Effects of vitamin K3 and K5 on proliferation, cytokine production, and regulatory T cell-frequency in human peripheral-blood mononuclear cells.

AIMS: The effects of vitamin K (VK) derivatives VK3 and VK5 on human immune cells have not been extensively investigated. We examined the effects of VK3 and VK5 on proliferation, apoptosis, cytokine production, and CD4+CD25+Foxp3+ regulatory T (Treg) cell-frequency in human peripheral blood mononuclear cells (PBMCs) activated by T cell mitogen in vitro. MAIN METHODS: Anti-proliferative effects of VK3 and VK5 on T-cell mitogen activated PBMCs were assessed by WST assay procedures. Apoptotic cells were determined as Annexin V positive/propidium iodide (PI) negative cells. Cytokine concentrations in the supernatant of the culture medium were measured with bead-array procedures followed by analysis with flow cytometry. The CD4+CD25+Foxp3+Treg cells in mitogen-activated PBMCs were stained with fluorescence-labeled specific antibodies followed by flow cytometry. KEY FINDINGS: VK3 and VK5 suppressed the mitogen-activated proliferation of PBMCs significantly at 10-100µM (p<0.05). The data also suggest that VK3 and VK5 promote apoptosis in the mitogen-activated T cells. VK3 and VK5 significantly inhibited the production of tumor necrosis factor (TNF) α, interleukin (IL)-4, -6, and -10 from the activated PBMCs at 10-100µM (p<0.05). In contrast, VK3 and VK5 significantly increased Treg cell-frequency in the activated PBMCs at concentrations more than 10µM (p<0.001). SIGNIFICANCE: Our data suggest that VK3 and VK5 attenuate T cell mediated immunity by inhibiting the proliferative response and inducing apoptosis in activated T cells.

Kinetics of GABAB autoreceptor-mediated suppression of GABA release in rat insular cortex.

Release of GABA is controlled by presynaptic GABA receptor type B (GABA(B)) autoreceptors at GABAergic terminals. However, there is no direct evidence that GABA(B) autoreceptors are activated by GABA release from their own terminals, and precise profiles of GABA(B) autoreceptor-mediated suppression of GABA release remain unknown. To explore these issues, we performed multiple whole-cell, patch-clamp recordings from layer V rat insular cortex. Both unitary inhibitory and excitatory postsynaptic currents (uIPSCs and uEPSCs, respectively) were recorded by applying a five-train depolarizing pulse injection at 20 Hz. In connections from both fast-spiking (FS) and non-FS interneurons to pyramidal cells, the GABA(B) receptor antagonist CGP 52432 had little effect on the initial uIPSC amplitude. However, uIPSCs, responding to later pulses, were effectively facilitated. This CGP 52432-induced facilitation was prominent in the fourth uIPSCs, which were evoked 150 ms after the first uIPSC. The facilitation of uIPSCs was accompanied by an increase in the paired-pulse ratio. In addition, analysis of the coefficient of variation suggests the involvement of presynaptic mechanisms in CGP 52432-induced uIPSC facilitation. Paired-pulse stimulation (interstimulus interval = 150 ms) of presynaptic FS cells revealed that the second uIPSC was also facilitated by CGP 52432, which had little effect on the amplitude and interevent interval of miniature IPSCs. In contrast, uEPSCs, responding to all five stimulations of a presynaptic pyramidal cell, were less affected by CGP 52432. These results suggest that a single presynaptic action potential is sufficient to activate GABA(B) autoreceptors and to suppress GABA release in the cerebral cortex.

5-HT(1A) and 5-HT(1B) receptors in the ventrolateral striatum differentially modulate apomorphine-induced jaw movements in rats.

The ability of serotonin 5-HT(1A) and 5-HT(1B) receptors in the ventrolateral striatum to modulate dopamine receptor-mediated jaw movements was investigated in freely moving rats, using a magnet-sensing system combined with an intracerebral drug microinjection technique. Apomorphine (1 mg/kg i.v.) has been found to elicit repetitive jaw movements. Bilateral injections of the 5-HT(1A) receptor agonist 8-OH-DPAT (1 and 4 microg/0.2 microl in each side) into the ventrolateral striatum partially but significantly reduced apomorphine-induced repetitive jaw movements. The 5-HT(1A) receptor antagonist WAY-100635 (1 microg), which alone did not affect the effects of apomorphine, antagonized the inhibitory effects of 8-OH-DPAT (4 microg). Bilateral injections of the 5-HT(1B) receptor agonist CP93129 (1 and 10 microg) also reduced apomorphine-induced repetitive jaw movements in a dose-dependent manner. However, the 5-HT(1B) receptor antagonist GR55562 (1 and 10 microg) did not antagonize the inhibitory effects of CP93129 (10 microg). These results suggest that 5-HT(1A), but not 5-HT(1B), receptors in the ventrolateral striatum play a modulatory role in the production of dopamine receptor-mediated jaw movements.