Role of protein kinase Cβ in phorbol ester-induced c-fos gene expression in neurons of normotensive and spontaneously hypertensive rat brains

Time-tagged ticker tapes for intracellular recordings

Recording transcriptional histories of a cell would enable deeper understanding of cellular developmental trajectories and responses to external perturbations. Here we describe an engineered protein fiber that incorporates diverse fluorescent marks during its growth to store a ticker tape-like history. An embedded HaloTag reporter incorporates user-supplied dyes, leading to colored stripes that map the growth of each individual fiber to wall clock time. A co-expressed eGFP tag driven by a promoter of interest records a history of transcriptional activation. High-resolution multi-spectral imaging on fixed samples reads the cellular histories, and interpolation of eGFP marks relative to HaloTag timestamps provides accurate absolute timing. We demonstrate recordings of doxycycline-induced transcription in HEK cells and cFos promoter activation in cultured neurons, with a single-cell absolute accuracy of 30-40 minutes over a 12-hour recording. The protein-based ticker tape design we present here could be generalized to achieve massively parallel single-cell recordings of diverse physiological modalities.

Benefits and Challenges of Jatropha Meal as Novel Biofeed for Animal Production

Jatropha curcas L. has gained importance as a source of seed oil for biodiesel production. The meal contained about 60% protein with a good balance of essential amino acids, containing various bioactive compounds, including saponins, phytic acids, trypsin inhibitors, lectins, phenolics, and flavonoids, which render it as a potential biofeed for animal production. The Jatropha meal demonstrated various biological activities, including antioxidant, antibacterial, and anti-inflammatory effects which enhance its property as a bio-feed. The levels of these bioactive compounds in the seeds are dependent on the genotypes. The J. curcas possessed different varieties which are either toxic or non-toxic according to the presence of phorbol esters. The presence of phorbol esters in the meal confirmed the toxic variety of Jatropha resulting in the limited application of meal as a biofeed. The Jatropha meal devoid of phorbol esters could be applied as a biofeed in the animal production industry, and for the toxic varieties, various techniques such as physicochemical and biological treatments have been introduced to the industry to remove the phorbol esters from Jatropha meal. Several studies employing various cells and animals confirmed the toxicity of the phorbol esters. The molecular mechanism of action of phorbol esters is through up-regulation of PKC-β II gene, overexpression of down-stream proto-oncogenes resulted in inflammation and oxidative stress ending by apoptotic cell death. Despite the presence of valuable bioactive compounds in the Jatropha meal, its nutritional application is not recommended unless the phorbol esters are completely removed.

Interactions between astrocytes and neurons in the brainstem involved in restraint water immersion stress-induced gastric mucosal damage

Restraint water-immersion stress (RWIS) is considered a compound stress model as it includes both psychological and physical stimulation. Studies have shown that neurons are involved in RWIS, but the role of astrocytes in RWIS has not been reported as yet. Here, we tested our hypothesis that astrocytes are involved in RWIS and interact with neurons in the brainstem to regulate gastric mucosal damage induced by RWIS. RWIS of different durations (0.5, 1, 2, 3, and 5 h) induced significant gastric mucosal damage and activated astrocytes by increasing the expression of glial fibrillary acidic protein and neurons, as indicated by the Fos expression in the nucleus of solitary tract and the dorsal motor nucleus of the vagus. Intracerebroventricular administration of both astroglial toxin L-α-aminoadipate and c-fos antisense oligodeoxy nucleotides reduced RWIS-induced gastric mucosal damage. Immunohistochemistry results showed that L-α-aminoadipate decreased the activation of both astrocytes and neurons by RWIS. Similarly, antisense oligodeoxy nucleotides significantly suppressed activation of both neurons and astrocytes induced by RWIS. Our data showed that astrocytic and neuronal activations may be closely related to the gastric mucosal damage induced by RWIS through reciprocal 'crosstalk'. This study suggests that an intervention targeting this interaction may offer some novel therapeutic strategies for gastric ulcers.

Hypothalamic Astrocytes Respond to Gastric Mucosal Damage Induced by Restraint Water-Immersion Stress in Rat

Restraint water-immersion stress (RWIS), a compound stress model, includes both psychological and physical stimulation. Studies have shown that neurons in the hypothalamus are involved in RWIS, but the role of astrocytes and the interactions between astrocytes and neurons in RWIS are not clear. Here, we tested our hypothesis that hypothalamus astrocytes are involved in RWIS and interact with neurons to regulate gastric mucosal damage induced by RWIS. The expression of Glial fibrillary acidic protein (GFAP) and c-Fos in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) significantly increased following the RWIS. GFAP and c-Fos expression are similar in the temporal pattern, peaked at 1 h after the RWIS, then reduced gradually, and reached a maximal level again at 5 h which show “double-peak” characteristics. Intracerebroventricular administration of astroglial toxin L-a-aminoadipate (L-AA) and c-Fos antisense oligodeoxy nucleotides (ASO) both decreased RWIS-induced gastric mucosal damage. Results of immunohistochemistry assay revealed that both L-AA and ASO decreased the activation of astrocytes and neurons in the hypothalamus by RWIS. These results showed that hypothalamus neuron-astrocyte “network” involved in gastric mucosal damage induced by RWIS. This study may offer theoretical basis for some novel therapeutic strategies for RWIS-induced gastric ulcers.

Mechanisms of brain renin angiotensin system-induced drinking and blood pressure: importance of the subfornical organ

It is critical for cells to maintain a homeostatic balance of water and electrolytes because disturbances can disrupt cellular function, which can lead to profound effects on the physiology of an organism. Dehydration can be classified as either intra- or extracellular, and different mechanisms have developed to restore homeostasis in response to each. Whereas the renin-angiotensin system (RAS) is important for restoring homeostasis after dehydration, the pathways mediating the responses to intra- and extracellular dehydration may differ. Thirst responses mediated through the angiotensin type 1 receptor (AT1R) and angiotensin type 2 receptors (AT2R) respond to extracellular dehydration and intracellular dehydration, respectively. Intracellular signaling factors, such as protein kinase C (PKC), reactive oxygen species (ROS), and the mitogen-activated protein (MAP) kinase pathway, mediate the effects of central angiotensin II (ANG II). Experimental evidence also demonstrates the importance of the subfornical organ (SFO) in mediating some of the fluid intake effects of central ANG II. The purpose of this review is to highlight the importance of the SFO in mediating fluid intake responses to dehydration and ANG II.

Inhibition of matrix metalloproteinase-9 expression by docosahexaenoic acid mediated by heme oxygenase 1 in 12-O-tetradecanoylphorbol-13-acetate-induced MCF-7 human breast cancer cells

Matrix metalloproteinase-9 (MMP-9) plays a crucial role in tumor metastasis. Previous studies showed that polyunsaturated fatty acids exhibit an anti-cancer effect in various human carcinoma cells, but the effect of docosahexaenoic acid (DHA) and linoleic acid (LA) on metastasis of breast cancer cells is not fully clarified. We studied the anti-metastasis potential of DHA and LA in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced MCF-7 cells. We found that TPA (100 ng/ml) induced MMP-9 enzyme activity both dose- and time-dependently, and 200 μM DHA and LA significantly inhibited MMP-9 mRNA and protein expression, enzyme activity, cell migration, and invasion. Treatment with PD98059 (10 μM), wortmannin (10 μM), and GF109203X (0.5 μM) decreased TPA-induced MMP-9 protein expression and enzyme activity. TPA-induced activation of ERK1, Akt, and PKCδ was attenuated by DHA, whereas LA attenuated only ERK1 activation. GF109203X also suppressed ERK1 activation. EMSA showed that DHA, LA, PD98059, and wortmannin decreased TPA-induced NF-κB and AP-1 DNA-binding activity. Furthermore, DHA rather than LA dose-dependently increased HO-1 expression. HO-1 siRNA alleviated the inhibition by DHA of TPA-induced MMP-9 protein expression and enzyme activity in MCF-7 cells, and HO-1 knockdown reversed the DHA inhibition of cell migration. These results suggest that DHA and LA have both similar and divergent signaling pathways in the suppression of TPA-induced MCF-7 metastasis.

Artemisinin inhibits extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinase-9 expression via a protein kinase Cδ/p38/extracellular signal-regulated kinase pathway in phorbol myristate acetate-induced THP-1 macrophages

1. Overexpression of extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinases (MMPs) by monocytes/macrophages has been proposed to play a significant role in atherosclerotic plaque progression and rupture. The aim of the present study was to explore whether artemisinin, a natural extract from Artemisia annua, could decrease EMMPRIN and MMP-9 expression in phorbol myristate acetate (PMA)-induced macrophages by regulating the protein kinase (PK) Cδ/c-Jun N-terminal kinase (JNK)/p38/extracellular signal-regulated kinase (ERK) pathway. 2. Human monocytic THP-1 cells were pretreated with 20-80 μg/mL artemisinin for 4 h or 1-10 μmol/L rottlerin for 1 h prior to stimulation with PMA (100 nmol/L) for another 48 h. Cells were collected to analyse the induction of EMMPRIN and MMP-9. Upstream pathway analysis using the PKCδ inhibitor rottlerin detected activation of the PKCδ/JNK/p38/ERK pathway. 3. Artemisinin (20-80 μg/mL) significantly inhibited the induction of EMMPRIN and MMP-9 at both the transcriptional and translational levels in a dose-dependent manner in PMA-induced macrophages. In addition, artemisinin (20-80 μg/mL) strongly blocked PKCδ/JNK/p38/ERK MAPK phosphorylation. The PKCδ inhibitor rottlerin (1-10 μmol/L) also significantly inhibited JNK/p38/ERK phosphorylation and decreased EMMPRIN and MMP-9 mRNA and protein expression. 4. The results of the present study suggest that artemisinin inhibits EMMPRIN and MMP-9 expression and activity by suppressing the PKCδ/ERK/p38 cascade in PMA-induced macrophages.

hnRNP-R regulates the PMA-induced c-fos expression in retinal cells

This study focused on the function of hnRNP-R in the regulation of c-fos expression. We demonstrated that hnRNP-R accelerated the rise and decline phases of c-fos mRNAs and Fos proteins, allowing PMA to induce an augmented pulse response of c-fos expression. Then, we examined the role of the c-fos-derived AU-rich element (ARE) in hnRNP-R-regulated mRNA degradation. Studies with the ARE-GFP reporter gene showed that hnRNP-R significantly reduced the expression of GFP with an inserted ARE. Moreover, immunoprecipitation-RT-PCR analysis demonstrated that in R28 cells and rat retinal tissues, the c-fos mRNA was co-immunoprecipitated with hnRNP-R. These findings indicate that hnRNP-R regulates the c-fos expression in retinal cells, and that the ARE of c-fos mRNAs contributes to this regulation.

Regulation of c-fos, c-jun and c-myc Gene Expression by Angiotensin II in Primary Cultured Rat Astrocytes: Role of ERK1/2 MAP Kinases

We have previously shown that angiotensin II (Ang II) stimulates astrocyte growth through activation of ERK1/2 mitogen activated protein (MAP) kinases. In the current study, we determined whether Ang II stimulates the expression of c-fos, c-jun and c-myc in brainstem astrocyte cultures. Reverse transcriptase-PCR analysis showed c-fos, c-jun, and c-myc mRNAs were induced by Ang II. The EC50 values for Ang II stimulation of c-fos, c-jun and c-myc were 1.3, 1.68 and 1.4 nM, respectively. Ang II (100 nM) induced peak stimulation for all genes by 45 min followed by a gradual decline. Inhibition of ERK1/2 by PD98059 attenuated Ang II-induced c-fos and c-myc mRNA expression (by 75% and 100%, respectively) but was ineffective in preventing Ang II induction of c-jun. These studies show for the first time in brainstem astrocytes that Ang II induces the expression of c-fos, c-myc and c-jun, and showed that ERK1/2 mediate Ang II stimulation of c-fos and c-myc. These data implicate the ERK1/2 MAP kinase pathway as a divergent point in controlling Ang II stimulation of immediate early response genes in the central nervous system.

PKC delta-isoform translocation and enhancement of tonic contractions of gastrointestinal smooth muscle

PKC is involved in mediating the tonic component of gastrointestinal smooth muscle contraction in response to stimulation by agonists for G protein-coupled receptors. Here, we present pharmacological and immunohistochemical evidence indicating that a member of the novel PKC isoforms, PKC-delta, is involved in maintaining muscarinic receptor-coupled tonic contractions of the guinea pig ileum. The tonic component of carbachol-evoked contractions was enhanced by an activator of conventional and novel PKCs, phorbol 12,13-dibutyrate (PDBu; 200 nM or 1 microM), and by an activator of novel PKCs, ingenol 3,20-dibenzoate (IDB; 100 or 500 nM). Enhancement was unaffected by concentrations of bisindolylmaleimide I (BIM-I; 22 nM) that block conventional PKCs or by a PKC-epsilon-specific inhibitor peptide but was attenuated by higher doses of BIM-I (2.2 microM). Relevant proteins were localized at a cellular and subcellular level using confocal analysis. Immunohistochemical staining of the ileum showed that PKC-delta was exclusively expressed in smooth muscles distributed throughout the layers of the gut wall. PKC-epsilon immunoreactivity was prominent in enteric neurons but was largely absent from smooth muscle of the muscularis externa. Treatment with PDBu, IDB, or carbachol resulted in a time- and concentration-dependent translocation of PKC-delta from the cytoplasm to filamentous structures within smooth muscle cells. These were parallel to, but distinct from, actin filaments. The translocation of PKC-delta in response to carbachol was significantly reduced by scopolamine or calphostin C. The present study indicates that the tonic carbachol-induced contraction of the guinea pig ileum is mediated through a novel PKC, probably PKC-delta.

[Mechanisms of hypertension in the central nervous system]

This article reviews studies by the author on central mechanisms of hypertension. Spontaneously hypertensive rats (SHR) have been developed as a rat model of genetic hypertension, and central acetylcholine has been implicated in hypertension in SHR. The rostral ventrolateral medulla (RVL), a major source of efferent sympathetic activity, has cholinergic pressor systems. The release of acetylcholine is enhanced in the RVL of SHR, leading to hypertension. The alteration of the RVL cholinergic system in SHR results from enhanced angiotensin systems in the anterior hypothalamic area (AHA). Angiotensin II-sensitive neurons are present in the AHA and they are tonically activated by endogenous angiotensins. The basal activity of AHA angiotensin II-sensitive neurons is enhanced in SHR, mainly due to enhanced sensitivity of AHA neurons to angiotensin II. The AHA angiotensin system is also responsible for hypertension induced by emotional stress and central Na(+) increases. These findings suggest that the AHA angiotensin system may play a critical role in the development of hypertension.