NaBu Addition Research Articles

All-trans retinoic acid in combination with sodium butyrate enhances specific monoclonal antibody productivity in recombinant CHO cell line.

The effects of all-trans retinoic acid (RA) and sodium butyrate (NaBu) on growth, viability and antibody production of two types of transfected Chinese hamster ovary cell lines (CHO-K1 and CHO-S) were investigated using a batch mode cell culture. By adding 0.5mM NaBu in the CHO-K1 cell culture, the cell specific productivity (Qp) and antibody concentration increased by five- and threefold, respectively. The optimal concentration of RA was 100nM which resulted in twofold increase in antibody production. In a combination model, RA applied at early growth phase of CHO-K1 cells followed by addition of NaBu with lowering culture temperature at the end of stationary phase resulted in two- and threefold increase in Qp and final antibody concentration, respectively. The latter strategy was also applied on suspended CHO-S cells with enhanced Qp and antibody concentration, but to a lesser extent than the CHO-K1 cells. In conclusion, our results demonstrate that the addition of RA and NaBu along with lowering the culture temperature can increase cell culture period as well as Qp and the final concentration of recombinant monoclonal antibody in both CHO-K1 and CHO-S cells without any significant change in binding affinity of the mAb.

Impact of sodium butyrate and mild hypothermia on metabolic and physiological behaviour of CHO TF 70R cells

Background: To reduce costs associated with productivity of recombinant proteins in the biopharmaceutical industry, research has been focused on regulatory principals of growth and survival during the production phases of the cell culture. The main strategies involve the regulation of cell proliferation by the modulation of cell cycle control points (G1/S or G2/M) with mild hypothermia and the addition of sodium butyrate (NaBu). In this study, batch culture strategies were evaluated using CHO TF 70R cells producing the recombinant human tissue plasminogen activator (rh-tPA), to observe their individual and combined effect on the cellular physiological state and relevant kinetic parameters. Results: NaBu addition has a negative effect on the mitochondrial membrane potential (∆Ψm), the values of which are remarkably diminished in cultures exposed to this cytotoxic compound. This effect was not reflected in a loss of cell viability. NaBu and mild hypothermic conditions increased the doubling time in the cell cultures, suggesting that these strategies triggered a general slowing of each cell cycle phase in a different way. Finally, the individual and combined effect of NaBu and mild hypothermia produced an increase in the specific rh-tPA productivity in comparison to the control at 37oC without NaBu. Nevertheless, both strategies did not have a synergistic effect on the specific productivity. Conclusions: The combination of NaBu addition and mild hypothermic condition causes an impact on physiological and metabolic state of CHO TF 70R cells, decreasing cell growth rate and improving glucose consumption efficiency. These results therefore provide a promising strategy to increases specific productivity of rh-tPA. Normal 0 false false false ES-CL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; mso-bidi-font-size:10.0pt; font-family:Arial,sans-serif; color:black; mso-ansi-language:ES-CL; mso-fareast-language:ES-CL;}

Sodium Butyrate Plus EGF and PDGF-BB Aids Cutaneous Wound Healing in Diabetic Mice

Topical application of growth factors is known to aid defective and/or delayed wound healing in diabetic patients. In this study, the effect of topical application of sodium butyrate (Na-Bu), EGF, and PDGF-BB was analysed on the acute cutaneous wound healing in streptozotocin (STZ) induced diabetic mouse model. Two cutaneous wounds were created, one on each of the dorsolateral sides of the diabetic mice. Na-Bu, EGF, and PDGF-BB were applied to the wound either individually or in various combinations. The wound healing was monitored visually and scored as percentage wound closure. The tissue samples were collected from the wound site at 1, 7, and 14 days after wounding from the treated and untreated diabetic wounds and analysed for the levels of EGF-R, β-PDGF-R, HDAC1, p21, and phosphorylated and hypophosphorylated pRb proteins. Our results indicate that application of EGF plus PDGF-BB at the initial stages followed by subsequent addition of Na-Bu along with these growth factors helps wound healing in diabetic mice. It appears that, in addition to cell proliferative agents, a cell differentiation agent, Na-Bu, is necessary for diabetic wound healing. Topical application of EGF plus PDGF-BB along with Na-Bu could be developed as therapeutic agents to treat and manage human diabetic wounds.

Histone deacetylase inhibitors cause TP53-dependent induction of p21/Waf1 in tumor cells with TP53 mutations

The p21/Waf1 protein is one of the main regulators of cell cycle arrest and one of the best-known transcriptional targets of the TP53 protein. Here, we demonstrated that there is activation of expression of the p21/Waf1 gene when the cells were treated with sodium butyrate (NaBu), which is a natural histone deacetylase inhibitor, and investigated whether this phenomenon depends on the presence of a functionally active TP53 protein. For this purpose, we compared the effect of NaBu treatment of human cell lines with different TP53 mutation profiles, including wild-type TP53, single nucleotide substitutions, and the complete absence of the TP53 gene. NaBu activated the TP53 protein via hyperacetylation at the lysine residue K382, without significant changes in the level of protein expression. Western blotting showed that the addition of NaBu triggers a significant increase in the p21/Waf1 protein level in both TP53 wild-type cells and in cells with single nucleotide substitutions in the central DNA-binding core domain (DBD) of the TP53 protein. At the same time, no p21/Waf1 protein induction was observed in cells with complete deletion of the TP53 gene. However, NaBu was not able to induce p21/Waf1 production when the expression of TP53 was transiently knocked down by the p53 siRNA. Overall, our results suggest that NaBu-dependent induction of p21/Waf1 does require the presence of TP53 protein, but, unexpectedly, it can occur regardless of mutational changes in the domain responsible for the TP53 binding to DNA. One possible explanations is that NaBu increases the level of TP53 acetylation and the modified protein is able to establish a new network of protein–protein interactions or trigger conformational changes affecting the TP53-dependent transcriptional machinery even when its DNA binding ability is impaired.

Digital mRNA profiling of N-glycosylation gene expression in recombinant Chinese hamster ovary cells treated with sodium butyrate

To understand the effects of sodium butyrate (NaBu) on protein glycosylation, recombinant Chinese hamster ovary (rCHO) cells producing Fc-fusion glycoprotein were subjected to 3mM NaBu. The addition of NaBu to the cultures reduced the relative proportion of acidic isoforms and sialic acid content of the glycoprotein. Fifty-two N-glycosylation-related gene expressions were also assessed by the NanoString nCounter system, which can provide a direct digital readout using custom-designed color-coded probes. Among them, ten genes (ugp, slc35a2, ganc, man1a, man1c, mgat5a, st3gal5, glb1, neu1, and neu3) were up-regulated and three genes (b4galt2, st3gal3, and neu2) were down-regulated significantly. Altered expression patterns in st3gal3, neu1, and neu3, which have roles in the sialic acid biosynthesis pathway, correlated with reduced sialic acid content of the glycoprotein by NaBu. Taken together, the results obtained in this study provide a better understanding of the detrimental effect of NaBu on N-glycosylation in rCHO cells.

Enhancement of Human Thyrotropin Synthesis by Sodium Butyrate Addition to Serum-Free CHO Cell Culture

The influence of sodium butyrate (NaBu) on the synthesis of recombinant human thyrotropin (r-hTSH) by CHO cells was investigated for the first time. A volumetric productivity of ~10 μg hTSH/mL was repeatedly obtained, with a 3.3-fold increase over a control culture carried out in the absence of NaBu. Since NaBu can induce CHO cell apoptosis and cell growth arrest, the increase in specific productivity was even higher, i.e., ca. 5-fold. Analysis of the N-glycan composition of r-hTSH obtained with the addition of NaBu to the culture medium showed an approximately 12 % increase in the amount of sialic acid, as well as in total carbohydrate, partly due to the increase in the site occupancy from 2.77 to 2.93 glycans per mole of hTSH. The two hormone preparations were characterized by N-glycan structural analysis, which showed that NaBu increased the bi-antennary structures by ca. 13 % while decreasing the tri-antennary structures by approximately the same amount. The in vivo biological activity and pharmacokinetic behavior (clearance) were found to be similar for the two hormone preparations.

Enhancement of adriamycin cytotoxicity by sodium butyrate involves hTERT downmodulation‐mediated apoptosis in human uterine cancer cells

Activation of telomerase is a key element in oncogenesis and resistance to apoptosis for many cancers. Some histone deacetylase inhibitors (HDACi) or chemotheraputic agents have been reported to downregulate the expression of human telomerase reverse transcriptase (hTERT). However, whether hTERT is involved in cell death of uterine cancer cells induced by combination of HDACi with chemotheraputic regents remain unknown. The present study shows that combining sodium butyrate (NaBu) and adriamycin (ADR) inhibits proliferation of uterine cancer cell lines in a concentration and time-dependent manner. Growth inhibition was accompanied by caspase-dependent apoptosis with reduced telomerase activity and decreased hTERT mRNA expression. Ectopic wild type (WT)-hTERT suppressed the apoptosis induced by NaBu/ADR treatment, while knockdown of hTERT sensitized uterine cancer cells to ADR. Moreover, the addition of NaBu significantly enhanced ADR cytotoxicity for the primary uterine cancer cells with high hTERT expression. These data indicate that downregulation of hTERT is an important part of the mechanism by which NaBu enhances ADR-induced apoptosis, and suggests that combining NaBu and ADR may be effective in treating uterine tumor with high telomerase activity.

The combined effect of sodium butyrate and low culture temperature on the production, sialylation, and biological activity of an antibody produced in CHO cells

Cell cultures containing 0 ∼ 5 mM sodium butyrate (NaBu) and grown at 30 and 37°C were conducted to investigate the combined effect of NaBu and low temperature on the quantity and quality of an antibody production in CHO cells. Although NaBu addition decreased cell viability by apoptosis in a dose-dependent manner at both 30 and 37°C, the onset of significant apoptosis induced by NaBu was delayed by lowering culture temperature. The highest specific antibody productivity (qp) of 23.26 pg/cell/day was obtained in the culture containing 2 mM NaBu at 30°C; however, the highest antibody concentration of 167.84 mg/L was achieved in the culture containing 1 mM NaBu at 30°C, as the detrimental effect of further NaBu addition on cell growth compromised its beneficial effect on qp. Moreover, protein quality with respect to the total sialic acid content and Nglycolylneuraminic acid (Neu5Gc) level was evaluated. There were no apparent changes regarding the total sialic acid content of the antibody, but manipulation of cultures with NaBu treatment or (and) low culture temperature did decrease Neu5Gc levels by 5 ∼ 10%. Biological activity of the antibody was also assessed, and no obvious changes were observed. Collectively, the simultaneous application of NaBu and low culture temperature was an effective way to extend culture period and enhance final antibody concentration, without compromising the sialic acid content or biological activity.

Growth factor withdrawal in combination with sodium butyrate addition extends culture longevity and enhances antibody production in CHO cells

The effect of growth factor (GF) and sodium butyrate (NaBu) on Chinese hamster ovary (CHO) cell growth, cell viability and antibody production was investigated using shaking flasks in GF-containing and GF-deficient medium containing 0, 1 and 3mM NaBu. The withdrawal of GF and the addition of NaBu suppressed cell growth, but they significantly increased specific antibody productivity, q(Ab). Interestingly, the withdrawal of GF in combination with the addition of NaBu markedly retarded cell death, leading to extended culture longevity. For instance, at 3mM NaBu, cell viability fell below 80% after day 4 in GF-containing medium, but it remained over 80% until day 18 in GF-deficient medium. Due to the enhanced q(Ab) and the extended culture longevity, approximately 2-fold increase in total antibody production was achieved in pseudo-perfusion culture with 1mM NaBu in GF-deficient medium, compared to the culture in GF-containing medium. The effect of GF and NaBu on the change in the expression and activity of cellular proteins, c-Myc, Bcl-2 and pyruvate dehydrogenase (PDH), was also investigated. Both the withdrawal of GF and the addition of NaBu decreased the expression of c-Myc. The expression of Bcl-2 was enhanced by the addition of NaBu in a dose-dependent manner while it was not affected by the withdrawal of GF. In addition, both the withdrawal of GF and the addition of NaBu reduced metabolic rates, q(Glc), q(Lac) and Y(Lac/Glc), and increased PDH activity while not affecting PDH expression, suggesting that they may reduce the glycolytic rates, but enhance the conversion rates of pyruvate to TCA intermediates. Taken together, the withdrawal of GF in combination with the addition of NaBu can be considered as a relevant strategy for alleviating NaBu-induced cell apoptosis and enhancing antibody production since it can be easily implemented as well as enhance q(Ab) and extend culture longevity.

A DIGE approach for the assessment of differential expression of the CHO proteome under sodium butyrate addition: Effect of Bcl‐xL overexpression

Bcl-x(L), a member of the Bcl-2 family, is known to inhibit apoptosis of recombinant Chinese hamster ovary (rCHO) cells induced by the addition of sodium butyrate (NaBu), which is used for the elevated expression of recombinant protein. In order to understand the intracellular effects of Bcl-x(L) overexpression on CHO cells treated with NaBu, changes to the proteome caused by controlled Bcl-x(L) expression in rCHO cells producing erythropoietin (EPO) in the presence of 3 mM NaBu were evaluated using two-dimensional differential in-gel electrophoresis (2D-DIGE) and MS analysis. The consequences of Bcl-x(L) overexpression were not limited to the apoptotic signaling pathway. Out of eight proteins regulated significantly by Bcl-x(L) overexpression in 3 mM NaBu addition culture, four proteins were related to cell survival (Iq motif-containing GTPase-activating protein 1), cell proliferation (dihydrolipoamide-S-acetyltransferase, guanine nucleotide binding protein alpha interacting 2), and repair of DNA damage (BRCA and CDKN1A interacting protein). Taken together, a DIGE approach reveals that overexpression of Bcl-x(L) not only inhibits apoptosis in the presence of NaBu but also affects cell proliferation and survival in various aspects.

Effect of XIAP overexpression on sodium butyrate-induced apoptosis in recombinant Chinese hamster ovary cells producing erythropoietin

Previously, overexpression of X-linked inhibitor of apoptosis (XIAP), which is known to inhibit activities of caspase-3, -7, and -9 in CHO-K1 cells offered protection against Sindbis virus-induced apoptosis. In this study, the potential role of XIAP overexpression in recombinant CHO (rCHO) cells treated with sodium butyrate (NaBu), which can increase the specific productivity, was investigated by establishing erythropoietin (EPO)-producing rCHO cells with regulated XIAP overexpression (EPO-off-XIAP). The XIAP overexpression in EPO-off-XIAP was tightly regulated by doxycycline. The XIAP overexpression could simultaneously reduce the activation of caspase-3, -7, and -9 induced by NaBu addition. However, XIAP overexpression could not inhibit NaBu-induced apoptosis, as evidenced by DNA fragmentation. In addition, it also did not help the maintenance of the mitochondrial membrane potential in the presence of NaBu, suggesting that the release of mitochondrial proteins might induce caspase-independent apoptosis. As a result, XIAP overexpression did not affect cell growth and EPO production significantly. Taken together, XIAP overexpression, which was reported to inhibit Sindbis virus-induced apoptosis, could not inhibit the NaBu-induced apoptosis in rCHO cells.

Enhanced Human Thrombopoietin Production by Sodium Butyrate Addition to Serum-Free Suspension Culture of Bcl-2-Overexpressing CHO Cells

When sodium butyrate (NaBu) was added to serum-free suspension culture of recombinant CHO (rCHO) cells for enhanced expression of human thrombopoietin (hTPO), apoptotic cell death of rCHO cells was induced in a dose-dependent manner and hTPO quality was deteriorated in regard to sialic acid and acidic isoform contents. To overcome these problems, we overexpressed Bcl-2 protein, an antiapoptotic protein, in rCHO cells producing hTPO. Compared to serum-free suspension culture of control cells without Bcl-2 overexpression (R-neo cells) and NaBu addition, a more than 10-fold increase in the maximum hTPO concentration was obtained in serum-free suspension culture of cells with Bcl-2 overexpression (R-bc12-14 cells) and 3 mM NaBu addition. Both the enhanced specific productivity endowed by NaBu and the extended culture longevity provided by the antiapoptotic effect of Bcl-2 overexpression contributed to the enhancement of maximum hTPO concentration. The problem of quality reduction of hTPO induced by NaBu was not solved by Bcl-2 overexpression, but it was not that significant. Compared to the culture in the absence of NaBu, the percentage of hTPO isoforms in pI 3-5 with high in vivo biological activity produced by R-bc12-14 cells was decreased by approximately 18% in the presence of 3 mM. As a result, a more than 6-fold increase in the production of hTPO isoforms in pI 3-5 was achieved in R-bcl2-14 cell culture with 3 mM NaBu addition. Taken together, the data obtained suggest that Bcl-2 overexpression in rCHO cells and NaBu addition in serum-free suspension culture can be an effective means to enhance the production of highly glycosylated protein such as hTPO.

Effect of N-Acetylcystein on Butyrate-Treated Chinese Hamster Ovary Cells To Improve the Production of Recombinant Human Interferon-β-1a

Sodium butyrate (NaBu) is used as a productivity enhancer for the production of therapeutic recombinant proteins in Chinese hamster ovary (CHO) cells. However, NaBu is well-known for having a cytotoxic effect, thereby inducing apoptosis. As an endeavor to reduce this defect, we studied 11 antioxidants known for inhibiting apoptosis, according to a Plackett-Burman statistical design on CHO cells producing recombinant interferon-beta-1a (IFN-beta). None of the antioxidants that we tested were as effective as N-acetylcystein (NAC) from the point of view of maintaining long-term survival of CHO cells and increasing the production of IFN-beta. In 7.5-L perfusion bioreactor cultures, the addition of NaBu and NAC elongated the culture period to almost 200 h throughout production phase and increased the production yield by 2-fold compared to control cultures containing only NaBu. Glycosylation patterns of produced IFN-beta at each run were also compared in IEF analysis. IEF profiles of where NaBu and NAC were added showed to be more isoforms with a lower pI than those of the control run. The sialic acid content was also increased by 17.7% according to HPLC analysis. Taken together, the data obtained demonstrate that the addition of NAC has positive effects on the elongation of the culture period, improving the production and increasing the sialylation of IFN-beta in NaBu-treated CHO cells.

Enhanced Production of Monomeric Interferon-β by CHO Cells through the Control of Culture Conditions

The enhancement of recombinant protein expression of a transfected cell line is essential for the development of an efficient large-scale bioprocess. The effect of various media additives and temperature conditions were studied in an attempt to optimize protein production, stability, and protein glycosylation from a Chinese hamster ovary (CHO) cell line producing human beta-interferon (Hu-beta-IFN). We observed a decrease in the ELISA response of the glycoprotein in the later stages of batch cultures, which was attributed to molecular aggregation. Cells were subjected to various concentrations of glycerol, dimethyl sulfoxide (DMSO), and sodium butyrate (NaBu) in a variety of culture systems and conditions. The addition of both NaBu and DMSO resulted in higher specific productivities but reduced growth rates that resulted in a net reduction of interferon produced. Glycerol appeared to stabilize the secreted beta-IFN, resulting in reduced aggregation, despite a decrease in cell growth rate. Glycosylation analysis of isolated beta-IFN showed a time-dependent decrease in sialylation in batch culture that was ameliorated by the presence of glycerol. Low-temperature conditions (30 degrees C) had the greatest effect on productivity with a significant increase in beta-IFN titer as well as a reduction in the degree of molecular aggregation.

Influence of co-down-regulation of caspase-3 and caspase-7 by siRNAs on sodium butyrate-induced apoptotic cell death of Chinese hamster ovary cells producing thrombopoietin

Previously, the expression of caspase-3 siRNA could not effectively inhibit sodium butyrate (NaBu)-induced apoptotic cell death of recombinant Chinese hamster ovary (rCHO) cells producing human thrombopoietin (hTPO). Caspase-3 siRNA expressing cells appeared to compensate for the lack of caspase-3 by increasing active caspase-7 levels. For the successful inhibition of NaBu-induced apoptosis of rCHO cells, both caspase-3 and caspase-7 were down-regulated using the siRNA expression vector system. Co-down-regulation of caspase-3 and caspase-7 increased cell viability and extended culture longevity in serum-free culture in the presence or absence of 1 mM NaBu addition. In the cultures with 1 mM NaBu addition, the maximum hTPO concentration in rCHO cells with down-regulation of both caspases was approximately 55% higher than that in rCHO cells without down-regulation of caspases and approximately 16% higher than rCHO cells with down-regulation of only caspase-3. However, in the culture with 3 mM NaBu, this strategy could not dramatically enhance the culture longevity and hTPO production, compared to Bcl-2 overexpression. The different result in hTPO production between down-regulation of caspases and Bcl-2 overexpression may be because the down-regulation of caspase-3 and caspase-7, unlike Bcl-2 overexpression, could not maintain mitochondrial membrane potential in the presence of 3 mM NaBu. Taken together, co-down-regulation of caspase-3 and caspase-7 is effective in regard to extension of culture longevity and enhancement of hTPO production in a serum-free culture in the presence or absence of 1 mM NaBu addition.

The histone deacetylase inhibitor sodium butyrate inhibits baculovirus-mediated transgene expression in Sf9 cells

Recent studies have indicated that histone deacetylase inhibitors (HDACis) could enhance and prolong expression of exogenous genes delivered by various viral vehicles in mammalian cells, including baculovirus vectors. In this study, the effects of HDACis on expression of a baculovirus-mediated eGFP reporter gene under control of baculovirus late promoter p10 in Sf9 cells were evaluated. It was found that sodium butyrate (NaBu) decreased the expression level of the target gene driven by p10 promoter by four to fivefold. Moreover, addition of NaBu increased DNaseI-sensitivity of transgene p10 promoter region and did not influence viral DNA replication. FACS assay has shown that both NaBu and fluorodeoxyuridine (FdUrd) blocked Sf9 cells at G1 phase and inhibited the target gene expression. Another HDACi, trichostatin, had little effects on both cell cycle and Ac-p10-eGFP expression, strongly suggesting that cell cycle arrest accounts for the mechanisms by which NaBu inhibits Ac-p10-eGFP expression. The inhibiting effects of NaBu on baculovirus transgene expression in Sf9 cells are promoter specific since the enhancement of NaBu on transgene expression in insect and mammalian cells are mediated by baculovirus harboring a murine cytomegalovirus (mCMV) immediate early promoter. This study was aimed at improving the productivity of the recombinant proteins and providing a better understanding of the epigenetic regulation of baculovirus gene expression.

Influence of down-regulation of caspase-3 by siRNAs on sodium-butyrate-induced apoptotic cell death of Chinese hamster ovary cells producing thrombopoietin

Sodium butyrate (NaBu) can enhance the expression of foreign protein of recombinant Chinese hamster ovary (rCHO) cells, but it can also inhibit cell growth and induce cellular apoptosis. Thus, the beneficial effect of using a higher concentration of NaBu on foreign protein expression in rCHO cells is compromised by its growth inhibitory and cytotoxic effects. To overcome this cytotoxic effect of NaBu, an expression vector of small interfering RNAs (siRNAs) targeting against caspase-3, a key effector component in apoptosis, was constructed and transfected into rCHO cells producing human thrombopoietin (hTPO). Using this siRNA strategy, rCHO cells (F21 cells) expressing a low level of caspase-3 proenzyme determined by RT-PCR and Western blot analysis were established. Under the condition of 1–5 mM NaBu addition at the exponential growth phase, down-regulation of caspase-3 in F21 cells could not effectively inhibit NaBu-induced apoptotic cell death. This NaBu-induced apoptotic cell death occurred because F21 cells appeared to compensate for the lack of caspase-3 by increasing the active caspase-7 level. These results suggest that the intracellular caspase's interconnectivity should be taken into consideration for the successful inhibition of apoptosis of rCHO cells.

Synergy Between Deacetylase Inhibitors and IL-1β in Activation of the Serum Amyloid A2 Gene Promoter

Butyrate (NaBu) regulates intestinal inflammatory gene expression in part through inhibition of deacetylase activity, but the exact mechanisms involved remain to be determined. In this study, we showed by Northern blot a synergistic induction of the acute phase protein gene SAA2 with a combination of deacetylase inhibitors (Trichostatin A or NaBu) and IL-1beta in the colon carcinoma cell line Caco-2. While the NF-kappa B DNA-binding site was essential for SAA2 regulation by IL-1beta and deacetylase inhibitors, the C/EBP DNA-binding site modulated SAA2 expression levels, as assessed by transient transfection assays and mutagenesis studies. NaBu was sufficient to induce SAA2 expression after transient treatment with IL-1beta and, conversely, IL-1beta induced SAA2 after transient treatment with NaBu. These data suggest that pretreatment with either NaBu or IL-1beta predisposes the SAA2 promoter to further stimulation. Indeed, both NaBu and IL-1beta led to increased recruitment of NF-kappa B p65, C/EBPbeta, and C/EBP delta, and decreased NF-kappa B p50 and C/EBP alpha DNA-binding to the proximal SAA2 promoter, as assessed by chromatin immunoprecipitation assays. Interestingly, while IL-1beta, in contrast to NaBu, induced histone H4 acetylation, addition of IL-1beta and NaBu increased histone H4 acetylation and both C/EBPbeta and NF-kappa B p65 DNA-binding. Therefore, these results suggest that NaBu and IL- 1beta mediate SAA2 synergistic induction by establishing and maintaining similar and complementary chromatin modifications and transcription factor recruitment as well. In addition to global effects, NaBu specifically regulate gene expression, as exemplified by SAA2.

Effect of simultaneous application of stressful culture conditions on specific productivity and heterogeneity of erythropoietin in Chinese hamster ovary cells.

A single stressful culture condition induced by hypoosmotic stress (210 mOsm kg(-1)), low culture temperature (32 degrees C), or NaBu addition (1 mM) resulted in a 1.8- to 2.2-fold enhancement of specific erythropoietin (EPO) productivity (qEPO) of recombinant Chinese hamster ovary (rCHO) cells compared to normal culture condition (37 degrees C and 310 mOsm kg(-1)). Simultaneous application of these stressful conditions further enhanced qEPO up to approximately 5-fold. However, the quality of EPO was affected by stressful culture conditions. The proportion of acidic isoforms of EPO under a single stressful condition was 2.8-13.8% lower than that under normal culture condition. Simultaneous application of the stressful conditions further decreased the portion of acidic isoforms but not significantly. Despite 5-fold enhancement of q(EPO), the portion of acidic isoforms under the simultaneous application of stressful culture conditions was 12.9-21.6% lower than that under normal culture condition. Taken together, these results suggest the potential of simultaneous application of different stressful culture conditions to the production phase of two-stage culture, where cell growth and production phases are separated, for improved EPO production.

Effect of sodium butyrate on the production, heterogeneity and biological activity of human thrombopoietin by recombinant Chinese hamster ovary cells

Human thrombopoietin (hTPO) is a heavily glycosylated protein with 6 and 24 potential N- and O-glycosylation sites, respectively. To determine the effect of sodium butyrate (NaBu) on the production and quality of hTPO in recombinant Chinese hamster ovary (rCHO) cells, NaBu (0–10 mM) was added to the cultures of exponentially growing cells. NaBu addition significantly increased both the specific and volumetric hTPO production, although it decreased the cell viability by apoptosis in a dose-dependent manner. The highest hTPO concentration of 82.2 ± 5.6 μg ml −1 was obtained in the culture with 3 mM NaBu addition. Compared with the culture without NaBu addition, the culture with 3 mM NaBu resulted in a 6.4-fold increase in q TPO and a 3.3-fold increase in the final hTPO concentration on day 7. However, NaBu deteriorated the quality of hTPO, resulting from increased heterogeneity, reduced acidic hTPO isoforms, reduced α(2 → 3) sialylation, and decreased in vivo biological activity. We also found that the biological activity of hTPO in the culture with 3 mM NaBu addition collected on day 7 was 72% of that in the culture without NaBu addition. Taken together, the use of NaBu or its optimal concentration for high-level expression of a heavily glycosylated protein like hTPO should be determined by considering its detrimental effect on the quality of glycoprotein.