The Role of PPARγ in Hyperglycemia-induced Deleterious Effect on Chondrocytes

Abstract Aims: There is a well-established link between OA and diabetes, and study have shown that hyperglycemia might play an important role in the occurrence and development of OA. Accumulative evidence suggested that PPARγ was involved in AGEs-related disease, including diabetes and OA. The study was designed to investigate the effects of hyperglycemia on the expression of PPARγ in chondrocytes and whether PPARγ agonist pioglitazone had a chondroprotective effect.Main methods: Primary human chondrocytes were incubated with different concentration of glucose medium(5.5mM-30mM) in the presence or absence of PPARγ agonist pioglitazone. The AGEs formation level in chondrocytes culture medium was detected by AGEs specific ELISA kits. The expression of IL-1, MMP-13, TNF-α, PPARγ was determined by western blotting and real-time PCR.Key findings: The AGEs fomation level was time-dependently and dose-dependently increased in chondrocyte culture media. Hyperglycemia could enhance the expression of IL-1β, TNF-α, MMP-13, but the level of PPARγ was decreased in a time-dependent and dose-dependent manner, which was inhibited by PPARγ agonist pioglitazone. Noteworthy, the maximum effect was found to at 20mM glucose medium for 24h.Significance: Hyperglycemia could increase the AGEs formation level and induce inflammatory response and matrix degradation reaction in chondrocytes. PPARγ agonists pioglitazone had a chondroprotective effect via inhibit inflammatory response and matrix degradation reaction. PPARγ could be a potential target for pharmacologic intervention in the treatment of diabetic-induced OA.

Download Full-text

PPARγ inhibits airway epithelial cell inflammatory response through a MUC1-dependent mechanism

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00360.2011 ◽

2012 ◽

Vol 302 (7) ◽

pp. L679-L687 ◽

Cited By ~ 11

Author(s):

Yong Sung Park ◽

Erik P. Lillehoj ◽

Kosuke Kato ◽

Choon Sik Park ◽

Kwang Chul Kim

Keyword(s):

Epithelial Cells ◽

Culture Media ◽

A549 Cells ◽

Luciferase Reporter ◽

Muc1 Expression ◽

Mrna Levels ◽

Airway Epithelial ◽

Pparγ Agonist ◽

Tnf Α ◽

Primary Mouse

This study was conducted to examine the relationship between the peroxisome proliferator-associated receptor-γ (PPARγ) and MUC1 mucin, two anti-inflammatory molecules expressed in the airways. Treatment of A549 lung epithelial cells or primary mouse tracheal surface epithelial (MTSE) cells with phorbol 12-myristate 13-acetate (PMA) increased the levels of tumor necrosis factor (TNF)-α in cell culture media compared with cells treated with vehicle alone. Overexpression of MUC1 in A549 cells decreased PMA-stimulated TNF-α levels, whereas deficiency of Muc1 expression in MTSE cells from Muc1 null mice increased PMA-induced TNF-α levels. Treatment of A549 or MTSE cells with the PPARγ agonist troglitazone (TGN) blocked the ability of PMA to stimulate TNF-α levels. However, the effect of TGN required the presence of MUC1/Muc1, since no differences in TNF-α levels were seen between PMA and PMA plus TGN in MUC1/Muc1-deficient cells. Similarly, whereas TGN decreased interleukin-8 (IL-8) levels in culture media of MUC1-expressing A549 cells treated with Pseudomonas aeruginosa strain K (PAK), no differences in IL-8 levels were seen between PAK and PAK plus TGN in MUC1-nonexpressing cells. EMSA confirmed the presence of a PPARγ-binding element in the MUC1 gene promoter. Finally, TGN treatment of A549 cells increased MUC1 promoter activity measured using a MUC1-luciferase reporter gene, augmented MUC1 mRNA levels by quantitative RT-PCR, and enhanced MUC1 protein expression by Western blot analysis. These combined data are consistent with the hypothesis that PPARγ stimulates MUC1/Muc1 expression, thereby blocking PMA/PAK-induced TNF-α/IL-8 production by airway epithelial cells.

Download Full-text

Adrenomedullin Is Both Proinflammatory and Antiinflammatory: Its Effects on Gene Expression and Secretion of Cytokines and Macrophage Migration Inhibitory Factor in NR8383 Macrophage Cell Line

Endocrinology ◽

10.1210/en.2004-1080 ◽

2005 ◽

Vol 146 (3) ◽

pp. 1321-1327 ◽

Cited By ~ 68

Author(s):

Louisa Y. F. Wong ◽

Bernard M. Y. Cheung ◽

Yuk-Yin Li ◽

Fai Tang

Keyword(s):

Inflammatory Response ◽

Migration Inhibitory Factor ◽

Macrophage Migration Inhibitory Factor ◽

Culture Media ◽

Inhibitory Factor ◽

Macrophage Migration ◽

Macrophage Cell ◽

Gene Expressions ◽

Initiation And Propagation ◽

Tnf Α

Adrenomedullin (ADM) is a potent vasorelaxant peptide that plays important roles in cardiovascular homeostasis and inflammatory response. ADM derived from macrophages is one of the major sources of ADM that is produced in the inflammatory process. To assess the functions of ADM in inflammation, we studied the temporal changes in ADM production and its effect on secretion of macrophage migration inhibitory factor (MIF) and cytokine response of NR8383 rat macrophages activated by lipopolysaccharide (LPS). NR8383 cells were stimulated by LPS in the absence and presence of exogenous ADM, and the concentrations of ADM, MIF, and proinflammatory cytokines (IL-6, TNF-α, and IL-1β) in the culture media and gene expressions of the cells were measured. We confirmed that the secretion and mRNA expression of ADM in the macrophages were markedly increased by LPS. ADM increased initial secretion of MIF and IL-1β from both nonstimulated and LPS-stimulated cells, and it also increased basal and LPS-induced IL-6 secretion of the cells by 2- to 15-fold. However, it reduced secretion of TNF-α from LPS-stimulated cells by 34–56%. Our results suggest that ADM modulates MIF secretion and cytokine production and plays important roles in both the initiation and propagation of the inflammatory response.

Download Full-text

Epigenetic targeting of the ACE2 and NRP1 viral receptors limits SARS-CoV-2 infectivity

Clinical Epigenetics ◽

10.1186/s13148-021-01168-5 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Maria Laura Saiz ◽

Marta L. De Diego ◽

Darío López-García ◽

Viviana Corte-Iglesias ◽

Aroa Baragaño Raneros ◽

...

Keyword(s):

Inflammatory Response ◽

Cell Lines ◽

Hdac Inhibitors ◽

Potential Candidate ◽

Dependent Manner ◽

Messenger Rnas ◽

N Protein ◽

Protein Levels ◽

Viral Spread ◽

Tnf Α

Abstract Background SARS-CoV-2 uses the angiotensin-converting enzyme 2 (ACE2) and neuropilin-1 (NRP1) receptors for entry into cells, and the serine protease TMPRSS2 for S protein priming. Inhibition of protease activity or the engagement with ACE2 and NRP1 receptors has been shown to be an effective strategy for blocking infectivity and viral spreading. Valproic acid (VPA; 2-propylpentanoic acid) is an epigenetic drug approved for clinical use. It produces potent antiviral and anti-inflammatory effects through its function as a histone deacetylase (HDAC) inhibitor. Here, we propose VPA as a potential candidate to tackle COVID-19, in which rapid viral spread and replication, and hyperinflammation are crucial elements. Results We used diverse cell lines (HK-2, Huh-7, HUVEC, Caco-2, and BEAS-2B) to analyze the effect of VPA and other HDAC inhibitors on the expression of the ACE-2 and NRP-1 receptors and their ability to inhibit infectivity, viral production, and the inflammatory response. Treatment with VPA significantly reduced expression of the ACE2 and NRP1 host proteins in all cell lines through a mechanism mediated by its HDAC inhibitory activity. The effect is maintained after SARS-CoV-2 infection. Consequently, the treatment of cells with VPA before infection impairs production of SARS-CoV-2 infectious viruses, but not that of other ACE2- and NRP1-independent viruses (VSV and HCoV-229E). Moreover, the addition of VPA 1 h post-infection with SARS-CoV-2 reduces the production of infectious viruses in a dose-dependent manner without significantly modifying the genomic and subgenomic messenger RNAs (gRNA and sg mRNAs) or protein levels of N protein. The production of inflammatory cytokines (TNF-α and IL-6) induced by TNF-α and SARS-CoV-2 infection is diminished in the presence of VPA. Conclusions Our data showed that VPA blocks three essential processes determining the severity of COVID-19. It downregulates the expression of ACE2 and NRP1, reducing the infectivity of SARS-CoV-2; it decreases viral yields, probably because it affects virus budding or virions stability; and it dampens the triggered inflammatory response. Thus, administering VPA could be considered a safe treatment for COVID-19 patients until vaccines have been rolled out across the world.

Download Full-text

Suppression of Murine Endotoxin Response by E5531, a Novel Synthetic Lipid A Antagonist

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.11.2824 ◽

1998 ◽

Vol 42 (11) ◽

pp. 2824-2829 ◽

Cited By ~ 22

Author(s):

Seiichi Kobayashi ◽

Tsutomu Kawata ◽

Akifumi Kimura ◽

Kaname Miyamoto ◽

Koichi Katayama ◽

...

Keyword(s):

Inflammatory Response ◽

Lipid A ◽

Cell Surface Receptor ◽

Dependent Manner ◽

Necrosis Factor Alpha ◽

In Vivo Models ◽

Lps Challenge ◽

Tnf Α

ABSTRACT As a consequence of blood-borne bacterial sepsis, endotoxin or lipopolysaccharide (LPS) from the cell walls of gram-negative bacteria can trigger an acute inflammatory response, leading to a series of pathological events and often resulting in death. To block this inflammatory response to endotoxin, a novel lipid A analogue, E5531, was designed and synthesized as an LPS antagonist, and its biological properties were examined in vitro and in vivo. In murine peritoneal macrophages, E5531 inhibited the release of tumor necrosis factor alpha (TNF-α) by Escherichia coli LPS with a 50% inhibitory concentration (IC50) of 2.2 nM, while E5531 elicited no significant increases in TNF-α on its own. In support of a mechanism consistent with antagonism of binding to a cell surface receptor for LPS, E5531 inhibited equilibrium binding of radioiodinated LPS ([125I]2-(r-azidosalicylamido)-1, 3′-dithiopropionate-LPS) to mouse macrophages with an IC50 of 0.50 μM. E5531 inhibited LPS-induced increases in TNF-α in vivo when it was coinjected with LPS into C57BL/6 mice primed with Mycobacterium bovis bacillus Calmette-Guérin (BCG). In this model, the efficacy of E5531 was inversely correlated to the LPS challenge dose, consistent with a competitive antagonist-like mechanism of action. Blockade of the inflammatory response by E5531 could further be demonstrated in other in vivo models: E5531 protected BCG-primed mice from LPS-induced lethality in a dose-dependent manner and suppressed LPS-induced hepatic injury in Propionibacterium acnes-primed or galactosamine-sensitized mice. These results argue that the novel synthetic lipid A analogue E5531 can antagonize the action of LPS in in vitro and suppress the pathological effects of LPS in vivo in mice.

Download Full-text

Effect of tagitinin C isolated from kembang bulan [ Tithonia diversifolia (Hemsley) A. Gray] leaves on VEGF and TNF- α expressions of keloid fibroblast

Journal of thee Medical Sciences (Berkala Ilmu Kedokteran) ◽

10.19106/jmedsci005204202001 ◽

2020 ◽

Vol 52 (4) ◽

Author(s):

Arif Yusuf Wicaksana ◽

Dwi Aris Agung Nugrahaningsih ◽

Mae Sri Hartati Wahyuningsih

Keyword(s):

Culture Media ◽

Control Group ◽

P Value ◽

Dependent Manner ◽

Collagen Deposition ◽

Tithonia Diversifolia ◽

Active Constituent ◽

Keloid Fibroblast ◽

Tnf Α ◽

Keloid Fibroblasts

Tagitinin C, an active constituent of Tithonia diversifolia (Hemsley) A. Gray, has been proven caninhibit the collagen deposition of keloid fibroblasts in vitro. However, its mechanism of action has not been widely studied. One possible mechanism involves growth factors and cytokines. Vascular endothelial growth factor (VEGF) and tumor necrosis factor alpha (TNF-α) play an important role in the collagen deposition. The study aimed to evaluate the effect of tagitinin C on VEGF and TNF-α expression in keloid fibroblasts culture. An experimental laboratory study using fibroblast cell lines at passages III and IV was performed. Treatments were divided into two groups i.e. the treatment groups after incubation with tagitinin Cat various concentration of 1, 0.5, 0.25, and 0.125μg/ mL for 72 h, and the control group using culture media without tagitinin C. Following after incubation, the VEGF and TNF-α levels of keloid fibroblast culture supernatant were measured by ELISA. Kruskal-Wallis test continued using Mann-Whitney test or one way Anova continued by independent t test were applied to evaluate the differences between groups. A p value of less than 0.05 was considered statistically significant. The VEGF levels significantly decreases in concentration-dependent manner after treatment of the tagitinin C at various concentrations (p<0.05). However, no significantly difference in TNF-α levels was observed (p> 0.05). In conclusion, tagitinin C decreases the VEGF expression of keloid fibroblasts. However, it has no effect on the TNF-α expression.

Download Full-text

Vibrio alginolyticus Triggers Inflammatory Response in Mouse Peritoneal Macrophages via Activation of NLRP3 Inflammasome

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.769777 ◽

2021 ◽

Vol 11 ◽

Author(s):

Jinxin Wang ◽

Qun Ding ◽

Qiankun Yang ◽

Hui Fan ◽

Guili Yu ◽

...

Keyword(s):

Inflammatory Response ◽

Nlrp3 Inflammasome ◽

Peritoneal Macrophages ◽

Vibrio Alginolyticus ◽

Inflammasome Activation ◽

Dependent Manner ◽

Caspase 1 ◽

Tnf Α ◽

Mouse Peritoneal Macrophages

Vibrio alginolyticus is a food-borne marine Vibrio that causes gastroenteritis, otitis media, otitis externa, and septicemia in humans. The pathogenic mechanisms of V. alginolyticus have previously been studied in aquaculture animals; however, the underlying mechanisms in mammals remain unknown. In this study, an in vitro model of mouse peritoneal macrophages infected with V. alginolyticus was established. qPCR results revealed that V. alginolyticus induced the transcription levels of various cytokines, including IL-1β, IL-12, IL-18, TNF-α, IL-17, IL-6, IFN-γ, and IL-10, and the secretion level of IL-1β is the most significant. Inhibition assays with Ac-YVAD-CHO (a caspase-1 inhibitor) and Z-VAD-FMK (a pan-caspase inhibitor) were conducted to determine whether caspase-1 or caspase-11 is involved in V. alginolyticus-triggered IL-1β secretion. Results showed that IL-1β secretion was partly inhibited by Ac-YVAD-CHO and absolutely blocked by Z-VAD-FMK. To explore the sensed pattern recognition receptors, several NLR family members and the AIM2 receptor were detected and many receptors were upregulated especially NLRP3. Moreover, the NLRP3 protein displayed a puncta-like surrounding cell nucleus, which signified that the NLRP3 inflammasome was activated in response to V. alginolyticus infection. Inhibition assays with glyburide and CA-074 methyl ester (K+ outflow inhibitor and cathepsin B inhibitor) blocked IL-1β secretion, which demonstrated the essential role of the NLRP3 inflammasome in inflammatory response. To better understand how V. alginolyticus affects IL-1β release, the NLRP3 inflammasome was detected with doses ranging from 0.1 to 10 MOIs and time periods ranging from 3 to 12 h. Results showed that V. alginolyticus-mediated NLRP3 inflammasome activation was in a time- and dose-dependent manner and IL-1β release peaked at MOI of 1 for 12 h. Most importantly, blocking the NLRP3 inflammasome with inhibitors and the use of NLRP3-/- and caspase-1/11-/- mice could attenuate pro-inflammatory cytokine secretion, such as IL-1β, IL-6, IL-12, and TNF-α. Taken together, our study first found that the NLRP3 inflammasome plays vital roles in V. alginolyticus triggered inflammatory response in mouse peritoneal macrophages. This may provide reference information for the development of potential anti-inflammatory treatments against V. alginolyticus infection.

Download Full-text

Mir-142-3p Regulates Inflammatory Response by Contributing to Increased TNF-α in Chronic Rhinosinusitis With Nasal Polyposis

Ear Nose & Throat Journal ◽

10.1177/0145561319847972 ◽

2019 ◽

Vol 100 (1) ◽

pp. NP50-NP56 ◽

Cited By ~ 5

Author(s):

Xiang Qing ◽

Yongquan Zhang ◽

Ya Peng ◽

Guangxiang He ◽

An Liu ◽

...

Keyword(s):

Inflammatory Response ◽

Chronic Rhinosinusitis ◽

Messenger Rna ◽

Nasal Polyposis ◽

Inflammatory Factors ◽

Dependent Manner ◽

Expression Levels ◽

Qrt Pcr ◽

Human Nasal Epithelial Cells ◽

Tnf Α

Objective: Previous studies suggested that microRNAs played an important role in the progression of inflammation and remodeling of chronic rhinosinusitis with nasal polyposis. However, the abnormal expression of microRNAs and regulation cytokine expression in nasal polyposis are not clear. Method: The miR-142-3p and tumor necrosis factor α (TNF-α) expression levels in chronic rhinosinusitis with nasal polyposis were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The miR-142-3p and TNF-α levels in human nasal epithelial cells (HNEpC) after stimulation by lipopolysaccharide (LPS) were detected by qRT-PCR. Moreover, HNEpCs were transfected by miR-142-3p mimics or inhibitor or cotransfected with si-TNF-α to evaluate the regulation of miR-142-3p on TNF-α which affects the production of inflammatory factors. Results: The miR-142-3p and TNF-α were significantly higher in nasal mucosa of chronic rhinosinusitis with polyps patients compared to normal human. MiR-142-3p and TNF-α expression levels were increased after LPS stimulation in a dose- and time-dependent manner. Knockdown of miR-142-3p in HNEpCs downregulated TNF-α expression at both messenger RNA and protein levels. Conclusions: It is indicated that miR-142-3p may participate in the regulation of the body’s inflammatory response through the LPS-TLR-TNF-α signaling pathway in chronic rhinosinusitis with nasal polyposis.

Download Full-text

Inhibition of Complement and CD14 Attenuates the Escherichia coli-Induced Inflammatory Response in Porcine Whole Blood

Infection and Immunity ◽

10.1128/iai.01305-08 ◽

2008 ◽

Vol 77 (2) ◽

pp. 725-732 ◽

Cited By ~ 24

Author(s):

Ebbe Billmann Thorgersen ◽

Anne Pharo ◽

Karin Haverson ◽

Anne K. Axelsen ◽

Peter Gaustad ◽

...

Keyword(s):

Escherichia Coli ◽

Inflammatory Response ◽

Proinflammatory Cytokines ◽

Whole Blood ◽

Innate Immune ◽

Dependent Manner ◽

Bacterial Clearance ◽

E Coli ◽

Tnf Α ◽

Dose Dependent

ABSTRACT The innate immune response is a double-edged sword in systemic inflammation and sepsis. Uncontrolled or inappropriate activation can damage and be lethal to the host. Several studies have investigated inhibition of downstream mediators, including tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β). Emerging evidence indicates that upstream inhibition is a better therapeutic approach for attenuating damaging immune activation. Therefore, we investigated inhibition of two central innate immune pathways, those of complement and CD14/Toll-like receptor 4 (TLR4)/myeloid differentiation protein 2 (MD-2), in a porcine in vitro model of Escherichia coli-induced inflammation. Porcine whole blood anticoagulated with lepuridin, which did not interfere with the complement system, was incubated with E. coli lipopolysaccharide (LPS) or whole bacteria. Inhibitors of complement and CD14 and thus the LPS CD14/TLR4/MD-2 receptor complex were tested to investigate the effect on the inflammatory response. A broad range of inflammatory readouts were used to monitor the effect. Anti-CD14 was found to saturate the CD14 molecule on granulocytes and completely inhibited LPS-induced proinflammatory cytokines in a dose-dependent manner. Anti-CD14 significantly reduced the levels of the E. coli-induced proinflammatory cytokines TNF-α and IL-1β, but not IL-8, in a dose-dependent manner. No effect on bacterial clearance was seen. Vaccinia complement control protein and smallpox inhibitor of complement enzymes, two Orthopoxvirus-encoded complement inhibitors, completely inhibited complement activation. Furthermore, these agents almost completely inhibited the expression of wCD11R3, which is associated with CD18 as a β2 integrin, on porcine granulocytes and decreased IL-8 levels significantly in a dose-dependent manner. As expected, complement inhibition reduced bacterial clearance. We conclude that inhibition of complement and CD14 attenuates E. coli-induced inflammation and might be used as a therapeutic regimen in gram-negative sepsis along with appropriate treatment with antibiotics.

Download Full-text

Immunosuppressive effect of the Fusarium secondary metabolite butenolide in human colon epithelial cells

10.1101/2020.04.16.044388 ◽

2020 ◽

Cited By ~ 1

Author(s):

Lydia Woelflingseder ◽

Gerhard Adam ◽

Doris Marko

Keyword(s):

Inflammatory Response ◽

Secondary Metabolite ◽

Human Colon ◽

Dependent Manner ◽

Fungal Metabolites ◽

Food Contaminants ◽

Trichothecene Mycotoxin ◽

Mechanism Of Inhibition ◽

Tnf Α ◽

Dose Dependent

ABSTRACTButenolide (BUT, 4-acetamido-4-hydroxy-2-butenoic acid gamma-lactone) is a secondary metabolite produced by several Fusarium species and is co-produced with the major trichothecene mycotoxin deoxynivalenol (DON) on cereal grains throughout the world. BUT has low acute toxicity and only very limited occurrence and exposure data are available. The intestinal epithelium represents the first physiological barrier against food contaminants. We aimed to elucidate the intestinal inflammatory response of the human, non-cancer epithelial HCEC-1CT cells to BUT and to characterize potential combinatory interactions with co-occurring trichothecenes, such as DON and NX-3. Using a reporter gene approach, BUT (≥5 μM, 20 h) was found to decrease lipopolysaccharide (LPS; 10 ng/mL) induced nuclear factor kappa B (NF-κB) activation in a dose-dependent manner, and in combinatory treatments represses trichothecene-induced enhancement of this important inflammatory pathway. Analyzing transcription and secretion levels of NF-κB-dependent, pro-inflammatory cytokines, revealed a significant down-regulation of IL-1β, IL-6 and TNF-α in IL-1β-stimulated (25 ng/mL) HCEC-1CT cells after BUT exposure (10 μM). Trichothecene-induced expression of pro-in-flammatory cytokines by the presence of 1 μM DON or NX-3 was substantially suppressed in the presence of 10 μM BUT. The emerging mycotoxin BUT has the ability to suppress NF-κB-induced intestinal inflammatory response mechanisms and to modulate substantially the immune responsiveness of HCEC-1CT cells after trichothecene treatment. Our results suggest that BUT, present in naturally occurring mixtures of Fusarium fungal metabolites, should be increasingly monitored, and the mechanism of inhibition of NF-κB that might affect the pathogenesis or progression of intestinal inflammatory disorders, should be further investigated.

Download Full-text

Induction of Apoptosis by Paramyxovirus Simian Virus 5 Lacking a Small Hydrophobic Gene

Journal of Virology ◽

10.1128/jvi.77.6.3371-3383.2003 ◽

2003 ◽

Vol 77 (6) ◽

pp. 3371-3383 ◽

Cited By ~ 57

Author(s):

Yuan Lin ◽

Angela C. Bright ◽

Terri A. Rothermel ◽

Biao He

Keyword(s):

Neutralizing Antibodies ◽

Culture Media ◽

Simian Virus ◽

Hendra Virus ◽

Dependent Manner ◽

Simian Virus 5 ◽

Tnf Α ◽

Animal Pathogens ◽

Infected Cells ◽

Small Hydrophobic

ABSTRACT Simian virus 5 (SV5) is a member of the paramyxovirus family, which includes emerging viruses such as Hendra virus and Nipah virus as well as many important human and animal pathogens that have been known for years. SV5 encodes eight known viral proteins, including a small hydrophobic integral membrane protein (SH) of 44 amino acids. SV5 without the SH gene (rSV5ΔSH) is viable, and growth of rSV5ΔSH in tissue culture cells and viral protein and mRNA production in rSV5ΔSH-infected cells are indistinguishable from those of the wild-type SV5 virus. However, rSV5ΔSH causes increased cytopathic effect (CPE) and apoptosis in MDBK cells and is attenuated in vivo, suggesting the SH protein plays an important role in SV5 pathogenesis. How rSV5ΔSH induces apoptosis in infected cells has been examined in this report. Tumor necrosis factor alpha (TNF-α), a proinflammatory cytokine, was detected in culture media of rSV5ΔSH-infected cells. Apoptosis induced by rSV5ΔSH was inhibited by neutralizing antibodies against TNF-α and TNF-α receptor 1 (TNF-R1), suggesting that TNF-α played an essential role in rSV5ΔSH-induced apoptosis in a TNF-R1-dependent manner. Examination of important proteins in the TNF-α signaling pathway showed that p65, a major NF-κB subunit whose activation can lead to transcription of TNF-α, was first translocated to the nucleus and was capable of binding to DNA and then was targeted for degradation in rSV5ΔSH-infected cells while expression levels of TNF-R1 remained relatively constant. Thus, rSV5ΔSH induced cell death by activating TNF-α expression, possibly through activation of the NF-κB subunit p65 and then targeting p65 for degradation, leading to apoptosis.

Download Full-text