Synaptosomal Actin Dynamics in the Developmental Visual Cortex Regulate Behavioral Visual Acuity in Rats.

Purpose: Synaptosomal actin dynamics are essential for synaptic structural stability. Whether actin dynamics are involved in structural and functional synaptic plasticity within the primary visual cortex (V1) or behavioral visual acuity in rats has still not been thoroughly investigated. Methods: Synaptosome preparation and western blot analysis were used to analyze synaptosomal actin dynamics. Transmission electron microscopy was used to detect synaptic density and mitochondrial area alterations. A visual water maze task was applied to assess behavioral visual acuity. Microinjection of the actin polymerization inhibitor or stabilizer detected the effect of actin dynamics on visual function. Results: Actin dynamics, the mitochondrial area, and synaptic density within the area of V1 are increased during the critical period for the development of binocularity. Microinjection of the actin polymerization inhibitor cytochalasin D into the V1 decreased the mitochondrial area, synaptic density, and behavioral visual acuity. Long-term monocular deprivation reduced actin dynamics, the mitochondrial area, and synaptic density within the V1 contralateral to the deprived eye compared with those ipsilateral to the deprived eye and impaired visual acuity in the amblyopic eye. In addition, the mitochondrial area, synaptic density, and behavioral visual acuity were improved by stabilization of actin polymerization by jasplakinolide microinjection. Conclusions: During the critical period of visual development of binocularity, synaptosomal actin dynamics regulate synaptic structure and function and play roles in behavioral visual acuity in rats.

Tprn is essential for the integrity of stereociliary rootlet in cochlear hair cells in mice.

Tprn encodes the taperin protein, which is concentrated in the tapered region of hair cell stereocilia in the inner ear. In humans, TPRN mutations cause autosomal recessive nonsyndromic deafness (DFNB79) by an unknown mechanism. To determine the role of Tprn in hearing, we generated Tprn-null mice by clustered regularly interspaced short palindromic repeat/Cas9 genome-editing technology from a CBA/CaJ background. We observed significant hearing loss and progressive degeneration of stereocilia in the outer hair cells of Tprn-null mice starting from postnatal day 30. Transmission electron microscopy images of stereociliary bundles in the mutant mice showed some stereociliary rootlets with curved shafts. The central cores of the stereociliary rootlets possessed hollow structures with surrounding loose peripheral dense rings. Radixin, a protein expressed at stereocilia tapering, was abnormally dispersed along the stereocilia shafts in Tprn-null mice. The expression levels of radixin and ß-actin significantly decreased.We propose that Tprn is critical to the retention of the integrity of the stereociliary rootlet. Loss of Tprn in Tprn-null mice caused the disruption of the stereociliary rootlet, which resulted in damage to stereociliary bundles and hearing impairments. The generated Tprn-null mice are ideal models of human hereditary deafness DFNB79.

Meclofenamic Acid Reduces Reactive Oxygen Species Accumulation and Apoptosis, Inhibits Excessive Autophagy, and Protects Hair Cell-Like HEI-OC1 Cells From Cisplatin-Induced Damage.

Hearing loss is the most common sensory disorder in humans, and a significant number of cases is due to the ototoxicity of drugs such as cisplatin that cause hair cell (HC) damage. Thus, there is great interest in finding agents and mechanisms that protect HCs from ototoxic drug damage. It has been proposed that epigenetic modifications are related to inner ear development and play a significant role in HC protection and HC regeneration; however, whether the m6A modification and the ethyl ester form of meclofenamic acid (MA2), which is a highly selective inhibitor of FTO (fatmass and obesity-associated enzyme, one of the primary human demethylases), can affect the process of HC apoptosis induced by ototoxic drugs remains largely unexplored. In this study, we took advantage of the HEI-OC1 cell line, which is a cochlear HC-like cell line, to investigate the role of epigenetic modifications in cisplatin-induced cell death. We found that cisplatin injury caused reactive oxygen species accumulation and increased apoptosis in HEI-OC1 cells, and the cisplatin injury was reduced by co-treatment with MA2 compared to the cisplatin-only group. Further investigation showed that MA2 attenuated cisplatin-induced oxidative stress and apoptosis in HEI-OC1 cells. We next found that the cisplatin-induced upregulation of autophagy was significantly inhibited after MA2 treatment, indicating that MA2 inhibited the cisplatin-induced excessive autophagy. Our findings show that MA2 has a protective effect and improves the viability of HEI-OC1 cells after cisplatin treatment, and they provide new insights into potential therapeutic targets for the amelioration of cisplatin-induced ototoxicity.

Myosin II regulates actin rearrangement-related structural synaptic plasticity during conditioned taste aversion memory extinction.

Similar to memory formation, memory extinction is also a new learning process that requires synaptic plasticity. Actin rearrangement is fundamental for synaptic plasticity, however, whether actin rearrangement in the infralimbic cortex (IL) plays a role in memory extinction, as well as the mechanisms underlying it, remains unclear. Here, using a conditioned taste aversion (CTA) paradigm, we demonstrated increased synaptic density and actin rearrangement in the IL during the extinction of CTA. Targeted infusion of an actin rearrangement inhibitor, cytochalasin D, into the IL impaired memory extinction and de novo synapse formation. Notably, we also found increased myosin II phosphorylation in the IL during the extinction of CTA. Microinfusion of a specific inhibitor of the myosin II ATPase, blebbistatin (Blebb), into the IL impaired memory extinction as well as the related actin rearrangement and changes in synaptic density. Moreover, the extinction deficit and the reduction of synaptic density induced by Blebb could be rescued by the actin polymerization stabilizer jasplakinolide (Jasp), suggesting that myosin II acts via actin filament polymerization to stabilize synaptic plasticity during the extinction of CTA. Taken together, we conclude that myosin II may regulate the plasticity of actin-related synaptic structure during memory extinction. Our studies provide a molecular mechanism for understanding the plasticity of actin rearrangement-associated synaptic structure during memory extinction.

Otitis media in sperm-associated antigen 6 (Spag6)-deficient mice.

Mammalian SPAG6 protein is localized to the axoneme central apparatus, and it is required for normal flagella and cilia motility. Recent studies demonstrated that the protein also regulates ciliogenesis and cilia polarity in the epithelial cells of brain ventricles and trachea. Motile cilia are also present in the epithelial cells of the middle ear and Eustachian tubes, where the ciliary system participates in the movement of serous fluid and mucus in the middle ear. Cilia defects are associated with otitis media (OM), presumably due to an inability to efficiently transport fluid, mucus and particles including microorganisms. We investigated the potential role of SPAG6 in the middle ear and Eustachian tubes by studying mice with a targeted mutation in the Spag6 gene. SPAG6 is expressed in the ciliated cells of middle ear epithelial cells. The orientation of the ciliary basal feet was random in the middle ear epithelial cells of Spag6-deficient mice, and there was an associated disrupted localization of the planar cell polarity (PCP) protein, FZD6. These features are associated with disordered cilia orientation, confirmed by scanning electron microscopy, which leads to uncoordinated cilia beating. The Spag6 mutant mice were also prone to develop OM. However, there were no significant differences in bacterial populations, epithelial goblet cell density, mucin expression and Eustachian tube angle between the mutant and wild-type mice, suggesting that OM was due to accumulation of fluid and mucus secondary to the ciliary dysfunction. Our studies demonstrate a role for Spag6 in the pathogenesis of OM in mice, possibly through its role in the regulation of cilia/basal body polarity through the PCP-dependent mechanisms in the middle ear and Eustachian tubes.

Effect of Yiguanjian decoction on cell differentiation and proliferation in CCl4-treated mice.

AIM: To investigate the cellular mechanisms of action of Yiguanjian (YGJ) decoction in treatment of chronic hepatic injury. METHODS: One group of mice was irradiated, and received enhanced green fluorescent protein (EGFP)-positive bone marrow transplants followed by 13 wk of CCl4 injection and 6 wk of oral YGJ administration. A second group of Institute for Cancer Research mice was treated with 13 wk of CCl4 injection and 6 wk of oral YGJ administration. Liver function, histological changes in the liver, and Hyp content were analyzed. The expression of α-smooth muscle actin (α-SMA), F4/80, albumin (Alb), EGFP, mitogen-activated protein kinase-2 (PKM2), Ki-67, α fetoprotein (AFP), monocyte chemotaxis protein-1 and CC chemokine receptor 2 were assayed. RESULTS: As hepatic damage progressed, EGFP-positive marrow cells migrated into the liver and were mainly distributed along the fibrous septa. They showed a conspicuous coexpression of EGFP with α-SMA and F4/80 but no coexpression with Alb. Moreover, the expression of PKM2, AFP and Ki-67 was enhanced dynamically and steadily over the course of liver injury. YGJ abrogated the increases in the number of bone marrow-derived fibrogenic cells in the liver, inhibited expression of both progenitor and mature hepatocyte markers, and reduced fibrogenesis. CONCLUSION: YGJ decoction improves liver fibrosis by inhibiting the migration of bone marrow cells into the liver as well as inhibiting their differentiation and suppressing the proliferation of both progenitors and hepatocytes in the injured liver.

[The analysis of the influencing factors of mortality rate in the transplantation of mouse bone marrow].

The purpose of the study was to investigate the influencing factors of mortality rate in the bone marrow transplantation in mice. The recipient mice receiving whole-body irradiation of gamma-ray were infused with the same strain of bone marrow cells or the mixture of the bone marrow cells and splenocytes respectively. Experiments were carried out in four batches, with different strains of mice used, respectively. The manifestations and the appearance of graft-versus-host disease (GVHD) were observed, as well as the mortality rate within 35 d of the transplantation in the recipient mice. The mortality rate of the first group of recipient mice was the lowest, the mortality rate of the second group of recipient mice was the highest and the obvious GVHD performance was observed before death. In the third group, the mortality rate declined and there was statistical significance compared to that of the second group. The mortality rate of the fourth group of mice was higher than that of the third group, but still lower than that of the second group of mice and there is a statistical significance. This evidence suggested that mouse genetic purity, splenocytes, the ratio of the bone marrow cells and splenocytes and the week-old of the mouse could be the important influencing factors of the mortality rate in mouse bone marrow transplantation.

A comparison of proliferative capacity and passaging potential between neural stem and progenitor cells in adherent and neurosphere cultures.

Neural stem and progenitor cells (NSPCs) can be isolated from the fetal or adult brain and expanded in culture for potential use in basic research, drug discovery and cell therapy. In the present study, two culture systems have been commonly used to maintain and expand NSPCs isolated from mammalian CNS: neurosphere and adhesive substrate-bound monolayer culture. NSPCs were isolated from the neuroepithelium of E14 embryonic rat cerebral cortex and maintained and expanded on fibronectin substrates or within neurospheres in serum-free medium. Ultrastructural study under transmission electron microscope revealed similar characteristics of immature morphology of NSPCs in adherent and neurosphere cultures. NSPCs cultured on adherent substrates and within neurospheres shared the properties of self-renewal and multipotency, but little is known about proliferation capacity and passaging potential of adherent NSPCs compared to neurosphere culture. We found that the self-renewal capacity of NSPCs in adherent culture was higher than that in neurosphere culture in the P1 and P3 passages, and reduced after the P5 passage. At the same time, comparative analysis using BrdU incorporation and immunostaining for nestin indicated that NSPCs grew significantly faster in primary cultures on adherent substrates than within neurospheres. Whereas, NSPCs in adherent culture could not maintain such robust growth for more than 6 passages. The growth of NSPCs within neurospheres was slower than that in adherent culture, but increased steadily and could be maintained for more than 10 passages. These data provide useful information for large scale in vitro expansion of NSPCs required by potential drug screening and cell therapy.

Region-specific involvement of actin rearrangement-related synaptic structure alterations in conditioned taste aversion memory.

Actin rearrangement plays an essential role in learning and memory; however, the spatial and temporal regulation of actin dynamics in different phases of associative memory has not been fully understood. Here, using the conditioned taste aversion (CTA) paradigm, we investigated the region-specific involvement of actin rearrangement-related synaptic structure alterations in different memory processes. We found that CTA training could induce increased postsynaptic density (PSD) length in insular cortex (IC), but not in basolateral amygdala (BLA) and prelimbic cortex (PrL) during short-term memory (STM) formation, whereas it led to increased PSD length and synapse density in both IC and PrL during long-term memory (LTM) formation. Inhibition of actin rearrangement in the IC, but not in the BLA and PrL, impaired memory acquisition. Furthermore, actin dynamics in the IC or PrL is necessary for memory consolidation. On the contrary, inhibition of actin dynamics in the IC, BLA, or PrL had no effect on CTA memory retrieval. Our results suggest temporal and regional-specific regulation of actin rearrangement-related synaptic structure in different phases of CTA memory.

NADPH oxidase-derived ROS contributes to upregulation of TRPC6 expression in puromycin aminonucleoside-induced podocyte injury.

Recent studies have demonstrated upregulation of transient receptor potential cation channel 6 (TRPC6) contributes to podocyte injury in acquired forms of proteinuric kidney diseases, such as focal segmental glomerulosclerosis (FSGS). However, under these pathophysiological conditions, the mechanisms of regulation of TRPC6 expression and activity remain unknown. The present study tested the hypothesis that NADPH oxidase-mediated redox signaling importantly participates in the development of podocyte injury by regulation of TRPC6 expression and activity. Injection of puromycin aminonucleoside (PAN) to rats produced severe proteinuria and mimics the lesions of FSGS. Podocyte effacement, NADPH oxidase subunit NOX4 expression, enzyme activity and TRPC6 expression were significant increased in glomeruli from PAN nephrosis rats. Inhibition of NADPH oxidase activity by apocynin ameliorated proteinuria and podocyte effacement and reduced TRPC6 expression. In in vitro study, PAN significantly increased NOX4 and TRPC6 expression levels in cultured podocytes. This increased TRPC6 expression was attenuated by apocynin or siRNA-NOX4. Our results provide direct evidence for the first time that NADPH oxidase-derived reactive oxygen species (ROS) is one of critical components of a signal transduction pathway that links PAN nephrosis to TRPC6-mediated Ca(2+) signaling.

Marchantin C, a novel microtubule inhibitor from liverwort with anti-tumor activity both in vivo and in vitro.

Microtubules are long-standing targets in cancer chemotherapy. Previously, we reported that marchantin C triggers apoptosis of human tumor cells. We show here that marchantin C induced cell cycle arrest at G(2)/M phase in A172 and HeLa cells. In addition, marchantin C decreased the quantity of microtubules in a time- and dose-dependent manner in these cells. Exposure of purified bovine brain tubulin to marchantin C inhibited polymerization of gross tubulin in vitro. Moreover, marchantin C potently suppressed the growth of human cervical carcinoma xenografts in nude mice. Marchantin C-treated xenografts showed decreased microtubules, Bcl-2 and increased cyclin B1, Bax, caspase-3, indicating that marchantin C possess the same ability to induce microtubules depolymerization and tumor cell apoptosis in tumor-bearing mice as in vitro. In conclusion, marchantin C is a novel microtubule inhibitor that induces mitotic arrest of tumor cells and suppresses tumor cell growth, exhibiting promising antitumor therapeutic potential.

Electron-microscopic observation of mouse spleen tissue infected with Orientia tsutsugamushi isolated from Shandong, China.

Low-virulent Orientia tsutsugamushi (Ot) were successfully isolated from scrub typhus patients in Shandong, China, and the isolates were similar to the Kawasaki type identified by nested polymerase chain reaction (PCR). To identify the morphological characterization of the low-virulent Ot, and elucidate the pathological changes on host cells, mouse spleen tissue infected with the Ot isolated from Shandong was used for the ultrastructural study. Transmission electron microscopy showed that the Ot parasitized in the spleen were different in size, shape and electron density and many significant changes occurred in cytoplasmic organelles of the inoculated mouse spleen cells. Swollen perinuclear cisterna was observed in the nuclear membranes of mononuclear cells and a multivesicular body was found in the intracytoplasm of the macrophage. In the phagosome of the macrophage, many Ot enveloped with an additional membrane were found to push the phagosomal membrane outward from inside. The results indicated that the low-virulent Ot and the spleen cells suffered various damages.

Spontaneous vesicle formation and vesicle-tubular microstructure transition in aqueous solution of a poly-tailed cationic and anionic surfactants mixture.

Spontaneous vesicle formation has been observed in aqueous mixtures of tri-(N-dodecyldimethylhydroxypropylammonium chloride) phosphate (PTA) and bis-(2-ethylhexyl) sulfosuccinate (Aerosol OT), which is supported by negative-staining TEM and dynamic light scattering. The range of vesicle formation in the PTA/AOT mixtures is wide and monodisperse vesicles are obtained. The vesicle diameter increases with the total surfactant concentration. Tubular microstructures, vesicle fusion, and vesicle-tubular microstructure transition have been also observed by negative-staining TEM. The vesicle formation mechanism is discussed from the viewpoint of molecular geometry, conformation, and the interaction between surfactant molecules.