The Hypotonic Environmental Changes Affect Liposomal Formulations for Nose-to-Brain Targeted Drug Delivery

Systemic administration of drugs is ineffective in the treatment of central nervous system disorders because of the blood-brain barrier. Nasal administration has been suggested as an alternative administration route as drugs absorbed in the olfactory epithelium bypass the blood-brain barrier and reach the brain within minutes. However, the nasal mucosa properties (e.g., tonicity, pH) are not constant because of physiological and environmental factors, and this might limit the therapeutic outcome of nanocarrier-based formulations. To shine light on the impact of environmental ionic strength on nanocarrier-based formulations, we have studied how liposomal formulations respond to the change of tonicity of the external environment. Large unilamellar vesicles loaded with 6 different drugs were exposed to different hypotonic environments, creating an osmotic gradient within the inner core and external environment of the liposomes up to 650 mOsm/kg. Both size and polydispersity of liposomes were significantly affected by tonicity changes. Moreover, the release kinetics of hydrophilic and lipophilic drugs were largely enhanced by hypotonic environments. These results clearly demonstrate that the environmental ionic strength has an impact on liposomal formulation stability and drug release kinetics and it should be considered when liposomal formulations for nose-to-brain targeted drug delivery are designed.     

Functional map of arrestin-1 at single amino acid resolution

Arrestins function as adapter proteins that mediate G protein-coupled receptor (GPCR) desensitization, internalization, and additional rounds of signaling. Here we have compared binding of the GPCR rhodopsin to 403 mutants of arrestin-1 covering its complete sequence. This comprehensive and unbiased mutagenesis approach provides a functional dimension to the crystal structures of inactive, preactivated p44 and phosphopeptide-bound arrestins and will guide our understanding of arrestin–GPCR complexes. The presented functional map quantitatively connects critical interactions in the polar core and along the C tail of arrestin. A series of amino acids (Phe375, Phe377, Phe380, and Arg382) anchor the C tail in a position that blocks binding of the receptor. Interaction of phosphates in the rhodopsin C terminus with Arg29 controls a C-tail exchange mechanism in which the C tail of arrestin is released and exposes several charged amino acids (Lys14, Lys15, Arg18, Lys20, Lys110, and Lys300) for binding of the phosphorylated receptor C terminus. In addition to this arrestin phosphosensor, our data reveal several patches of amino acids in the finger (Gln69 and Asp73–Met75) and the lariat loops (L249–S252 and Y254) that can act as direct binding interfaces. A stretch of amino acids at the edge of the C domain (Trp194–Ser199, Gly337–Gly340, Thr343, and Thr345) could act as membrane anchor, binding interface for a second rhodopsin, or rearrange closer to the central loops upon complex formation. We discuss these interfaces in the context of experimentally guided docking between the crystal structures of arrestin and light-activated rhodopsin.The human genome encodes more than 800 G protein-coupled receptors (GPCRs), which mediate signaling between cells and provide an important link to our environment as the principal receptors for taste, smell, and vision. The visual system with its photoreceptor rhodopsin is an excellent system to understand GPCR signaling, as detailed information exists on the structures and dynamic interactions of the protein constituents (1). G protein-mediated signaling by light-activated rhodopsin is terminated by a process that begins with the phosphorylation of rhodopsin’s C terminus by the rhodopsin kinase GRK1. The phosphorylated, light-activated rhodopsin binds then to arrestin-1, which stops signaling by occluding the G protein-binding site. Further cloning efforts yielded two ubiquitously expressed nonvisual arrestins (arrestin-2 and arrestin-3 or β-arrestin-1 and β-arrestin-2) and the cone-specific arrestin-4. It seems clear today that most GPCRs share a common mechanism of signal termination involving receptor phosphorylation and the binding of arrestins. Arrestin-bound receptors may be internalized and degraded, internalized and recycled, and/or initiate G protein-independent signaling (2).In recent years there has been tremendous progress in the structure determination of active GPCR states including those of light-activated rhodopsin (3–5) and the first GPCR-G protein complex (6). Detailed structural information on the inactive state of arrestin-1 has been available for some time (7, 8). These inactive structures have recently been complemented with structures of a preactivated state of the arrestin-1 splice variant p44 (9) and of arrestin-2 bound to a receptor phosphopeptide (10). Analysis of these 3D structures provides many clues of how arrestins function. However, structures alone do not tell the whole story, as they contain little information about which subset of residues stabilize a particular conformation or contribute to receptor binding. The approximate binding surface was established by peptide (11) and antibody (12) competition experiments. Series of targeted mutagenesis studies based on the cell-free expression of radiolabeled arrestin (13) were used to probe the function of specific arrestin regions. However, these targeted studies are difficult to compare quantitatively as they have been gathered in over 20 y of work. Here we present an unbiased and complete scan of the arrestin-1 sequence to compare the relative impact of each amino acid on binding to light-activated, phosphorylated rhodopsin. These data provide a functional dimension to the available crystal structures and will guide our molecular understanding of GPCR–arrestin interactions.     

Effect of occlusal splint on interleukin 6, malondialdehyde and 8-hydroxydeoxyguanosine levels in the synovial fluid of patients with temporomandibular disorders

The actual role of splint therapy in preventing excessive loading of the temporomandibular joint (TMJ) is still debated. Lower intra-articular pressure levels have been measured in patients wearing occlusal splints, which may also reduce oxidative stress in the articular spaces. The aim of this study was to determine whether splint therapy reduces oxidative stress and inflammation in TMJ internal derangement patients by measuring interleukin 6 (IL-6), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) levels in the synovial fluid (SF). Twenty-four patients with a temporomandibular disorder (TMD) were included in the study. TMJ SF samples were obtained prior to arthrocentesis. Twelve patients used a 2-mm hard acrylic, maxillary stabilization-type splint for 3 months after arthrocentesis. Twelve patients had no treatment after the SF aspiration. Second SF samples were obtained from all patients at 3 months post arthrocentesis. IL-6, MDA, and 8-OHdG levels in the samples were evaluated. All patients showed a significant symptomatic improvement after treatment (P < 0.005). No statistical correlation was found between the two groups concerning pre-treatment and 3-month SF levels of MDA, 8-OHdG, and IL-6. Although splint therapy was found to be successful in eliminating clinical symptoms of TMD, the results showed no beneficial effect on inflammation and oxidative stress markers in the synovial fluid.     

Large effect of membrane tension on the fluid–solid phase transitions of two-component phosphatidylcholine vesicles

Model phospholipid membranes and vesicles have long provided insight into the nature of confined materials and membranes while also providing a platform for drug delivery. The rich thermodynamic behavior and interesting domain shapes in these membranes have previously been mapped in extensive studies that vary temperature and composition; however, the thermodynamic impact of tension on bilayers has been restricted to recent reports of subtly reduced fluid–fluid transition temperatures. In two-component phosphatidylcholine unilamellar vesicles [1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)], we report a dramatic influence of tension on the fluid–solid transition and resulting phases: At fixed composition, systematic variations in tension produce differently shaped solid domains (striped or irregular hexagons), shift fluid–solid transition temperatures, and produce a triple-point–like intersection of coexistence curves at elevated tensions, about 3 mN/m for 30% DOPC/70% DPPC. Tension therefore represents a potential switch of microstructure in responsive engineered materials; it is an important morphology-determining variable in confined systems, and, in biological membranes, it may provide a means to regulate dynamic structure.Phospholipid vesicles, capsular lamellar assemblies of phospholipid amphiphiles, are model systems that have advanced our perceptions of material surfaces and thin films, facilitated drug delivery technologies, and anchored the understanding of biological membranes to fundamental physics. Extensive studies of phase transitions in phospholipid bilayers and vesicles have focused almost exclusively on temperature and composition, revealing complex phase behavior (1–6) and beautiful patterns in the domain shapes within vesicle membranes (4, 6, 7). Tension has been mostly neglected as a thermodynamic variable and is unspecified in phase diagrams of vesicle membranes, although in analogous studies of phospholipid monolayers, surface pressure is known to drive transitions between gas-like layers, liquid fluids, and ordered crystals, which are sometimes polymorphic (8–10). Besides its fundamental thermodynamic importance, membrane tension may be biologically important, because stresses on cells can dominate their interactions (11–14) and fates (15). Indeed, tension has been proposed to regulate the dynamic structure of the cellular surface, for instance through coupling with curvature (16) or by clustering proteins in “rafts” (17, 18).Used as a mechanical variable, tension can stretch or bend uniform bilayers (19, 20). In multicomponent vesicles containing coexisting fluid domains, coupling of line tension with membrane bending determines vesicle shapes and drives budding transitions (21–24). Tension has also been hypothesized, but not confirmed, to influence the shapes of solid domains (25). Relevant to the current focus on the thermodynamic role of tension, tension was shown reduce the liquid–liquid coexistence temperature only slightly (a fraction of a Celsius degree for each 0.1 mN/m in tension) in cholesterol-containing phospholipid vesicles (26, 27).In the current work, we systematically examine the broader thermodynamic impact of membrane tension on the phase behavior of two-component phosphatidylcholine (PC) lipid vesicles: PC amphiphiles are an important class of molecules because of their prominence in cell membranes. Important to note, their relatively large hydrated head groups enable PC lipids, in single-component membranes, to order into solid bilayers of differing molecular areas [by about 10% (19)], such as ripple (P_β′) and tilt (“gel” or L_β′) phases (19, 28–31).To quantitatively probe the impact of membrane tension on the fluid–solid transition(s) of two-component PC bilayers, giant unilamellar vesicles containing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were chosen as model membranes. This work focuses on the impact of tension and temperature at the single-membrane composition of 30 mol% DOPC/70 mol% DPPC, taking a constant-composition slice through thermodynamic space, which qualitatively reflects behaviors at other compositions. Well-hydrated DOPC lamellae melt at Tm = −17 ± 1 °C (32), whereas hydrated DPPC bilayers have a higher main transition Tm = 41.5 ± 0.5 °C and a so-called “pretransition” at Tp = 35.5 ± 0.5 °C (28, 33). The ripple solid is found below the main transition temperature, whereas a tilt gel phase is observed below the pretransition temperature; however, many studies of DPPC-containing mixtures cannot distinguish these two solids (6, 34). Cooling mixed vesicles from the miscible fluid regime at elevated temperatures produces solid-like membrane domains comprised predominantly of DPPC (3, 34, 35). Indeed, cooling from the one phase region is the typical protocol for reliably creating solid domains and measuring transition temperatures.We report here that in two-component phosphatidylcholine membranes, even though the main fluid–solid transition temperature is only mildly reduced with increased tension, consistent with first principles, tension alters the equilibrium and the nature of the solid domains within the fluid membrane. The latter include the molecular ordering and shapes of the domains. Additionally, by shifting a second coexistence line in the opposite direction from the main transition curve, tension produces a triple-point–like feature at their intersection. Tension can thus be manipulated to select which solid phase forms on cooling, in turn directing domain morphology.     

钙和氧自由基在急性心肌梗死时线粒体膜介导的细胞死亡途径中的作用

在急性心肌梗死时,过量产生的活性氧和细胞内钙积聚对启动程序性细胞死亡起重要作用。细胞死亡包括坏死、凋亡、自噬及其共同作用。在缺血过程中,肌浆网、肌丝之间的钙处理被中断,同时钙转移至线粒体导致其肿胀,再灌注激活能量传导和心肌收缩导致氧自由基释放及其他离子失衡,在急性缺血一再灌注过程中,主要的死亡途径是线粒体通透性转换孔开放和线粒体外膜通透性增加启动内源性程序性坏死和凋亡。尽管国内外学者做了深入的研究,但调节线粒体膜通透性的作用和机制尚未完全了解。外源性凋亡、坏死性凋亡和自噬也可能加重缺血一再灌注所致的损伤。在这篇综述中,我们将讨论心肌梗死时钙失调和氧自由基、Bcl一2蛋白、线粒体膜通透性改变在心肌细胞死亡途径中的作用。     

关节液中脂联素水平与膝关节骨关节炎严重程度的相关性研究

背景：众所周知,肥胖是引起骨关节炎发生、发展的危险因素之一。肥胖人群容易发生关节炎的原因是超载作用和代谢因素。脂肪组织是一个活跃的器官,它的分泌脂肪细胞因子包括脂联素进入全身循环,参与了骨关节炎的发病。 目的：测量骨关节炎患者血清和关节滑液中脂联素水平,分析其与膝关节骨关节炎严重程度的相关性。 方法：64例膝关节骨关节炎患者（关节炎组）和19例因半月板或韧带损伤患者（对照组,行关节镜检查后排除软骨损伤）被纳入本研究。采用Kellgren-Lawrence（KL）标准对关节炎患者的膝关节前后位X线片进行评估分级。使用酶联免疫吸附试验检测脂联素在对照组和关节炎组患者血清和关节滑液中的表达水平。使用WOMAC量表（Western On-tario and McMaster Universities Arthritis Index）评估患者膝关节功能。 结果：骨关节炎组患者血清中的脂联素水平[（6177.8±991.0）ng/ml]高于对照组[（5793.4±673.3）ng/ml],但差异无统计学意义（P=0.12）。但在骨关节炎组患者,血清中的脂联素浓度[（6177.8±991.0）ng/ml]显著高于关节滑液中的脂联素[（824.3±304.7）ng/ml,P〈0.001）。关节炎患者关节液中脂联素浓度与评估疾病的严重程度呈负相关（r=-0.51,P〈0.001）,但血清脂联素浓度与疾病的严重程度关联不显著（r=-0.17,P=0.18）。血清脂联素水平、滑膜液脂联素水平与MOMAC疼痛评分均不显著相关（r=-0.01和r=-0.13,P＞0.05）。 结论：骨关节炎患者滑膜液中脂联素水平与膝关节炎严重程度呈负相关。检测关节滑液中的脂联素可能有助于早期发现关节炎。     

A broadly-protective vaccine against meningococcal disease in sub-Saharan Africa based on Generalized Modules for Membrane Antigens (GMMA)

Introduction

Neisseria meningitidis causes epidemics of meningitis in sub-Saharan Africa. These have mainly been caused by capsular group A strains, but W and X strains are increasingly contributing to the burden of disease. Therefore, an affordable vaccine that provides broad protection against meningococcal disease in sub-Saharan Africa is required.

Methods

We prepared Generalized Modules for Membrane Antigens (GMMA) from a recombinant serogroup W strain expressing PorA P1.5,2, which is predominant among African W isolates. The strain was engineered with deleted capsule locus genes, lpxL1 and gna33 genes and over-expressed fHbp variant 1, which is expressed by the majority of serogroup A and X isolates.

Results

We screened nine W strains with deleted capsule locus and gna33 for high-level GMMA release. A mutant with five-fold increased GMMA release compared with the wild type was further engineered with a lpxL1 deletion and over-expression of fHbp. GMMA from the production strain had 50-fold lower ability to stimulate IL-6 release from human PBMC and caused 1000-fold lower TLR-4 activation in Human Embryonic Kidney cells than non-detoxified GMMA. In mice, the GMMA vaccine induced bactericidal antibody responses against African W strains expressing homologous PorA and fHbp v.1 or v.2 (geometric mean titres [GMT] = 80,000–200,000), and invasive African A and X strains expressing a heterologous PorA and fHbp variant 1 (GMT = 20–2500 and 18–5500, respectively). Sera from mice immunised with GMMA without over-expressed fHbp v.1 were unable to kill the A and X strains, indicating that bactericidal antibodies against these strains are directed against fHbp.

Conclusion

A GMMA vaccine produced from a recombinant African N. meningitidis W strain with deleted capsule locus, lpxL1, gna33 and overexpressed fHbp v.1 has potential as an affordable vaccine with broad coverage against strains from all main serogroups currently causing meningococcal meningitis in sub-Saharan Africa.