Hernán Cortés

Nanoparticle technology for treatment of Parkinson's disease: the role of surface phenomena in reaching the brain.

The absence of a definitive treatment for Parkinsons disease has driven the emerging investigation in the search for novel therapeutic alternatives. At present, the formulation of different drugs on nanoparticles has represented several advantages over conventional treatments. This type of multifunctional carrier, owing to its size and composition, has different interactions in biological systems that can lead to a decrease in ability to cross the blood-brain barrier. Therefore, this review focuses on the latest advances in obtaining nanoparticles for Parkinsons disease and provides an overview of technical aspects in the design of brain drug delivery of nanoparticles and an analysis of surface phenomena, a key aspect in the development of functional nanoparticles for Parkinsons disease.

Presynaptic CaMKIIα modulates dopamine D3 receptor activation in striatonigral terminals of the rat brain in a Ca2+ dependent manner

CaMKIIα is expressed at high density in the nucleus accumbens where it binds to postsynaptic D3 receptors inhibiting their effects. In striatonigral projections, activation of presynaptic D3 receptors potentiates D1 receptor-induced stimulation of cAMP production and GABA release. In this study we examined whether the presynaptic effects of D3 receptor stimulation in the substantia nigra reticulata (SNr) are modulated by Ca²⁺ activation of CaMKIIα. In SNr synaptosomes two procedures that increase cytoplasmic Ca²⁺, ionomycin and K⁺-depolarization, blocked the additional stimulation of cAMP accumulation produced by coactivating D3 and D1 dopamine receptors. The selective CaMKIIα inhibitor KN-62 reversed the blockade produced by ionomycin and K⁺-depolarization. Incubation in either Ca²-free solutions or with the selective Ca²⁺ blocker nifedipine, also reversed the blocking effects of K⁺-depolarization. Immunoblot studies showed that K⁺-depolarization increased CaMKIIα phosphorylation in a KN-62 sensitive manner and promoted CaMKIIα binding to D3 receptors. In K⁺-depolarized tissues, D3 receptors potentiated D1 receptor-induced stimulation of [³H]GABA release only when CaMKIIα was blocked with KN-62. In the presence of this inhibitor, the selective D3 agonist PD 128,907 reduced the ED₅₀ for the D1 agonist SKF 38393 from 56 to 4 nM. KN-62 also enhanced the effects of dopamine on depolarization induced [³H]GABA release. KN-62 changed ED₅₀ for dopamine from 584 to 56 nM. KN-62 did not affect D1 and D4 receptor responses. These experiments show that in striatonigral projections, CaMKIIα inhibits the action of D3 receptors in a Ca²⁺ dependent manner blocking their modulatory effects on GABA release. These findings suggest a mechanism through which the frequency of action potential discharge in presynaptic terminals regulates dopamine effects.

GABAB receptors modulate depolarization-stimulated [3H]glutamate release in slices of the pars reticulata of the rat substantia nigra

GABA(B) receptors decrease the release of GABA from the striatal terminals within the pars reticulata of the substantia nigra by opposing the increase in the release caused by dopamine D₁ receptors. The dopamine D₁ receptors also increase the release of glutamate from subthalamic terminals in the pars reticulata. Because GABA(B) receptors decrease the glutamate release from these terminals, we have explored if the effect of GABA(B) receptors also opposed the effect of the dopamine D₁ receptors. The effect of baclofen, a selective GABA(B)-receptor agonist, was tested on the release of [³H]glutamate caused by highly (40 mM) concentrated K(+) solutions in slices of the pars reticulata. Baclofen decreased (the concentration causing 50% inhibition, IC₅₀, was 8.15 μM) the increase in the release of the [³H]glutamate caused by the dopamine D₁ receptors and it also decreased (IC₅₀ was 0.51 μM) this release in the absence of the activation of the dopamine D₁ receptors. The GABA(B) receptors appear then to inhibit glutamate release in two ways; one dependent on the activation of the dopamine D₁ receptors and the other independent of such activation. The protein kinase A-inhibitor H89 blocked the increase in the release of the [³H]glutamate caused by the dopamine D₁ receptors, though it did not block the dopamine D₁ receptor-independent baclofen inhibition of the release. This finding indicates that this inhibition was not via the protein kinase A signal-transduction pathway. N-ethylmaleimide, an alkylating agent that inactivates pertussis toxin-sensitive Gi proteins, eliminated both the dopamine D₁ receptor-dependent and -independent baclofen inhibition, showing that both were mediated by these proteins. The injection of baclofen into the pars reticulata of unanesthetized rats caused contralateral rotation, suggesting a reduced glutamate release from the subthalamic terminals, thereby stopping the inhibition of the premotor thalamic nuclei, causing locomotion. Our data suggest that GABA(B) receptors restrain the excitatory input from the subthalamic nucleus and stimulate motor behavior.

Dopaminergic denervation switches dopamine D3 receptor signaling and disrupts its Ca2 + dependent modulation by CaMKII and calmodulin in striatonigral projections of the rat

In striatonigral projections activation of dopamine D3 receptors (D3Rs) potentiates the stimulation of GABA release and cAMP production caused by activation of dopamine D1 receptors (D1Rs). Cytoplasmic [Ca(2+)] in the terminals controls this response by modulating CaMKII, an enzyme that depresses D3R action. To examine the effects of dopamine deprivation on D3R signaling we investigated their function in striatonigral terminals of hemiparkinsonian rats. Denervation switched the signaling cascade initiated by D3R activation. In the non-lesioned side activation of D3R potentiated the stimulatory effects of D1R activation on cAMP production and K(+)-depolarization induced [(3)H] GABA release. In contrast, in the denervated side the stimulatory effects of both D1R activation and forskolin administration were blocked by D3R activation. In non-lesioned slices, D3R responses were inhibited by the activation of CaMKII produced by K(+)-depolarization (via increased Ca(2+) entry). The CaMKII-induced inhibition was blocked by the selective inhibitor KN-62. In denervated tissues the response to D3R stimulation was not modified either by K(+) depolarization or by blocking CaMKII with KN-62. Immunoblotting studies showed that depolarization-induced CaMKII binding to the D3 receptor and CaMKII phosphorylation were suppressed in denervated tissues. We also determined calmodulin expression with PCR and immunoblot techniques. Both techniques showed that calmodulin expression was depressed in the lesioned side. In sum, our studies show that dopaminergic denervation switches the D3R signaling cascade and depresses CaMKII signaling through a process that appears to involve reduced calmodulin levels. Since calmodulin is a major cytoplasmic Ca(2+) buffer our findings suggest that abnormal Ca(2+) buffering may be an important component of the abnormalities observed during dopaminergic denervation.

Presynaptic cannabinoid CB2 receptors modulate [3H]-Glutamate release at subthalamo-nigral terminals of the rat

Recent studies suggested the expression of CB2 receptors in neurons of the CNS, however, most of these studies have only explored one aspect of the receptors, i.e., expression of protein, messenger RNA, or functional response, and more complete studies appear to be needed to establish adequately their role in the neuronal function. Electron microscopy studies showed the presence of CB2r in asymmetric terminals of the substantia nigra pars reticulata (SNr), and its mRNA appeared is expressed in the subthalamic nucleus. Here, we explore the expression, source, and functional effects of such receptors by different experimental approaches. Through PCR and immunochemistry, we showed mRNA and protein for CB2rs in slices and primary neuronal cultures from subthalamus. GW833972A, GW405833, and JHW 133, three CB2r agonists dose‐dependent inhibited K+‐induced [3H]‐Glutamate release in slices of SNr, and the two antagonist/inverse agonists, JTE‐907 and AM630, but not AM281, a CB1r antagonist, prevented GW833972A effect. Subthalamus lesions with kainic acid prevented GW833972A inhibition on release and decreased CB2r protein in nigral synaptosomes, thus nigral CB2rs originate in subthalamus. Inhibition of [3H]‐Glutamate release was PTX‐ and gallein‐sensitive, suggesting a Giβγ‐mediated effect. P/Q Ca2+‐type channel blocker, ω‐Agatoxin‐TK, also inhibited the [3H]‐Glutamate release, this effect was occluded with GW833972A inhibition, indicating that the βγ subunit effect is exerted on Ca2+channel activity. Finally, microinjections of GW833972A in SNr induced contralateral turning. Our data showed that presynaptic CB2rs inhibit [3H]‐Glutamate release in subthalamo‐nigral terminals by P/Q‐channels modulation through the Giβγ subunit and suggested their participation in motor behavior.

Comprehensive mapping of human body skin hydration: A pilot study

Previous studies analyzed a series of representative anatomical regions in the human body; however, there is a wide structural and cellular variability in the constitution of the skin. Our objective was to perform a comprehensive assessment of human skin hydration throughout the largest possible area.

From traditional biochemical signals to molecular markers for detection of sepsis after burn injuries

Sepsis is a life-threatening organ-dysfunction condition caused by a dysregulated response to an infectious condition that can cause complications in patients with major trauma. Burns are one of the most destructive forms of trauma; despite the improvements in medical care, infections remain an important cause of burn injury-related mortality and morbidity, and complicated sepsis predisposes patients to diverse complications such as organ failure, lengthening of hospital stays, and increased costs. Accurate diagnosis and early treatment of sepsis may have a beneficial impact on clinical outcome of burn-injured patients. In this review, we offer a comprehensive description of the current and traditional markers used as indicative of sepsis in burned patients. However, although these are markers of the inflammatory post-burn response, they usually fail to predict sepsis in severely burned patients due to that they do not reflect the severity of the infection. Identification and measurement of biomarkers in early stages of infection is important in order to provide timely response and effective treatment of burned patients. Therefore, we compiled important experimental evidence, demonstrating novel biomarkers, including molecular markers such as genomic DNA variations, alterations of transcriptome profiling (mRNA, miRNAs, lncRNAs and circRNAs), epigenetic markers, and advances in proteomics and metabolomics. Finally, this review summarizes next-generation technologies for the identification of markers for detection of sepsis after burn injuries.

Presynaptic Dopamine D2 Receptors Modulate [ 3 H]GABA Release at StriatoPallidal Terminals via Activation of PLC → IP3 → Calcineurin and Inhibition of AC → cAMP → PKA Signaling Cascades

Striatal dopamine D2 receptors activate the PLC → IP3 → Calcineurin-signaling pathway to modulate the neural excitability of En+ Medium-sized Spiny GABAergic neurons (MSN) through the regulation of L-type Ca2+ channels. Presynaptic dopaminergic D2 receptors modulate GABA release at striatopallidal terminals through L-type Ca2+ channels as well, but their signaling pathway is still undetermined. Since D2 receptors are Gi/o-coupled and negatively modulate adenylyl cyclase (AC), we investigated whether presynaptic D2 receptors modulate GABA release through the same signaling cascade that controls excitability in the striatum or by the inhibition of AC and decreased PKA activity. Activation of D2 receptors stimulated formation of [3H]IP1 and decreased Forskolin-stimulated [3H]cAMP accumulation in synaptosomes from rat Globus Pallidus. D2 receptor activation with Quinpirole in the presence of L 745,870 decreased, in a dose-dependent manner, K+-induced [3H]GABA release in pallidal slices. The effect was prevented by the pharmacological blockade of Gi/o βγ subunit effects with Gallein, PLC with U 73122, IP3 receptor activation with 4-APB, Calcineurin with FK506. In addition, when release was stimulated with Forskolin to activate AC, D2 receptors also decreased K+-induced [3H]GABA release, an effect occluded with the effect of the blockade of PKA with H89 or stimulation of release with the cAMP analog 8-Br-cAMP. These data indicate that D2 receptors modulate [3H]GABA release at striatopallidal terminals by activating the PLC → IP3 → Calcineurin-signaling cascade, the same one that modulates excitability in soma. Additionally, D2 receptors inhibit release when AC is active. Both mechanisms appear to converge to regulate the activity of presynaptic L-type Ca2+ channels.

Nanotechnology As Potential Tool for siRNA Delivery in Parkinson's Disease

BACKGROUND The lack of an outright treatment for Parkinsons disease (PD) is a pivotal concern in medicine and has driven the search for novel alternatives for treating the disease. Among the proposed approaches, small interfering RNA (siRNA)-based therapy is attracting significant attention as a potential method for the treatment of PD; however, siRNAs delivery possesses potential drawbacks, such as reduced stability in blood circulation and low capacity for reaching the target site. OBJECTIVE This review aims to explore siRNA-based approaches to PD and the latest advances for designing nanoparticles that effectively target siRNAs to the action site and that protect these against degradation in blood circulation. RESULTS siRNA-based approaches provide an interesting option for designing new strategies for treating PD through the silencing of genes, whose abnormal expressions contribute to the pathophysiology of the disease; however, siRNA delivery to the brain is a key issue that remains unsolved to date. Current research efforts are focused on designing vectors that effectively transport and protect siRNAs. In this regard, nanoparticles are being developed as carriers for siRNAs with controlled delivery efficiency and low toxicity profiles, and these represent an alternative to common vectors. CONCLUSION Identification of putative gene targets for siRNA therapy of PD has set the pace for researching non-viral vectors; however, the technological aspects for tackling the challenge that siRNAs targeting to the brain represents are essentials. In this respect, the formulation of siRNAs in nanoparticles would avoid harmful side effects, such as immunogenic and oncogenic drawbacks.