Administration of Aggregated Beta-Amyloid Peptide (25–35) Induces Changes in Long-Term Potentiation in the Hippocampus in Vivo

Intracerebroventricular administration of aggregated -amyloid protein fragment (25–35) (7.5 nmol/ventricle) was followed one month later by significant changes in the dynamics of long-term potentiation in the hippocampus in vivo, expressed as powerful and stable increases in the amplitude of evoked potentials. This phenomenon may be associated with oxidative stress in the hippocampus, which has previously been demonstrated in this model, and, thus, with disturbances in ion homeostasis.     

Studies of the Effects of Central Administration of β-Amyloid Peptide (25–35): Pathomorphological Changes in the Hippocampus and Impairment of Spatial Memory

The possible link between amnesia induced by central administration of β-amyloid (25–35) (Aβ(25–35)) and neurodegenerative changes in the hippocampus was studied. Male Wistar rats received single intracerebroventricular injections of Aβ(25–35) at a dose of 15 nmoles and one month later were trained in an eight-arm radial maze. Training was followed by histological assessment of the state of the hippocampus on brain sections stained with hematoxylin and eosin. Aβ(25–35) induced impairments in long-term (reference) and working memory on testing in the maze. There was a moderate reduction in the number of neurons in hippocampal field CA1; there was no change in the number of cells in field CA3. The numbers of errors made by the animals on testing in the maze were found to correlate negatively with the numbers of nerve cells in hippocampal field CA1. Thus, this is the first demonstration that impairments of learning and memory induced by single doses of Aβ(25–35) are specifically associated with neurodegenerative changes in hippocampal field CA1 in rats. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 54, No. 5, pp. 705–711, September–October, 2004.     

Changes in Cell Proliferation in the Subventricular Zone of the Brain in Adult Rats Given β-Amyloid Peptide (25–35)

The effects of intracerebroventricular administration of fragment (25–35) of β-amyloid peptide [Aβ(25–35)] on cell proliferation in the subventricular zone of the dentate gyrus of the hippocampus in adult rats were analyzed. Animals received doses of 15 nmol of pre-aggregated Aβ(25–35) or the Aβ(35–25) control peptide, or solvent (sterile water) into the lateral ventricles. On post-injection days 1–5, rats received intraperitoneal injections of the thymidine analog 5-bromo-2’-deoxyuridine (BrdU). BrdU incorporated into DNA was detected immunohistochemically on frontal brain sections six and 12 days after peptide administration. At six days, the numbers of BrdU-containing cells in the subventricular zone showed no differences between the study groups. At 12 days, the total number of BrdU-positive cells decreased significantly in all study groups. At the same time, the number of labeled cells in rats given Aβ(25–35) was significantly greater in this brain zone than in animals given water or the control peptide. Thus, Aβ(25–35) significantly increased cell proliferation in the subventricular zone after intracerebroventricular administration.     

Effects of β-amyloid (25–35) on learning in the common snail

The effects of neurotoxic β-amyloid fragment (25–35) on the formation of behavioral sensitization and a conditioned defensive reflex to food were studied. Administration of β-amyloid (25–35) to common snails before the start of training led to a significant reduction in sensitization of the defensive reaction, weakening of the formation of the conditioned defensive reflex to food, and impairment of memory. These impairments to behavioral plasticity may be mediated by changes in synaptic plasticity previously observed in the presence of β-amyloid. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 57, No. 2, pp. 229–236, March–April, 2007.     

Impact of Amyloid-β Peptide (1–42) on Voltage-Gated Ion Currents in Molluscan Neurons

Different types of voltage-gated ion currents were recorded in isolated neurons of snail Helix pomatia using the two-microelectrode voltage-clamp technique. Application of amyloid-β peptide (1–42, 1–10 μM) in the bathing solution did not change delayed rectifier K⁺-current and leakage current, but enhanced inactivation of Ca²⁺-current and blocked Ca²⁺-dependent К⁺-current.     

Effects of dexamethasone on the expression of β1-, β2- and β3-adrenoceptor mRNAs in skeletal and left ventricle muscles in rats

Glucocorticoids are known to increase the density and mRNA levels of β-adrenoceptors (β-AR) via the glucocorticoid receptor (GR) in many tissues. However, the effects of these changes in the skeletal and cardiac muscles remain relatively unknown. We have investigated the effects of dexamethasone on the expression of the β₁-, β₂-, and β₃-AR mRNAs and GR mRNA in fast-twitch fiber-rich extensor digitorum longus (EDL), slow-twitch fiber-rich soleus (SOL), and left ventricle (LV) muscles by real-time quantitative RT-PCR. Male rats were divided into a dexamethasone group and control group. The weight, RNA concentration, and total RNA content of EDL muscle were 0.76-, 0.85-, and 0.65-fold lower, respectively, in the dexamethasone group than in the control group. The weight, RNA concentration, and total RNA content of SOL muscle were 0.92-, 0.87-, and 0.81-fold lower, respectively, in the dexamethasone group than in the control group; these differences were significant. However, the weight/body weight and total RNA content/body weight of LV muscle were 1.38- and 1.39-fold higher, respectively, in the dexamethasone group than in the control group, respectively; these differences were also significant. Dexamethasone significantly decreased GR mRNA expression in EDL muscle without changing the expression of the β₁-, β₂-, and β₃-AR mRNAs. However, dexamethasone significantly decreased the expressions of β₂-AR and GR mRNAs in SOL muscle and significantly increased β₁-AR mRNA expression in LV muscle—without changing GR mRNA expression. These results suggest that the effects of dexamethasone on the expression of β₁- and β₂-AR mRNAs and muscle mass depend on the muscle contractile and/or constructive types.     

Relationship between Long-Term Potentiation and the Initial Properties of CA3–CA1 Synapses: Importance of the Effects of External Factors on Hippocampal Synaptic Plasticity for Studies

Neuroscience and Behavioral Physiology - The phenomenon of long-term potentiation (LTP) is used for studies of the effects of various factors on the long-term plasticity of synapses in health and...     

Effects of β-guanidinopropionic acid-feeding on the patterns of myosin isoforms in rat fast-twitch muscle

Administration of -guanidinopropionic acid (-GPA) to rats as 1% of their diet for 6 weeks led to an accumulation of -GPA and -GPA-phosphate and to a depletion of creatine and phosphocreatine in the fast-twitch plantaris muscle. Adenosine triphosphate concentration was also decreased. Electrophoretic analyses were performed to investigate the effects of -GPA on the patterns of fast (FM) and slow (SM) isomyosins, myosin heavy chain (HC) isoforms and myosin light chain (LC) isoforms. The relative concentrations of fast isomyosins FM1 and FM2 decreased, whereas slow isomyosin SM increased. The increase in slow isomyosin corresponded to an increase in the relative concentration of the slow myosin HCI. The changes of the myosin light chain pattern consisted of increases in the relative concentrations of the two slow isoforms, LC1sb and LC2s, and decreases in the fast isoforms LC2f and LC3f. These results demonstrate that -GPA administration, leading to a depletion in energy-rich phosphates and a reduced phosphorylation potential, has an impact on myosin isoform expression in rat fast-twitch skeletal muscle.     

Effects of Hericium erinaceus on amyloid β(25-35) peptide-induced learning and memory deficits in mice

The mushroom Hericium erinaceus has been used as a food and herbal medicine since ancient times in East Asia. It has been reported that H. erinaceus promotes nerve growth factor secretion in vitro and in vivo. Nerve growth factor is involved in maintaining and organizing cholinergic neurons in the central nervous system. These findings suggest that H. erinaceus may be appropriate for the prevention or treatment of dementia. In the present study, we examined the effects of H. erinaceus on amyloid β(25-35) peptide-induced learning and memory deficits in mice. Mice were administered 10 μg of amyloid β(25-35) peptide intracerebroventricularly on days 7 and 14, and fed a diet containing H. erinaceus over a 23-d experimental period. Memory and learning function was examined using behavioral pharmacological methods including the Y-maze test and the novel-object recognition test. The results revealed that H. erinaceus prevented impairments of spatial short-term and visual recognition memory induced by amyloid β(25-35) peptide. This finding indicates that H. erinaceus may be useful in the prevention of cognitive dysfunction.     

Effects of Stress on Mouse β-Defensin-3 Expression in the Upper Digestive Mucosa

Purpose

Gastrointestinal integrity and immune surveillance are affected by stress. Stress also adversely affects mucosal barrier function. β-defensins constitute an integral component of the innate immune system as antimicrobial peptides, serving as the first line of defense against microbial pathogens at the epithelial surfaces of the upper digestive mucosa. The primary objective of this study was to determine the effects of stress on the expression profile of mouse β-defensin-3 in the upper digestive mucosa of mice with diabetes.

Materials and Methods

We established a mouse model of restraint stress by using NSY/Hos mice with type 2 diabetes mellitus. We used real-time polymerase chain reaction, in situ hybridization, and immunohistochemistry to investigate the effects of stress and glucocorticoid administration on mouse β-defensin-3 expression in the upper digestive mucosa of the gingiva, esophagus, and stomach.

Results

Mouse β-defensin-3 mRNA expression was higher in the esophagus than in the gingiva or stomach (p<0.05). In the esophagus, mouse β-defensin-3 mRNA expression was lower in stressed mice than in non-stressed mice (p<0.05). Furthermore, immunoreactivity to mouse β-defensin-3 protein was lower in the esophagus of stressed mice than non-stressed mice, consistent with the results of mRNA expression analysis. Systemic glucocorticoid administration also downregulated esophageal mouse β-defensin-3 mRNA expression.

Conclusion

Our novel findings show that stress decreases mouse β-defensin-3 expression in the esophagus of mice with diabetes, possibly due to increased endogenous glucocorticoid production. It appears to be highly likely that stress management may normalize mucosal antimicrobial defenses in patients with diabetes.     

Role of the Macrophage Inflammatory Protein-1α/CC Chemokine Receptor 5 Signaling Pathway in the Neuroinflammatory Response and Cognitive Deficits Induced by β-Amyloid Peptide

The hallmarks of Alzheimer’s disease include the deposition of β-amyloid (Aβ), neuroinflammation, and cognitive deficits. The accumulation of activated glial cells in cognitive-related areas is critical for these alterations, although little is known about the mechanisms driving this event. Herein we used macrophage inflammatory protein-1α (MIP-1α^−/−)- or CC-chemokine receptor 5 (CCR5^−/−)-deficient mice to address the role played by chemokines in molecular and behavioral alterations induced by Aβ_1–40. Aβ_1–40 induced a time-dependent increase of MIP-1α mRNA followed by accumulation of activated glial cells in the hippocampus of wild-type mice. MIP-1α^−/− and CCR5^−/− mice displayed reduced astrocytosis and microgliosis in the hippocampus after Aβ_1–40 administration that was associated with decreased expression of cyclooxygenase-2 and inducible nitric oxide synthase, as well as reduced activation of nuclear factor-κB, activator protein-1 and cyclic AMP response element-binding protein. Furthermore, MIP-1α^−/− and CCR5^−/− macrophages showed impaired chemotaxis in vitro, although cytokine production in response to Aβ_1–40 was unaffected. Notably, the cognitive deficits and synaptic dysfunction induced by Aβ_1–40 were also attenuated in MIP-1α^−/− and CCR5^−/− mice. Collectively, these results indicate that the MIP-1α/CCR5 signaling pathway is critical for the accumulation of activated glial cells in the hippocampus and, therefore, for the inflammation and cognitive failure induced by Aβ_1–40. Our data suggest MIP-1α and CCR5 as potential therapeutic targets for Alzheimer’s disease treatment.Alzheimer’s disease (AD) is the most prevalent cause of dementia in humans, and the symptoms are commonly manifested after the seventh decade of life. Numerous pathological changes have been described in the postmortem brains of AD patients, including senile plaques, tangles, neuroinflammation, synapse loss, and neuronal death.¹ Activated glial cells surrounding senile plaques seem to be responsible for the ongoing neuroinflammatory process in the disease through the release of cytokines and other toxic products, including reactive oxygen species, nitric oxide, and excitatory amino acids.² However, little is known about the identity of the agent(s) responsible for glial cell accumulation and activation in the AD brain.Chemokines belong to a family of chemoattractant cytokines that were initially identified according to their ability to regulate leukocyte trafficking during inflammatory responses.^3,4 More recently, in addition to their chemotactic activity, chemokines have been implicated in the modulation of cell adhesion, phagocytosis, cytokine secretion, proliferation, apoptosis, angiogenesis, and viral pathogenesis.⁵ In the central nervous system (CNS), these proteins regulate leukocyte migration across the brain endothelium as well as the activation and movement of cells within the brain parenchyma.⁶ There is growing evidence supporting the view that resident CNS cells have the capacity to express chemokines and their receptors during a variety of neuroinflammatory and degenerative conditions.^{7,8,9,10,11,12,13,14} Notably, recent evidence has indicated that chemokines and their receptors are up-regulated in the AD brain and that they may play a critical role in controlling the recruitment and accumulation of glial cells at β-amyloid (Aβ) sites in senile plaques.¹⁵Macrophage inflammatory protein (MIP)-1α (CCL3) is a member of the β-chemokine subfamily, which also includes MIP-1β (CCL4) and regulated on activation, normal T-cell expressed and secreted (RANTES, CCL5). These molecules exert their effects though activation of CC-chemokine receptor 5 (CCR5).⁴ CCR5 is expressed at low levels in the normal brain, but it can be induced to play important roles in various injuries or infections, including AD.⁵ In this context, immunohistochemical analyses have revealed the expression of CCR5, together with its ligands, on the microglia of both normal and AD brains, with increased expression on some reactive microglia in AD.¹¹ Nevertheless, the precise role of CCR5 and its ligand MIP-1α in AD is poorly understood so far.In the current study we have investigated the molecular and behavioral alterations induced by a single intracerebroventricular (i.c.v.) injection of Aβ_1–40 peptide in mice lacking MIP-1α or CCR5. Although unable to induce pathological AD hallmarks, the acute injection of Aβ peptides into the rodent brain is a useful experimental model for the characterization of Aβ toxicity, as it induces an inflammatory response associated with deficits of learning and memory.¹⁶ Using this model, we demonstrated that activation of the MIP-1α/CCR5 signaling pathway is one of the earliest events after Aβ_1–40 injection in mice, representing an important signal for the accumulation of activated glial cells and, consequently, for inflammatory response, synaptic dysfunction, and cognitive failure. These findings raise the possibility that MIP-1α and CCR5 represent promising targets for AD drug development.     

IFN-γ Inhibits the Suppressive Effects of PGE2 on the Production of Tumor Necrosis Factor-α by Mouse Macrophages

Tumor necrosis factor-α (TNF-α) has become known as a central mediator of responses to endotoxin, rheumatoid diseases, and other forms of inflammation. Current investigations indicate that the production of TNF-α is controlled by other mediators, including interferon-γ (IFN-γ) and prostaglandin E₂ (PGE₂). In the present study, we investigated the regulatory effects of IFN-γ and/or PGE₂ on LPS-induced TNF-α production and mRNA expression in mouse peritoneal macrophages using the enzyme immunoassay and Northern blot analysis, respectively. In response to 10 ng/ml of LPS, TNF-α production reached a maximum at approximately 4 hrs, followed by rapid decline. At the molecular level, TNF-α mRNA accumulated rapidly after LPS exposure, reaching a peak by 3 hr, and declined more rapidly than did the production of TNF-α. Exposure of macrophages to 100 U/ml of IFN-γ caused an increase in both the TNF-α production and mRNA expression induced by LPS. Exogenous PGE₂ caused a dose dependent reduction in LPS-induced TNF-α mRNA accumulation as well as TNF-α production. Macrophages primed with IFN-γ showed the reduced responsiveness to the suppressive effect of PGE₂ on the production of TNF-α and the accumulation of TNF-α mRNA. These findings indicate that the suppressive effects induced by PGE₂ on the accumulation of TNF-α mRNA as well as the production of TNF-α can be reduced by the pretreatment of macrophages with IFN-γ. These studies demonstrate the role of IFN-γ as an immunomodulating compound that may effectively regulate TNF-α production by modulation of macrophage responsiveness to PGE₂.     

The effect of transforming growth factor β1 (TGF-β1) on the regenerate bone in distraction osteogenesis

Distraction osteogenesis is a well established clinical treatment for limb length dicrepancy and skeletal deformities. Transforming growth factor beta 1 (TGF-β1) is a multifunctional peptide which controls proliferation and expression of cells specific to bone like chondrocytes, osteoblasts, osteoclasts including mesenchymal precursor cells.

To decrease the external fixation time with increasing the strength of regenerate (newly formed bone after distraction) we tested the effect of locally applied transforming growth factor beta 1 on distraction osteogenesis.

A total of 28 mature female white New zealand rabbits weighing 3,5 kg–4,5 kg were studied. 10 animals were belonging to biomechanical testing group (5 for the study and 5 for the control subgroups), and the others were to histology group. In biomechanical group after tibial ostetomy TGF-β1 was applied subperiosteally for 5 days just proximal to osteotomy site. Control group received only the solvent. Seven days after tibial osteotomy distraction was started at a rate of 0.25mm/12 hours for 3 weeks with a unilateral fixator. Rabbits were sacrified at the end of a consodilation period 8 week after tibial osteotomy. We assessed density of the elongation zone of rabbit tibial bones with the computed tomography.

Then biomechanical parametres were assessed using the torsional testing using the material testing machine. In histology group rabbits were classified as control and study (rabbits that were given TGF-β1). Rabbits were sacrified at the end of first week, second week and fourth week also at the end of consolidation period 8 week after tibial osteotomy. Immunohistochemical and histologic parameters were examined.

Biomechanical testing was applied as tortional testing. These values are used in determination of maximal loading, stiffness and energy absorbed during testing (brittlenes). The histomorphometric examination looked for the differences between the study and control groups in terms of bone formation pattern, bone quality and quantity. The immunohistochemical studies investigated the mechanism of TGF- β1, and it's presence in different cell types.

The results of this study suggest that locally applied TGF-β1 improves the mineral density of distraction gap and load to failure(energy absorbed during testing). Though there is no significant histomorphometric difference between the study and control groups, there is an increased bone mineral density and an according maximum energy absorbance in the study group. This effect can be explained by the following mechanism:

TGF-β1 exerts it's effect on two different receptor types (Type 1 and 2). Type 1 receptors are localized to bone matrix and type 2 receptors are localized to the intracellular space. The specific stains utilized in the current experiment are specific to type 2 receptors. They have been shown to be down-regulated by exogenous TGF-β1 injections. Most probably, type 1 receptors are up-regulated by this exogenous administration, but unfortunately, there is currently no specific stain on tha market to display type 1 receptors and to prove this explanation.     

Comparative study on the stability of soybean (Glycine max) β-conglycinin in vivo

The immunoreactivity and structural variation of β-conglycinin in digesta from digestive tracts of pigs were measured by inhibition ELISA and sodium dodecyl sulphate polyacrylamide gel electrophoresis, respectively. Results showed that the immunoreactivity disappearance proportion of β-conglycinin significantly increased from stomach to the caecum in all groups (P<0.05). In the stomach, upper-jejunum and middle-jejunum, the immunoreactivity disappearance proportion of β-conglycinin significantly increased among these three groups (P<0.05), while it has no significant difference in ileum and caecum (P>0.05). The α′, α subunits of β-conglycinin were easier to digest than the β subunit. It indicated that immunoreactivity disappearance proportion of β-conglycinin tended to increase with the growth of age and the descending down of digestive tract, while the β subunits of β-conglycinin are more stable to digestion than α′, α subunits.     

Time Course of Expression of “Early” Genes during Long-Term Posttetanic Potentiation in Rat Hippocampal CA1 Field

The expression of egr-1, junB, c-jun, and c-fos genes in rat hippocampal CA1 fi eld was studied by the real-time PCR 30, 60, and 120 min after induction of long-term posttetanic potentiation. The content of egr-1, junB, and c-jun mRNA gradually increased and doubled 120 min after tetanization. The increase in c-jun mRNA level lagged behind the increment of egr-1 and junB. The level of c-fos mRNA increased 30 min after tetanization, returned to the initial level by min 60, and again increased 120 min after induction of long-term posttetanic potentiation.