeutic or diagnostic purposes. In the recent past, significant research efforts have been invested in synthesizing NGs through various synthetic methodologies such as free radical polymerization, reversible addition-fragmentation chain-transfer method (RAFT) and atom transfer radical polymerization (ATRP), as well as emulsion techniques. With further polymeric functionalizations using activated esters, thiol-ene/yne processes, imines/oximes formation, cycloadditions, nucleophilic addition reactions of isocyanates, ring-opening, and multicomponent reactions were used to obtain functionalized NGs for targeted delivery of drug and other compounds. NGs are particularly intriguing for use in the areas of diagnosis, analytics, and biomedicine due to their nanodimensionality, material characteristics, physiological stability, tunable multi-functionality, and biocompatibility. Numerous NGs with a wide range of functionalities and various external/internal stimuli-responsive modalities have been possible with novel synthetic reliable methodologies. Such continuous development of innovative, intelligent materials with novel characteristics is crucial for nanomedicine for next-generation biomedical applications. This paper reviews the synthesis and various functionalization strategies of NGs with a focus on the recent advances in different biomedical applications of these surface modified/functionalized single-/dual-/multi-responsive NGs, with various active targeting moieties, in the fields of cancer theranostics, immunotherapy, antimicrobial/antiviral, antigen presentation for the vaccine, sensing, wound healing, thrombolysis, tissue engineering, and regenerative medicine.

Nanogels: An overview of properties, biomedical applications and obstacles to clinical translation

Nanogels have emerged as a versatile hydrophilic platform for encapsulation of guest molecules with a capability to respond to external stimuli that can be used for a multitude of applications. These are soft materials capable of holding small molecular therapeutics, biomacromolecules, and inorganic nanoparticles within their crosslinked networks, which allows them to find applications for therapy as well as imaging of a variety of disease conditions. Their stimuli-responsive behavior can be easily controlled by selection of constituent polymer and crosslinker components to achieve a desired response at the site of action, which imparts nanogels the ability to participate actively in the intended function of the carrier system rather than being passive carriers of their cargo. These properties not only enhance the functionality of the carrier system but also help in overcoming many of the challenges associated with the delivery of cargo molecules, and this review aims to highlight the distinct and unique capabilities of nanogels as carrier systems for the delivery of an array of cargo molecules over other nanomaterials. Despite their obvious usefulness, nanogels are still not a commonplace occurrence in clinical practice. We have also made an attempt to highlight some of the major challenges that need to be overcome to advance nanogels further in the field of biomedical applications.

Sexual dimorphism of cardiopulmonary regulation in the arcuate nucleus of the hypothalamus

The arcuate nucleus of the hypothalamus (ANH) interacts with other hypothalamic nuclei, forebrain regions, and downstream brain sites to affect autonomic nervous system outflow, energy balance, temperature regulation, sleep, arousal, neuroendocrine function, reproduction, and cardiopulmonary regulation. Compared to studies of other ANH functions, how the ANH regulates cardiopulmonary function is less understood. Importantly, the ANH exhibits structural and functional sexually dimorphic characteristics and contains numerous neuroactive substances and receptors including leptin, neuropeptide Y, glutamate, acetylcholine, endorphins, orexin, kisspeptin, insulin, Agouti-related protein, cocaine and amphetamine-regulated transcript, dopamine, somatostatin, components of renin-angiotensin system and gamma amino butyric acid that modulate physiological functions. Moreover, several clinically relevant disorders are associated with ANH ventilatory control dysfunction. This review highlights how ANH neurotransmitter systems and receptors modulate breathing differently in male and female rodents. Results highlight the significance of the ANH in cardiopulmonary regulation. The paucity of studies in this area that will hopefully spark investigations of sexually dimorphic ANH-modulation of breathing.

Gadd45b is an epigenetic regulator of juvenile social behavior and alters local pro-inflammatory cytokine production in the rodent amygdala

Precise regulation of the epigenome during perinatal development is critical to the formation of species-typical behavior later in life. Recent data suggests that Gadd45b facilitates active DNA demethylation by recruiting proteins involved in base excision repair (BER), which will catalyze substitution of 5-methyl-cytosine (5mC) for an unmodified cytosine. While a role for Gadd45b has been implicated in both hippocampal and amygdalar learning tasks, to the best of our knowledge, no study has been done investigating the involvement of Gadd45b in neurodevelopmental programming of social behavior. To address this, we used a targeted siRNA delivery approach to transiently knock down Gadd45b expression in the neonatal rat amygdala. We chose to examine social behavior in the juvenile period, as social deficits associated with neurodevelopmental disorders tend to emerge in humans at an equivalent age. We find that neonatal Gadd45b knock-down results in altered juvenile social behavior and reduced expression of several genes implicated in psychiatric disorders, including methyl-CpG-binding protein 2 (MeCP2), Reelin, and brain derived neurotrophic factor (BDNF). We furthermore report a novel role for Gadd45b in the programmed expression of α2-adrenoceptor (Adra2a). Consistent with Gadd45b's role in the periphery, we also observed changes in the expression of pro-inflammatory cytokines interleukin-6 (Il-6) and interleukin-1beta (Il-1beta) in the amygdala, which could potentially mediate or exacerbate effects of Gadd45b knockdown on the organization of social behavior. These data suggest a prominent role for Gadd45b in the epigenetic programming of complex juvenile social interactions, and may provide insight into the etiology of juvenile behavioral disorders such as ADHD, autism, and/or schizophrenia.

Antisense gene inhibition by phosphorothioate antisense oligonucleotide in Arabidopsis pollen tubes

Sexual reproduction is an essential biological event for proliferation of plants. The pollen tube (PT) that contained male gametes elongates and penetrates into the pistils for successful fertilization. However, the molecular mechanisms of plant fertilization remain largely unknown. Here, we report a transient inhibition of gene function using phosphorothioate antisense oligodeoxynucleotides (AS-ODNs) without cytofectin, which is a simple way to study gene function in Arabidopsis thaliana PTs. The PTs treated with AS-ODNs against both ANX1 and ANX2 showed short, knotted, and ruptured morphology in vitro/semi-in vitro, whereas normal PT growth was shown in its sense control in vitro/semi-in vitro. PT growth was impaired in a manner dependent on the dose of AS-ODNs against both ANX1 and ANX2 above 10 μm. The treatment with AS-ODNs against ROP1 and CalS5 resulted in waving PTs and in short PTs with a few callose plugs, respectively. The expression levels of the target genes in PTs treated with their AS-ODNs were lower than or similar to those in the sense control, indicating that the inhibition was directly or indirectly related to the expression of each mRNA. The AS-ODN against fluorescent protein (sGFP) led to reduced sGFP expression, suggesting that the AS-ODN suppressed protein expression. This method will enable the identification of reproductively important genes in Arabidopsis PTs.

Kinases SPAK and OSR1 are upregulated by estradiol and activate NKCC1 in the developing hypothalamus

In immature neurons the amino acid neurotransmitter, GABA provides the dominant mode for neuronal excitation by inducing membrane depolarization due to Cl(-) efflux through GABA(A) receptors (GABA(A)Rs). The driving force for Cl(-) is outward because the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) elevates the Cl(-) concentration in these cells. GABA-induced membrane depolarization and the resulting activation of voltage-gated Ca(2+) channels is fundamental to normal brain development, yet the mechanisms that regulate depolarizing GABA are not well understood. The neurosteroid estradiol potently augments depolarizing GABA action in the immature hypothalamus by enhancing the activity of the NKCC1 cotransporter. Understanding how estradiol controls NKCC1 activity will be essential for a complete understanding of brain development. We now report that estradiol treatment of newborn rat pups significantly increases protein levels of two kinases upstream of the NKCC1 cotransporter, SPAK (STE20/SPS1-related proline alanine rich kinase) and OSR1 (oxidative stress response kinase). The estradiol-induced increase is transcription dependent, and its time course parallels that of estradiol-enhanced phosphorylation of NKCC1. Antisense oligonucleotide-mediated knockdown of SPAK, and to a lesser degree of OSR1, precludes estradiol-mediated enhancement of NKCC1 phosphorylation. Functionally, knockdown of SPAK or OSR1 in embryonic hypothalamic cultures diminishes estradiol-enhanced Ca(2+) influx induced by GABA(A)R activation. Our data suggest that SPAK and OSR1 may be critical factors in the regulation of depolarizing GABA-mediated processes in the developing brain. It will be important to examine these kinases with respect to sex differences and developmental brain anomalies in future studies.

Microparticle-based delivery of oxytocin receptor antisense DNA in the medial amygdala blocks social recognition in female mice

Social recognition constitutes the basis of social life. In male mice and rats, social recognition is known to be governed by the neuropeptide oxytocin (OT) through its action on OT receptors (OTRs) in the medial amygdala. In female rats and mice, which have sociosexual behaviors controlling substantial investment in reproduction, an important role for OT in sociosexual behaviors has also been shown. However, the site in the female brain for OT action on social recognition is still unknown. Here we used a customized, controlled release system of biodegradable polymeric microparticles to deliver, in the medial amygdala of female mice, "locked nucleic acid" antisense (AS) oligonucleotides with sequences specific for the mRNA of the OTR gene. We found that single bilateral intraamygdala injections of OTR AS locked nucleic acid oligonucleotides several days before behavioral testing reduced social recognition. Thus, we showed that gene expression for OTR specifically in the amygdala is required for normal social recognition in female mice. Importantly, during the same experiment, we performed a detailed ethological analysis of mouse behavior revealing that OTR AS-treated mice underwent an initial increase in ambivalent risk-assessment behavior. Other behaviors were not affected, thus revealing specific roles for amygdala OTR in female social recognition potentially mediated by anxiety in a social context. Understanding the functional genomics of OT and OTR in social recognition should help elucidate the neurobiological bases of human disorders of social behavior (e.g., autism).

Estradiol-induced conditioned place preference may require actions at estrogen receptors in the nucleus accumbens

Intrinsic rewarding effects of estradiol (E(2)) may underlie some of the sex differences that emerge postpuberty for the prevalence of drug use and behavioral responses to drugs, but the effects and mechanisms of E(2) for reward have not been well characterized. Conditioned place preference (CPP), as measured by the time spent on the nonpreferred/drug-associated side of the chamber, was utilized as a functional assay to investigate the effects and mechanisms of E(2) in the nucleus accumbens for reward. To determine whether intracellular estrogen receptors (ERs) are important for E(2)-induced CPP, rats were administered E(2) (10 microg; subcutaneously (s.c.)), which produced CPP in each experiment, and/or ER blockers, such as tamoxifen (Experiment 1), ICI 182,780 (Experiment 2), or antisense oligonucleotides targeted to ERs (Experiment 3). Experiment 1: E(2) significantly increased the time spent on the originally nonpreferred side of the chamber. Coadministration of tamoxifen (10 mg/kg; s.c.) attenuated effects of E(2) to produce a CPP, but tamoxifen alone, increased time spent on the nonpreferred side. Experiment 2: coadministration of ICI 182,780 (10 microg/microl) to the nucleus accumbens attenuated effects of E(2) to enhance CPP and did not produce a CPP when administered alone. Experiment 3: coadministration of s.c. E(2) with ER antisense oligonucleotides to the nucleus accumbens significantly decreased time spent on the nonpreferred side and expression of ERs in the nucleus accumbens compared to scrambled antisense oligonucleotides or saline vehicle administration. Thus, E(2)'s rewarding effects may involve actions at ERs in the nucleus accumbens.

Targeting steroid receptor coactivator-1 expression with locked nucleic acids antisense reveals different thresholds for the hormonal regulation of male sexual behavior in relation to aromatase activity and protein expression

Steroid receptors such as the androgen and estrogen receptors require the presence of several proteins, known as coactivators, to enhance the transcription of target genes. The first goal of the present study was to define the role of SRC-1 on the steroid-dependent expression of the aromatase protein and its activity in male Japanese quail. The second goal was to analyze the rapid plasticity of the POM following antisense treatment interruption. We confirm here that the inhibition of SRC-1 expression by daily intracerebroventricular injections of locked nucleic acid antisense oligonucleotides in the third ventricle at the level of the preoptic area-hypothalamus (HPOA) significantly reduces testosterone-dependent male sexual behavior. In the first experiment, aromatase protein expression in HPOA was inhibited in SRC-1-depleted males but the enzymatic activity remained at the level measured in controls. We observed in the second experiment a recovery of the behavioral response to testosterone treatment after interruption of the antisense injection. However, several morphological characteristics of the POM were not different between the control group, the antisense-treated birds and antisense-treated birds in which treatment had been discontinued 3 days earlier. Antisense was also less effective in knocking-down SRC-1 in the present experiments as compared to our previous study. An analysis of this variation in the degree of knock-down of SRC-1 expression suggests dissociation among different aspects of steroid action on brain and behavior presumably resulting from the differential sensitivity of behavioral and neurochemical responses to the activation by testosterone and/or its estrogenic metabolites.

Nanogels for oligonucleotide delivery to the brain

Systemic delivery of oligonucleotides (ODN) to the central nervous system is needed for development of therapeutic and diagnostic modalities for treatment of neurodegenerative disorders. Macromolecules injected in blood are poorly transported across the blood-brain barrier (BBB) and rapidly cleared from circulation. In this work we propose a novel system for ODN delivery to the brain based on nanoscale network of cross-linked poly(ethylene glycol) and polyethylenimine ("nanogel"). The methods of synthesis of nanogel and its modification with specific targeting molecules are described. Nanogels can bind and encapsulate spontaneously negatively charged ODN, resulting in formation of stable aqueous dispersion of polyelectrolyte complex with particle sizes less than 100 nm. Using polarized monolayers of bovine brain microvessel endothelial cells as an in vitro model this study demonstrates that ODN incorporated in nanogel formulations can be effectively transported across the BBB. The transport efficacy is further increased when the surface of the nanogel is modified with transferrin or insulin. Importantly the ODN is transported across the brain microvessel cells through the transcellular pathway; after transport, ODN remains mostly incorporated in the nanogel and ODN displays little degradation compared to the free ODN. Using mouse model for biodistribution studies in vivo, this work demonstrated that as a result of incorporation into nanogel 1 h after intravenous injection the accumulation of a phosphorothioate ODN in the brain increases by over 15 fold while in liver and spleen decreases by 2-fold compared to the free ODN. Overall, this study suggests that nanogel is a promising system for delivery of ODN to the brain.

Lobotomy of genes: use of RNA interference in Neuroscience

Galen of Pergamon studied nerve function by shearing nerves in various species including monkeys, dogs, bulls and even elephants (humans being off limits to researchers; Sartan, 1954). An analogous strategy to determine gene function by ablating gene expression has recently been developed. RNA interference (RNAi) is a cellular response to double-stranded RNA (dsRNA) apparently as a defense against viral or transposon activity (Denli and Hannon, 2003; Dykxhoorn et al., 2003; Plasterk, 2002; Zamore, 2002). By activating this ancient defense mechanism through the introduction of artificial dsRNA, it is now possible to inhibit expression of almost any gene in almost any cell type, among them neuronal cells. In mammalian cells the active RNAi species must be short, approximately 21 nucleotide RNAs; these 21-bp species are called short interfering RNA (siRNA; Fig 1).

Reducing GABA receptors

A number of important drugs act on GABA(A) receptors, pentameric GABA-gated chloride channels assembled from among 19 known subunits. In trying to discover the roles in the brain of the subunits and their combinations, with the goal of developing more selective drugs, one tool has been to reduce expression of the subunits and examine the functional consequences. After briefly examining the properties of GABA(A) receptors, this review surveys the means available for receptor subunit reduction, and some of the observations to which their application has led. The methods discussed include radiation-induced deletion, gene knockout, knock-in mutations, antisense, ribozymes, RNA interference, dominant negative constructs, and transcriptional regulation, e.g., via decoy oligonucleotides.

Nuclear receptor coactivators modulate hormone-dependent gene expression in brain and female reproductive behavior in rats

Gonadal steroid hormones act in the brain to elicit changes in gene expression that result in profound effects on behavior and physiology. A variety of in vitro studies indicate that nuclear receptor coactivators are required for efficient transcriptional activity of steroid receptors. Two nuclear receptor coactivators, steroid receptor coactivator-1 (SRC-1) and cAMP response element binding protein-binding protein (CBP), have been shown to act in concert to enhance ER activity in vitro. In the present study, we investigated the function of these important nuclear receptor coactivators in estrogen action in rodent brain. Reduction of SRC-1 and CBP protein in brain disrupted ER-mediated activation of the behaviorally relevant progestin receptor gene. Furthermore, we found that SRC-1 and CBP function in brain to modulate the expression of hormone-dependent female sexual behavior. These findings indicate that these nuclear receptor coactivators function in brain to modulate ER transcriptional activity and the expression of hormone-dependent behavior.

Granulin precursor gene: a sex steroid-inducible gene involved in sexual differentiation of the rat brain

The mechanisms of sexual differentiation of the brain by sex steroids seem to be conserved throughout the mammalian species, although there may be some species differences. In rats, sex-dependent differentiation of the brain occurs in a sex steroid-dependent manner during the perinatal period known as the critical period. Androgen exposure during the perinatal period results in the development of structural and functional sexually dimorphic characteristics in the brain; the absence of testicular androgen leads the central nervous system to develop passively in a primarily female fashion, while the presence of androgen induces the masculinization of the brain. We attempted to characterize sex steroid-inducible genes that are involved in the sexually dimorphic function of the brain. Following the cDNA subtraction between hypothalami of 5-day-old intact and neonatally androgenized female rats, a granulin (grn) precursor gene was identified. The grn gene encodes a 6-kDa polypeptide known as a growth modulating factor of epithelial cells in vitro. Exogenous estrogen, as well as androgen, induced grn gene expression in the neonatal hypothalamus. In the brain of a 5-day-old male rat, grn mRNA was expressed in the ventromedial hypothalamic nucleus and the arcuate nucleus of the hypothalamus. Throughout the critical period for sexual differentiation of the brain, grn gene expression remained high in males, while in females it gradually decreased. Antisense oligodeoxynucleotide (ODN) complementary to grn mRNA was synthesized and infused into the third ventricle of male rats at 2 days of age. Two different control treatments were used; the first consisted of a control sequence ODN that had virtually no homology to known mRNAs, and the second consisted of vehicle alone. After maturation, the subject animals that were treated with antisense ODN of grn displayed significantly lower scores than the control males in various parameters assessing sexual behavior, i.e., mount, intromission, and ejaculation. The present results suggest that the grn gene, the expression of which is induced by sex steroids in the neonatal hypothalamus, plays a crucial role in the functional masculinization of the rat brain.