Biomedical subjects

A Zhou

Publications and source records attributed to A Zhou.

At least 37 records · Page 2Linked to original sources

PubMed2001

Percutaneous balloon angioplasty of coarctation of the aorta in children: 12-year follow-up results.

OBJECTIVE: To evaluate the efficiency of percutaneous balloon angioplasty of coarctation of the aorta in children and discuss its risk factors that can lead to poor long-term results. METHODS: From September 1987 to August 1999, 24 patients underwent 27 balloon angioplasty procedures for native or recurrent coarctation of the aorta at our institution. There were 19 patients with discrete (membranous) coarctation, 4 patients with long-segment and aortic arch hypoplasia, and 1 patient with postoperative recurrence. The balloon diameter was chosen not to exceed the diameter of the aorta proximal to the stenotic site (11.06 +/- 2.80 mm vs 11.78 +/- 3.18 mm), with the chosen diameter two to four times that of the stenotic segment (2.57 +/- 0.68 times). The patients have been followed up for half to twelve years (mean 6.2 +/- 2.8 years). Satisfactory result was defined as a reduction in the pressure gradient across the site of coarctation to < or = 20 mm Hg. RESULTS: The systolic pressure gradient across the coarctation site decreased from 48.17 +/- 14.68 mm Hg to 14.96 +/- 13.12 mm Hg (P < 0.01) and the diameter of the coarctation site increased from 4.66 +/- 2.43 mm to 8.80 +/- 3.32 mm (P < 0.01). Immediate satisfactory results were obtained in 19 patients (79%). Of the 5 patients with unsatisfactory results, 4 had aortic arch hypoplasia and 1 had membranous coarctation. Of the 19 patients with satisfactory results, 18 patients had membranous coarctation and 1 patient had recurrent postoperative coarctation. No aneurysm and other complications had occurred in any patients at the follow-ups. CONCLUSION: Percutaneous balloon angioplasty is an effective treatment alternative to surgery in most patients with recurrent postoperative or native membranous coarctation of the aorta. It should not be recommended for the coarctation of aortic arch hypoplasia.

Adolescent↗

PubMed2001

All-trans retinoic acid in pulmonary vascular structural remodeling in rats with pulmonary hypertension induced by monocrotaline.

OBJECTIVE: To determine whether all-trans retinoic acid (atRA) exerts an inhibitory effect on rats with pulmonary hypertension induced by monocrotaline. METHODS: All rats were given a single subcutaneous injection of either monocrotaline (60 mg/kg) or saline. Monocrotaline-injected rats received either atRA (30 mg.kg-1.day-1) or saline through oral-gastro intubation. On Days 7, 14, 21, and 28 respectively after monocrotaline injection, cardiovascular catheters were inserted to examine the mean pulmonary artery pressure of rats in each group. Meanwhile, the matrix metalloproteinase-1 (MMP-1) mRNA expression and hydroxyproline content in the main pulmonary artery were determined by RT-PCR and chromometry, respectively. RESULTS: The mean pulmonary artery pressure of rats in the model group increased significantly on day 21 and reached a peak on Day 28 compared with the control group (25.7 +/- 4.3 mm Hg vs 15.1 +/- 1.5 mm Hg and 38.5 +/- 6.4 mm Hg vs 16.4 +/- 2.0 mm Hg, P < 0.01). MMP-1 mRNA overexpression was present on Day 14 (0.72 +/- 0.15 vs 0.39 +/- 0.08, P < 0.01) and was rapidly down-regulated on Day 21 and 28 compared with Day 14, but was still higher than that in the control. The hydroxyoroline content of the main pulmonary artery dropped significantly on Day 14 (4.01 +/- 1.13 micrograms/mg vs 5.10 +/- 0.91 micrograms/mg, P < 0.05) and increased significantly on Days 21 and 28 compared with the control. atRA inhibited the MMP-1 mRNA overexpression from Day 14 to Day 28 and reduced the hydroxyproline content (5.59 +/- 0.70 micrograms/mg vs 7.96 +/- 1.13 micrograms/mg and 7.77 +/- 0.96 micrograms/mg vs 9.93 +/- 1.27 micrograms/mg, P < 0.01) and the mean pulmonary artery pressure compared with the model group (19.6 +/- 3.2 mm Hg vs 25.7 +/- 4.3 mm Hg and 26.3 +/- 4.6 mm Hg vs 38.5 +/- 6.4 mm Hg, P < 0.01). CONCLUSION: atRA inhibits MMP-1 overexpression and the accumulation of collagen, which might elicit favorable geometric remodeling in rat pulmonary hypertension induced by monocrotaline.

Animals↗

PubMed2001

[Seroepidemiological analysis of characteristic of hepatitis B virus in children after vaccination in Ningbo].

OBJECTIVE: To understand the immunity of children in Ningbo after hepatitis B vaccination for seven years and to explore the best time for booster. METHODS: One thousand nine hundred and twenty serum samples from children born in 1982 - 1995 were tested for anti-HBs and HBsAg, using RIA. RESULTS: (1) HBsAg positive rate (2.66%) was lower in vaccinated children born in 1992 - 1995 than those unvaccinated (10.92%) born in 1982 - 1995. HBsAg positive rate had a drop of 75.71% (chi(2) = 22.91, P < 0.0001). (2) Anti-HBs positive rates (65.95%) in vaccinated children was much higher than that in unvaccinated children (41.03%) (chi(2) = 113.67, P < 0.0001). (3) It also showed that children's positive rate of HBsAg increased and anti-HBs dropped after 5 - 7 years of vaccination. CONCLUSION: After immunization of hepatitis B vaccine for 7 years, high immunity and low infection rate of HB in children it appeared in Ningbo. However it is necessary to further study the reason causing the increase of HBsAg positive rate and/or deerease of anti-HBs positive rate, and the suitable time frame of boostering, after 4 or 5 years of primary vaccination.

China↗

PubMed2001

[Human papilloma virus infection and expression of p16 protein in laryngeal papilloma and laryngeal carcinoma].

OBJECTIVE: To evaluate the role of human papilloma virus (HPV) infection and inactivation of p16 gene in laryngeal papilloma (LP) and laryngeal squamous cell carcinoma (LC). METHODS: HPV consensus primers direct in situ polymerase chain reaction (ISPCR) and immunohistochemical method were applied to detect the presence of HPV genomes (1, 6, 8, 11, 13, 16, 18, 30, 31, 32, 33, 45, 51) and the expression of p16 protein respectively in 93 cases of formalin-fixed, paraffin-imbedded specimens, which contained 46 cases of LPs [adult-onset laryngeal papilloma (ALP) 21, juvenile-onset laryngeal papilloma (JLP)25], 26 cases of LCs, 6 cases of normal tissues adjacent to carcinoma, and 15 cases of vocal noduli. RESULTS: (1) The difference of positive rates of HPV-DNA in JLP group (84%, 21/25) and other groups were statistically significant (chi 2 test, P < 0.05). The difference of positive rates of HPV-DNA in ALPs(38.1%, 8/21), in LCs(19.2%, 5/26), in vocal noduli(0%, 0/15), and in normal tissues adjacent to carcinoma(0%, 0/6) were not significant statistically (chi 2 test or Fisher's exact probability test, P > 0.05). (2) The positive rates of expression of p16 protein in ALP group(57.1%, 12/21) and LC group(38.5%, 10/26) were significantly lower than that in vocal nodule group(93.3%, 14/15), in JLP group(88%, 22/25), and in normal tissues adjacent to carcinoma group (100%, 6/6) (chi 2 test or Fisher's exact probability test, P > 0.05). There were no significant differences of positive rates of expression of p16 protein between ALP group and LC group, and between JLP group and vocal nodule group (chi 2 test, P > 0.05). (3) In LPs, the difference of positive rates of p16 protein expression between HPV positive cases and HPV negative cases was significant statistically (chi 2 test, P < 0.05). In LCs, there was no difference in p16 protein expression rate between the two teams(Fisher exact probability test, P > 0.05). CONCLUSION: The pathogenesis of JLP is closely associated with HPV infection and not associated with the inactivation of p16 gene. Conversely, the pathogenesis of ALP and LC is associated with the inactivation of p16 gene and not associated with the HPV infection.

Adult↗

PubMed2000

Polymerization of plasminogen activator inhibitor-1.

The activity of the serine proteinase inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) is controlled by the intramolecular incorporation of the reactive loop into beta-sheet A with the generation of an inactive latent species. Other members of the serpin superfamily can be pathologically inactivated by intermolecular linkage between the reactive loop of one molecule and beta-sheet A of a second to form chains of polymers associated with diverse diseases. It has long been believed that PAI-1 is unique among active serpins in that it does not form polymers. We show here that recombinant native and latent PAI-1 spontaneously form polymers in vitro at low pH although with distinctly different electrophoretic patterns of polymerization. The polymers of both the native and latent species differ from the typical loop-A-sheet polymers of other serpins in that they readily dissociate back to their original monomeric form. The findings with PAI-1 are compatible with different mechanisms of linkage, each involving beta-strand addition of the reactive loop to s7A in native PAI-1 and to s1C in latent PAI-1. Glycosylated native and latent PAI-1 can also form polymers under similar conditions, which may be of in vivo importance in the low pH environment of the platelet.

Amino Acid Sequence↗

PubMed2000

Detection and analysis of Bacillus subtilis growth with piezoelectric quartz crystal impedance based on starch hydrolysis.

A piezoelectric quartz crystal (PQC) impedance method based on the alpha-amylase-catalyzed hydrolysis of starch present in a culture medium has been developed for in situ monitoring of the whole growth process of Bacillus subtilis and the variation in the activity of alpha-amylase during bacterial growth. An S-shaped response behavior was observed for Deltaf(0), and simultaneously inverse S-shaped responses were found for DeltaR(1) and DeltaL(1). The ratio of DeltaR(1) to Deltaf(0) or DeltaL(1) coincided well with that calculated from Martin's equations reflecting the solution density-viscosity effect, suggesting that the continuing change in liquid loading onto the PQC surface causes significant variation in Deltaf(0), DeltaR(1), and DeltaL(1). Bacterial growth equations were derived from the kinetics of the enzyme-catalyzed hydrolysis of starch, which fit well with the experimental responses of Deltaf(0), DeltaR(1), and DeltaL(1). Kinetic parameters of bacterial growth, including the asymptote (A), the maximum specific growth rate (microm), and the lag time (lambda), were obtained and were in good agreement with those obtained from the pour plate count method. The variation in the activity of alpha-amylase exhibited peak-type behavior with its maximum value at the later stage of the log phase. In addition, the influence of initial bacterial concentration was also investigated.

Algorithms↗

PubMed2000

Study of the Adsorption of Glutathione on a Gold Electrode by Using Electrochemical Quartz Crystal Impedance, Electrochemical Impedance Spectroscopy, and Cyclic Voltammetry.

Adsorption of a biological peptide, glutathione, on a gold electrode was studied by using electrochemical quartz crystal impedance (EQCI), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. The time courses of responses of piezoelectric and electrochemical impedance parameters were simultaneously obtained during the adsorption processes of the two forms of peptide, oxidized and reduced glutathione. It was found that the frequency curve due to the oxidized glutathione (GSSG) adsorption exhibited a character of a sum of two exponential functions. For reduced glutathione (GSH), the frequency adsorption curve could be expressed by a first-order reaction kinetic model and the corresponding kinetic parameters at different amounts of GSH were obtained. The heterogeneous charge-transfer rate constants of ferricyanide/ferrocyanide before and after the peptide adsorption were determined by CV and EIS methods, respectively. According to the simple equivalent electric network of the electrochemical interface, the electrochemical impedance parameters were also obtained. The results showed that the proposed method should be found in wider applications in interfacial biochemistry studies since these combined techniques have advantages in real time multidimensional information including electrochemical and electrochemical impedance parameters. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Determination of the binding parameters of drug to protein by equilibrium dialysis/piezoelectric quartz crystal sensor.

A novel method, equilibrium dialysis/piezoelectric quartz crystal sensor, applied to determine the binding parameters of diethyldithiocarbamate to human plasma protein is proposed. Based on the investigation of the equilibrium reaction for the binding of drug to protein, the related theoretical equations for this binding were derived. By monitoring the frequency responses of a copper-plated piezoelectric quartz crystal sensor to drug in and out of a dialysis membrane after equilibrium, the binding parameters were determined, i.e., 0.375 micromol g(-1) for beta(p), 6.496 microM for K(dp), 141.99 L mmol(-1) for K(p), and 0.043 for N. These values were in good agreement with reference values. It was found that this method may have application for studying the characteristics of the interaction between other drugs and proteins.

Biosensing Techniques↗

PubMed2000

Transcriptional control of the human plasma membrane phospholipid scramblase 1 gene is mediated by interferon-alpha.

Interferons (IFNs) mediate their diverse biologic activities through induction of the expression of multiple genes. Whereas the mode of action of certain of these IFN-regulated genes has been well characterized, most of the molecular and cellular events underlying the constellation of biologic responses to the IFNs remain unresolved. This study showed that the newly identified PLSCR1 gene for phospholipid scramblase, previously implicated in remodeling of plasma membrane phospholipids, is regulated at the transcriptional level by IFN-alpha. Analysis of 5' flanking genomic sequence in reporter constructs showed that transcriptional control of PLSCR1 was entirely regulated by a single IFN-stimulated response element located in the first exon. A similar induction of PLSCR1 by IFN-alpha2a was also observed in a variety of other human tumor cell lines as well as in human umbilical vein endothelial cells. In these cell lines, the marked IFN-alpha2a-induced increase in PLSCR1 protein expression, ranging as high as 10-fold above basal levels, was not accompanied by increased cell surface exposure of phosphatidylserine, suggesting that remodeling of the cell surface requires both exposure to IFN and a second yet-to-be identified event to stimulate plasma membrane phospholipid scramblase activity and to mobilize phosphatidylserine to the cell surface. (Blood. 2000;95:2593-2599)

Carrier Proteins↗

PubMed2000

Analysis and origins of the human and mouse RNase L genes: mediators of interferon action.

The 2',5'-oligoadenylate-activated enzyme, RNase L, is an endoribonuclease implicated in the antiviral and apoptotic activities of interferons. To probe the genetics of the 2-5A system, the human and mouse genes were cloned, characterized, and compared. The first coding exon of both genes encodes the regulatory regions of RNase L, 67-70% of the proteins including nine ankyrin repeats, the 2-5A binding domain, and several protein kinase homology motifs. In contrast, the coding sequence for the ribonuclease domain in the mouse and human gene is divided among three exons. The transcriptional start site of the human RNase L gene was located in noncoding exon I by primer extension analysis. A complete coding sequence of mouse RNase L was obtained revealing a 735-amino acid protein with 64% identity to human RNase L. A hypothesis is presented concerning the evolutionary relationship of RNase L to both an ankyrin repeat protein kinase and the kinase-endoribonuclease. IRE1, that mediates the unfolded protein response.

5' Untranslated Regions↗

PubMed2000

Development of oxidized odor and volatile aldehydes in fermented cucumber tissue exposed to oxygen.

Changes in volatile compounds in fermented cucumber tissue during exposure to oxygen were investigated by purge and trap sampling, followed by GC-MS. Hexanal and a series of trans unsaturated aldehydes, (E)-2-pentenal, (E)-2-hexenal, (E)-2-heptenal, and (E)-2-octenal, increased in fermented cucumber slurries exposed to oxygen. Sensory evaluation of oxidized odor was correlated with the increase in aldehyde concentrations. Other identified volatile components present after fermentation did not show major changes during exposure to oxygen. There was no decrease in the formation of aldehydes in fermented cucumber samples that were heated to inactivate enzymes before exposure to oxygen. These results indicated that the formation of aldehydes in oxygen was due to nonenzymatic reactions.

Aldehydes↗

PubMed2000

Inhibition of formation of oxidative volatile components in fermented cucumbers by ascorbic acid and turmeric.

Two naturally occurring antioxidants, ascorbic acid and turmeric, were effective in inhibiting formation of hexanal, (E)-2-penenal, (E)-2-hexenal, (E)-2-heptenal, and (E)-2-octenal when slurries of fermented cucumber tissue were exposed to oxygen. Added ascorbic acid prevented formation of most of these oxidative aldehydes at 175 ppm or greater. Turmeric, which is used commercially as a yellow coloring in cucumber pickle products, was found to almost completely prevent aldehyde formation at 40 ppm.

Ascorbic Acid↗

PubMed2000

Plasminogen activator inhibitor-1 fused with erythropoietin (EPO) mimetic peptide (EMP) enhances the EPO activity of EMP.

Erythropoietin (EPO) mimetic peptide (EMP) encoding sequence was inserted into the gene of plasminogen activator inhibitor-1 (PAI-1) between Ala348 and Pro349 (P2'-P3'), generating a novel gene, PAI-1/EMP (PMP). This was cloned into pET32a expression vector, fused with TrxA peptide in the vector, and a 63-kDa protein was expressed in inclusion bodies with an expression level >50%. The TrxA/PMP protein was purified by Ni-NTA-agarose metal-ligand affinity chromatography to a purity >90%, showing a single, silver-stained band on SDS-PAGE. Using a reticulocyte counting assay, the EPO activity of PMP was determined to be 5,000 IU/mg, 2,500-fold that of EMP.

Amino Acid Sequence↗

PubMed2000

Effect of deficiency of the double-stranded RNA-dependent protein kinase, PKR, on antiviral resistance in the presence or absence of ribonuclease L: HSV-1 replication is particularly sensitive to deficiency of the major IFN-mediated enzymes.

Control of viral replication by interferon (IFN) is thought to be principally mediated by the 2',5'-oligoadenylate synthetase (OAS)/RNAse L, double-stranded dependent protein kinase (PKR), and myxovirus resistance protein (Mx) pathways. In this study, we monitored the constitutive and IFN-induced antiviral activity in mouse embryo fibroblasts lines derived from mice with targeted disruption of either PKR or PKR/RNAse L genes. At high multiplicity of infection (moi = 10), the absence of PKR had no effect on replication of vesicular stomatitis virus (VSV) but moderately enhanced encephalomyocarditis virus (EMCV) growth and greatly increased replication of herpes simplex virus-1 (HSV-1). Replication of EMCV, HSV-1, and VSV was modestly higher in PKR-/- RNAse L-/- fibroblasts when compared with control cells. Although the antiviral action of IFN-alpha was unaffected by the absence of PKR, IFN action was significantly impaired in the double knockout cells but was dependent on the stage of the virus cycle. At early stages, it appeared that anti-EMCV and anti-HSV-1 action of IFN-alpha was significantly compromised, although weak residual antiviral activity was seen. The action of IFN-alpha against VSV was specifically compromised at a late stage of virus replication. The results showed that PKR is an important mediator in constitutive resistance against HSV-1 and that RNAse L is also necessary for the full antiviral activity of IFN against a variety of viruses. These results supported the existence of novel pathways aimed toward specific stages of the virus life cycle.

Animals↗

PubMed2000

Caspase-dependent apoptosis by 2',5'-oligoadenylate activation of RNase L is enhanced by IFN-beta.

The 2',5'-oligoadenylate (2-5A) system is an interferon (IFN)-regulated RNA decay pathway that provides innate immunity against viral infections. The biologic action of the 2-5A system is mediated by RNase L, an endoribonuclease that becomes enzymatically active after binding to 2-5A. RNase L is also implicated in mediating apoptosis in response to both viral and nonviral inducers. To study the cellular effects of RNase L activation directly, 2-5A was transfected into the human ovarian cancer cell line, Hey1B. Activation of RNase L by 2-5A resulted in specific 18S rRNA cleavage and induction of apoptosis, as measured by TUNEL and annexin V binding assays. In contrast, the dimeric form of 2-5A, ppA2'p5'A, neither activated RNase L nor caused apoptosis. Treatment with IFN-beta prior to 2-5A transfection enhanced cellular RNase L levels (< or = 2.2-fold) and increased the proportion of cells undergoing apoptosis (by < or =40%). However, rRNA cleavages after 2-5A transfections were not enhanced by IFN-beta pretreatments, indicating that basal levels of RNase L were sufficient for this activity. Apoptosis in response to RNase L activation was accompanied by cytochrome c release from mitochondria. Induction of apoptosis by either 2-5A alone or by the combination of 2-5A and IFN-beta was effectively blocked with either the pancaspase inhibitor, Z-VAD-fmk, or with the caspase 3 inhibitor, DEVD-fmk. Therefore, activation of RNase L by 2-5A leads to cytochrome c release into the cytoplasm and then to caspase activation and apoptosis. These results suggest potential uses for 2-5A in augmenting the anticancer activities of IFN.

Adenine Nucleotides↗

PubMed2000

Thyroid organoid formation in simulated microgravity: influence of keratinocyte growth factor.

The generation of artificial human thyroid tissues in suspension (low-shear environment, present in simulated microgravity [MG] and generated by a rotary cell culture system [RCCS]), was enhanced by increasing medium kinematic viscosity with a (3% v/v) suspension of extracellular matrix (basement membrane extract [BME]) in serum-free medium to generate artificial human thyroid organoids. Recombinant human keratinocyte growth factor (KGF, 7 ng/mL) facilitated human thyrocyte aggregation and three-dimensional (3-D) differentiation. There was an MG-associated decrease in extractable DNA that was reversed after addition of keratinocyte growth factor (KGF). In simulated MG, the increase in extractable DNA after KGF addition was up to 170% over non-KGF control cultures. In contrast, monolayer cultures in unit gravity showed a maximum DNA increase of 39% after KGF addition. Morphologically, differentiated thyroid neofollicles displayed polarization and were located in close proximity after 2 weeks of culture. Immunogold labeling with antibody to human thyroglobulin (Tg) revealed staining of follicular lumina and secretory vesicles, and a time-dependent increase in human Tg was detected in the culture media. Culture under simulated MG thus allowed direct visualization of KGF-facilitated thyrocyte/extracellular matrix interaction. Such artificial human thyroid organoids-generated in MG and in the presence of KGF-structurally resembled natural thyroid tissue. The above findings may have implications for autoimmune thyroid disease where KGF (if, for example, secreted locally by intraepithelial gammadelta T cells among other cells) may contribute to thyroid cell growth.

Cell Adhesion Molecules↗

PubMed2000

RNase L-independent specific 28S rRNA cleavage in murine coronavirus-infected cells.

We characterized a novel 28S rRNA cleavage in cells infected with the murine coronavirus mouse hepatitis virus (MHV). The 28S rRNA cleavage occurred as early as 4 h postinfection (p.i.) in MHV-infected DBT cells, with the appearance of subsequent cleavage products and a decrease in the amount of intact 28S rRNA with increasing times of infection; almost all of the intact 28S rRNA disappeared by 24 h p.i. In contrast, no specific 18S rRNA cleavage was detected in infected cells. MHV-induced 28S rRNA cleavage was detected in all MHV-susceptible cell lines and all MHV strains tested. MHV replication was required for the 28S rRNA cleavage, and mature cytoplasmic 28S rRNA underwent cleavage. In certain combination of cells and viruses, pretreatment of virus-infected cells with interferon activates a cellular endoribonuclease, RNase L, that causes rRNA degradation. No interferon was detected in the inoculum used for MHV infection. Addition of anti-interferon antibody to MHV-infected cells did not inhibit 28S rRNA cleavage. Furthermore, 28S rRNA cleavage occurred in an MHV-infected mouse embryonic fibroblast cell line derived from RNase L knockout mice. Thus, MHV-induced 28S rRNA cleavage was independent of the activation of RNase L. MHV-induced 28S rRNA cleavage was also different from apoptosis-related rRNA degradation, which usually occurs concomitantly with DNA fragmentation. In MHV-infected 17Cl-1 cells, 28S rRNA cleavage preceded DNA fragmentation by at least 18 h. Blockage of apoptosis in MHV-infected 17Cl-1 cells by treatment with a caspase inhibitor did not block 28S rRNA cleavage. Furthermore, MHV-induced 28S rRNA cleavage occurred in MHV-infected DBT cells that do not show apoptotic signs, including activation of caspase-3 and DNA fragmentation. Thus, MHV-induced 28S rRNA cleavage appeared to differ from any rRNA degradation mechanism described previously.

Animals↗

PubMed2000

Activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase by double-stranded RNA and encephalomyocarditis virus: involvement of RNase L, protein kinase R, and alternative pathways.

Double-stranded RNA (dsRNA) accumulates in virus-infected mammalian cells and signals the activation of host defense pathways of the interferon system. We describe here a novel form of dsRNA-triggered signaling that leads to the stimulation of the p38 mitogen-activated protein kinase (p38 MAPK) and the c-Jun NH(2)-terminal kinase (JNK) and of their respective activators MKK3/6 and SEK1/MKK4. The dsRNA-dependent signaling to p38 MAPK was largely intact in cells lacking both RNase L and the dsRNA-activated protein kinase (PKR), i. e., the two best-characterized mediators of dsRNA-triggered antiviral responses. In contrast, activation of both MKK4 and JNK by dsRNA was greatly reduced in cells lacking RNase L (or lacking both RNase L and PKR) but was restored in these cells when introduction of dsRNA was followed by inhibition of ongoing protein synthesis or transcription. These results are consistent with the notion that the role of RNase L and PKR in the activation of MKK4 and JNK is the elimination, via inhibition of protein synthesis, of a labile negative regulator(s) of the signaling to JNK acting upstream of SEK1/MKK4. In the course of these studies, we identified a long-sought site of RNase L-mediated cleavage in the 28S rRNA, which could cause inhibition of translation, thus allowing the activation of JNK by dsRNA. We propose that p38 MAPK is a general participant in dsRNA-triggered cellular responses, whereas the activation of JNK might be restricted to cells with reduced rates of protein synthesis. Our studies demonstrate the existence of alternative (RNase L- and PKR-independent) dsRNA-triggered signaling pathways that lead to the stimulation of stress-activated MAPKs. Activation of p38 MAPK (but not of JNK) was demonstrated in mouse fibroblasts in response to infection with encephalomyocarditis virus (ECMV), a picornavirus that replicates through a dsRNA intermediate. Fibroblasts infected with EMCV (or treated with dsRNA) produced interleukin-6, an inflammatory and pyrogenic cytokine, in a p38 MAPK-dependent fashion. These findings suggest that stress-activated MAPKs participate in mediating inflammatory and febrile responses to viral infections.

Animals↗