Thymosin-beta4 inhibits corneal epithelial cell apoptosis after ethanol exposure in vitro

PURPOSE

The purpose of this study was to determine the effect of thymosin beta 4 (Tbeta(4)) treatment on human corneal epithelial cells exposed to ethanol in vitro. The efficacy of Tbeta(4) in preventing mitochondrial disruption and in inhibiting caspase-mediated apoptosis was examined.

METHODS

Nontransformed human corneal epithelial cells (HCECs) at passage 4 were untreated or treated with ethanol (20% for 20 seconds) or a combination of ethanol and Tbeta(4). The cells were allowed to recover from ethanol treatment for 24 hours. Mitochondrial membrane integrity and the release of cytochrome c to the cytoplasm were assessed using microscopy, Western blot, and ELISA. Bcl-2 expression and cell proliferation were measured using ELISA. Colorimetric activity assays were completed for caspase-2, -3, -8, and -9.

RESULTS

Tbeta(4) treatment decreased deleterious mitochondrial alterations, significantly decreased cytochrome c release from mitochondria, and increased Bcl-2 expression in ethanol-exposed human corneal epithelial cells. In ethanol-exposed corneal epithelium Tbeta(4) treatment inhibited caspase-2, -3, -8, and -9 activity, with caspase-8 showing the most significant inhibition. Tbeta(4) treatment resulted in no significant effect on the proliferation of human corneal epithelial cells after ethanol exposure.

CONCLUSIONS

Tbeta(4) plays an antiapoptotic role under conditions of epithelial cell challenge with an external stress such as exposure to ethanol. Tbeta(4) may function as an antiapoptotic agent by inhibiting the release of cytochrome c from mitochondria and by suppressing the activation of caspases.

The modulation of thymosin alpha 1 in the maturation, differentiation and function of murine bone marrow-derived dendritic cells in the absence or presence of tumor necrosis factor-alpha

Thymosin alpha 1 (Talpha1) has immunomodulatory effects on T-cells, NK-cells and macrophages, but its action on dendritic cells (DCs), which are recognized as the sole professional antigen presenting cells (APCs) capable of priming naïve T-cells, is poorly understood. In this study, the effect of Talpha1 in vitro on murine bone marrow-derived DCs (BMDCs) maturation, differentiation, and function with or without tumor necrosis factor-alpha (TNF-alpha), which is one of the important inflammatory parameters, has been investigated. We have shown, through flow cytometry, ELISA and mixed leukocyte reaction (MLR), that Talpha1 promoted CD4-expressed DC differentiation and the expression of activation markers, but did not influence IL-12 production and T cell-stimulatory capacity of DCs in the absence of TNFalpha during BMDCs maturation. Furthermore, in the presence of TNF-alpha, Talpha1 has been shown not only to promote the expression of CD4 on MHC class II+ DCs and enhance the up-regulated levels of mature markers induced by TNF-alpha, but also to suppress the up-regulated IL-12 production. Particularly, thus effects seen were obvious at pharmacological Talpha1 concentrations. However, Talpha1 did not inhibit TNF-alpha-induced T-cell stimulating function of DCs. This is the first reported example of a direct Talpha1-DC interaction and suggests a mechanism by which Talpha1 may in part affect T-cell responses by acting at the DC level and it may play an important role in the modulation of the local inflammatory responses in vivo.

Thymosin β4 induces the synthesis of plasminogen activator inhibitor 1 in cultured endothelial cells and increases its extracellular expression

Thymosin β4(Tβ4), a 4.9-kDa polypeptide primarily known as a main G-actin–sequestering peptide, is present in high concentrations in various cells and in the circulation. We have found that Tβ4 upregulates the expression of plasminogen activator inhibitor 1 (PAI-1) in endothelial cells measured both at the level of mRNA and protein synthesis. This effect seems to be cell specific and was not observed when other cells such as human fibroblasts, PC3, and U937 were tested. Tβ4 significantly activated the PAI-1 promoter in EA.hy 926 cells transiently transfected either with plasmid p800LUC containing PAI-1 promoter fragment (–800 to +71) or the PAI-1 promoter linked with green fluorescent protein. Tβ4 mediated up-regulation of PAI-1 involved activation of the mitogen-activated protein kinase cascade. Furthermore, Tβ4 enhanced c-Fos/c-Jun DNA-binding activity to the activator protein 1 (AP-1)–like element (–59 to –52). The specificity of this binding activity was demonstrated by competition electrophoretic mobility shift assay and after transfection of EA.hy 926 cells with the mutated PAI-1 promoter. Taken together, these data indicate that, in response to Tβ4 stimulation, AP-1 activity increases to enhance PAI-1 transcription through its unique AP-1–like element at –59 to –52 in the PAI-1 promoter.

Thymosin beta 4 stimulates laminin-5 production independent of TGF-beta

Thymosin beta 4 (Tbeta(4)) stimulates epithelial cell migration and promotes laminin-5 (LM-5) expression. Using gene expression analysis with human corneal epithelial cells treated with Tbeta(4), we find that both LM-5 gamma2 chain and transforming growth factor beta 1 (TGFbeta-1) are increased by more than 2-fold over untreated cells. These findings were confirmed by RT-PCR and at the protein level. Although TGFbeta-1 increases LM-5 synthesis in a dose-dependent manner, it does not appear to be the mechanism by which Tbeta(4) acts on LM-5 gamma2 chain synthesis based on three independent experiments. In a time-course analysis, Tbeta(4) increases LM-5 gamma2 chain expression at 2 h and peaks at 6 h, while TGFbeta-1 increases LM-5 gamma2 chain expression only at 4 h and peaks at 8 h. When Tbeta(4)-induced LM-5 gamma2 chain expression is blocked with neutralizing antibodies to TGFbeta-1, LM-5 gamma2 chain expression is increased. Finally, in TGFbeta-1 knock-out mice, Tbeta(4) increases LM-5 gamma2 chain expression to levels higher than that observed in wild-type mice treated with Tbeta(4). These findings demonstrate that Tbeta(4) induces both TGFbeta-1 and LM-5 gamma2 chain expression in corneal epithelial cells. Tbeta(4) and TGFbeta-1 increase LM-5 gamma2 chain expression by independent pathways. Suppression of TGFbeta-1 further increases LM-5 gamma2 chain expression.

Thymosin-alpha 1 plus interferon-alpha for naive patients with chronic hepatitis C: results of a randomized controlled pilot trial

In this pilot study, we evaluated the efficacy of interferon-alpha (IFN) plus Thymosin-alpha 1 (TA1) to that of IFN alone in naive patients with chronic hepatitis C. Twenty-two patients were randomized to receive interferon-alpha 2b (3 million units three times a week) plus thymosin-alpha l (900 microg/m2 body surface area) and 19 received interferon-alpha 2b alone at the same dose. Patients were treated for 6 months and followed up for another 6 months. Biochemical (alanine aminotransferase values) and virological (hepatitis C virus-RNA) responses to treatment were determined. Combination treatment showed significantly higher efficacy than monotherapy in achieving virological end-of-treatment response (P = 0.03). At 6-month follow up, the sustained biochemical and virological response was not different between the two groups. Our results indicate that the immune modulator TA1 may enhance the end-of-treatment response in naive patients with chronic hepatitis C. Higher doses and/ore more prolonged courses as well as the association with new interferon formulation such as pegylated interferons could improve the sustained response rates to this treatment.

Thymosin beta4 increases hair growth by activation of hair follicle stem cells

Thymosin beta4, a 43-amino acid polypeptide that is an important mediator of cell migration and differentiation, also promotes angiogenesis and wound healing. Here, we report that thymosin beta4 stimulates hair growth in normal rats and mice. A specific subset of hair follicular keratinocytes in mouse skin expresses thymosin beta4 in a highly coordinated manner during the hair growth cycle. These keratinocytes originate in the hair follicle bulge region, a niche for skin stem cells. Rat vibrissa follicle clonogenic keratinocytes, closely related, if not identical, to the bulge-residing stem cells, were isolated and their migration and differentiation increased in the presence of nanomolar concentrations of thymosin beta4. Expression and secretion of the extracellular matrix-degrading enzyme matrix metalloproteinase-2 were increased by thymosin beta4. Thus, thymosin beta4 accelerates hair growth, in part, due to its effect on critical events in the active phase of the hair follicle cycle, including promoting the migration of stem cells and their immediate progeny to the base of the follicle, differentiation, and extracellular matrix remodeling.

Thymosin alpha-1 modulates excitatory synaptic transmission in cultured hippocampal neurons in rats

Thymosin alpha-1 (Talpha1) not only possesses immunoregulatory properties in periphery but also is expressed in the central nervous system (CNS) and affects the function of the CNS. To further elucidate the role of Talpha1 in the CNS, the whole-cell recording technique was used to observe the effect of Talpha1 on the spontaneous excitatory synaptic transmission in cultured rat hippocampal neurons. The results showed that acute treatment with Talpha1 significantly enhanced the frequency of AMPA-mediated spontaneous excitatory postsynaptic current (sEPSC) at the concentrations of 1 and 10 microg/ml and also enhanced the frequency of AMPA-mediated miniature excitatory postsynaptic current (mEPSC) at 10 microg/ml. However, the amplitude of both sEPSC and mEPSC were not changed by Talpha1. Those results suggested that Talpha1 involves in the regulation of excitatory synaptic transmission in hippocampal neurons, which contribute to its neurophysiological function in the CNS.

The actin binding site on thymosin beta4 promotes angiogenesis

Thymosin beta4 is a ubiquitous 43 amino acid, 5 kDa polypeptide that is an important mediator of cell proliferation, migration, and differentiation. It is the most abundant member of the beta-thymosin family in mammalian tissue and is regarded as the main G-actin sequestering peptide. Thymosin beta4 is angiogenic and can promote endothelial cell migration and adhesion, tubule formation, aortic ring sprouting, and angiogenesis. It also accelerates wound healing and reduces inflammation when applied in dermal wound-healing assays. Using naturally occurring thymosin beta4, proteolytic fragments, and synthetic peptides, we find that a seven amino acid actin binding motif of thymosin beta4 is essential for its angiogenic activity. Migration assays with human umbilical vein endothelial cells and vessel sprouting assays using chick aortic arches show that thymosin beta4 and the actin-binding motif of the peptide display near-identical activity at ~50 nM, whereas peptides lacking any portion of the actin motif were inactive. Furthermore, adhesion to thymosin beta4 was blocked by this seven amino acid peptide demonstrating it as the major thymosin beta4 cell binding site on the molecule. The adhesion and sprouting activity of thymosin beta4 was inhibited with the addition of 5-50 nM soluble actin. These results demonstrate that the actin binding motif of thymosin beta4 is an essential site for its angiogenic activity.

Thymosin beta(4) reduces lethality and down-regulates inflammatory mediators in endotoxin-induced septic shock

Thymosin beta(4) (Tbeta(4)), a highly conserved peptide with immunomodulatory properties, is the major actin-sequestering peptide in mammalian cells. Recent studies have established that Tbeta(4) can accelerate wound healing in full thickness skin wounds and following burn injuries to the cornea. In the eye studies, the accelerated healing due to Tbeta(4) was accompanied by a significant reduction in polymorphonuclear leukocyte (PMN) infiltration and a several-fold decrease in interleukin-1beta (p< or =0.015) and 6-keto-prostaglandin F(1alpha) (6-keto-PGF1alpha, p< or =0.05). Given the recognized role of proinflammatory cytokines in septic shock and of extracellular F- and G-actin in the pathophysiology of multiple organ dysfunction, we have investigated the role of Tbeta(4) in sepsis. We report that an LD(50) dose of LPS (24 mg/kg) in rats resulted in a significant reduction of Tbeta(4) levels in the blood. Furthermore, administration of 100 microg of Tbeta(4) immediately following and at 2 and 4 h after an LD(50) dose of LPS (60 mg/kg) in mice significantly reduced mortality rates (p< or =0.024) and lowered blood levels of a number of inflammatory cytokines, eicosanoids, and other molecules that are highly elevated following endotoxin administration. In studies in human subjects given low doses of endotoxin (4 ng/kg LPS) and in patients with septic shock, we have also observed significant decreases in blood levels of Tbeta(4). The rapid disappearance of Tbeta(4) in the blood following LPS administration or during septic shock suggests that Tbeta(4) may be involved in early events leading to activation of the inflammatory cascade and ultimately the clinical sequelae of sepsis. The results of this study indicate that Tbeta(4) may have utility in the clinic in the treatment of septic shock and in syndromes associated with actin toxicities.

[Effect of thymosin alpha 1 on cellular immune function in elderly patients with malignant tumor]

OBJECTIVE

To investigate the effect of thymosin alpha 1 on cellular immune function in the elderly patients with malignant tumor.

METHODS

Thirty patients with malignant tumor were injected with thymosin alpha 1 subcutaneously at the dose of 1.6 mg q.d. for the first month and q.o.d. for the following month. The number of T cell subgroups and the activity of NK cell in peripheral blood were detected and the quality of life of the patients were evaluated before treatment and at the end of treatment.

RESULT

Treatment of thymosin alpha 1 increased the number of CD4 cells and improved the NK activity, and also improved the quality of life of the elderly patients with malignant tumor. There were no side effects found.

CONCLUSION

Thymosin alpha 1 can enhance the cellular immune function of the elderly patients with malignant tumor.

Effect of thymosin-alpha1 on the production of nitric oxide by tumor-associated macrophages

The present investigation was conducted to study the effect of thymic peptide: thymosinalpha1 (thyalpha1) on the activation of tumor associated mphi (TAM) obtained from mice bearing a transplantable T cell lymphoma of spontaneous origin designated as Dalton's lymphoma, to produce nitric oxide (NO). It was found that in vivo administration of aqueous thymic extract obtained from thymus of normal mice or thyalpha1 could activate the TAM to produce enhanced amount of NO which was further augmented on in vivo treatment of these TAM by LPS. These observations suggest that thyalpha1 could prime TAM for activation by second signal of LPS. The study also presents evidence that tumor cell elaborate factors that enhance the effect of thyalpha1 on TAM for production of NO. This is the first study to show that thyalpha1 can activate TAM directly even in the absence of LPS, and may, therefore, have clinical significance.

Distinctive roles of PHAP proteins and prothymosin-alpha in a death regulatory pathway

A small molecule, alpha-(trichloromethyl)-4-pyridineethanol (PETCM), was identified by high-throughput screening as an activator of caspase-3 in extracts of a panel of cancer cells. PETCM was used in combination with biochemical fractionation to identify a pathway that regulates mitochondria-initiated caspase activation. This pathway consists of tumor suppressor putative HLA-DR-associated proteins (PHAP) and oncoprotein prothymosin-alpha (ProT). PHAP proteins promoted caspase-9 activation after apoptosome formation, whereas ProT negatively regulated caspase-9 activation by inhibiting apoptosome formation. PETCM relieved ProT inhibition and allowed apoptosome formation at a physiological concentration of deoxyadenosine triphosphate. Elimination of ProT expression by RNA interference sensitized cells to ultraviolet irradiation-induced apoptosis and negated the requirement of PETCM for caspase activation. Thus, this chemical-biological combinatory approach has revealed the regulatory roles of oncoprotein ProT and tumor suppressor PHAP in apoptosis.

[Hematopoietic inhibitors elaborated by bone marrow endothelial cells]

In this study, the roles of hematopoietic inhibitors elaborated by bone marrow endothelial cells in the proliferation and differentiation of hematopoietic progenitors were investigated. Murine bone marrow endothelial cell conditioned medium (BMEC-CM) was collected and the components with > 10 kD and < 10 kD were obtained by centrifugal ultrafiltration. The effect of BMEC-CM and its components on proliferation of hematopoietic progenitors was evaluated by CFU-GM and HPP-CFC assay and antibody neutralization test. The expression of the inhibitors in BMEC and BMEC-CM was detected by RT-PCR and Western blot, and change of proliferation and differentiation-related genes during expansion of hematopoietic progenitors was examined by membrane hybridization technique.

THE RESULTS

(1) When BME C-CM and its components directly were added to CFU-GM and HPP-CFC culture system, BMEC-CM had no effect on colony formation, > 10 kD component enhanced and < 10 kD component inhibited the formation of CFU-GM and HPP-CFC. (2) When BMEC-C M and its components were added to liquid culture system of marrow cells, after 24 hours incubation, CFU-GM decreased and HPP-CFC increased significantly in B MEC-CM group, CFU-GM increased and HPP-CFC had no significant change in > 10 kD component group; and both CFU-GM and HPP-CFC reduced in < 10 kD group. (3) MIP-2, MIP-1 alpha, MSP, TGF-beta, TNF-alpha, IFN-gamma and T beta 4 were expressed in murine marrow endothelial cells, and MIP-2, MIP-1 alpha, MSP, TGF-beta, TNF-alpha and T beta 4 were existed in BMEC-CM. (4) Antibody neutralization test results demonstrated that TGF-beta, MSP, MIP-1 alpha, IFN-gamma and T beta 4 existed in BMEC-CM had significant suppressive effects on CFU-GM and HPP-CFC. (5) T beta 4 combined with 5 hematopoietic cytokines (SCF, IL-3, IL-6, GM-CSF and EPO) added to CD34(+) cells expansion culture system, HPP-CFC significantly increased compared with 5 cytokines group. T beta 4 could downregulated the expression of proliferation and differentiation-related genes and signal transduction-related genes. It is concluded that BM EC-CM promotes the proliferation of early hematopoietic progenitor cells, and this effect is related with the inhibitors existed in BMEC-CM and it could be executed via influencing cell proliferation and differentiation-related genes and signal-related genes.

Cloning expression in E.coli and biological activity of human thymosin beta(4)

The cDNA thymosin beta(4) was synthesized by combining of chemical and enzymatic methods. First, two complement fragments of thymosin beta(4) cDNA were synthesized by DNA synthesizer, and then denatured, annealed and extended by DNA polymerase. This fragment of thymosin beta(4) was then inserted into the EcoRV and HindIII restriction endonuclease site of an expression plasmid pLDH4 (a kind of E.coli plasmid) by blunt and cohesive ligations. Finally, the recombinant plasmid which expressed thymosin beta(4) was screened by digestion and DNA sequencing. This recombinant plasmid highly expressed the thymosin beta(4), which accounted for 30% of total bacteria proteins. By salting out and chromatography, a 95% purity of recombinant thymosin beta(4) was obtained. Biological assay indicated that the recombinant thymosin beta(4) could induce lymphocyte proliferation and differentiation.

[Effect of recombinant prothymosin alpha on secretion of IFN-gamma, IFN-alpha and TNF-alpha in vitro]

AIM

To study the effect of prothymosin alpha (Pro T alpha) as a fusion protein on secretion of IFN-gamma, IFN-alpha and TNF-alpha in vitro.

METHODS

The in vitro study was carried out on the culture of splenocytes, splenic and peritoneal macrophages isolated from Balb/c mice. Splenocytes were incubated with various concentrations of Pro T alpha (1 x 10(-7)-1 x 10(-10) mol.L-1) with or without Con A (5 micrograms.mL-1) for 72 h. Splenic and peritoneal macrophages were respectively treated with Pro T alpha (1 x 10(-7)-1 x 10(-10) mol.L-1) in the presence of LPS (10 micrograms.mL-1) for 24 h. Then IFN-gamma, IFN-alpha and TNF-alpha levels in the supernatant were detected by ELISA.

RESULTS

Pro T alpha (1 x 10(-7) mol.L-1) was found to obviously increase IFN-gamma level (P < 0.05) in the supernatant of splenocytes compared with the control group. Moreover, Pro T alpha (1 x 10(-7) mol.L-1) significantly induced the secretion of IFN-alpha (P < 0.01) and TNF-alpha (P < 0.01) in splenic and peritoneal macrophages.

CONCLUSION

In vitro, Pro T alpha could increase the secretion of IFN-gamma, IFN-alpha and TNF-alpha.

Thymosin alpha1. SciClone Pharmaceuticals

Thymosin alpha1 (Talpha1), a synthetic 28-amino acid peptide with multiple biological activities primarily directed towards immune response enhancement, was originally developed by Alpha 1 Biomedicals for the treatment of hepatitis B virus (HBV) infection. SciClone developed and launched Talpha1, under the trade name Zadaxin, for the treatment of HBV and hepatitis C virus (HCV) infections. The drug is also being developed for the treatment of non-small cell lung cancer (NSCLC), hepatocellular carcinoma, AIDS and malignant melanoma. Talpha1 is able to potentiate the action of cytokines and also reduce the hematological toxicity of cytotoxic drug therapy (cyclophosphamide-, 5-fluorouracil-, dacarbazine- or ifosfamide-based regimens). These studies also demonstrated the mechanism of action of Talpha1 and its role as an immune system enhancer. By July 2001, it was in phase III trials in the US in combination with PEGylated interferon-alpha, and later the same month it was approved in the Philippines. SciClone received expanded approval for HBV and HCV infection in Mexico in July 2001. Talpha1 has been launched in Argentina, China, Peru, the Philippines and Singapore for the treatment of chronic HBV infection. The product subsequently received expanded approval for the treatment of both HBV and HCV infection in Argentina. Marketing approval was granted in India for HBV infection in February 2001. The company was working to expand this approval to include HCV infection. In March 2000, approval for treatment of HBV infection was granted in Thailand, Laos and Malta. Approval was also granted in Sri Lanka and Brunei in August 1999. In September 2000, SciClone announced that approval had been expanded to include the treatment of HCV infection as well as the previously approved HBV indication in both Peru and Sri Lanka. In January 1999, SciClone received approval for Talpha1 in Venezuela for the treatment of HBV and HCV infection. The company also filed a marketing application in New Zealand for Talpha1 to treat HBV infection. The drug was approved in South Korea in April 2000, as an influenza vaccine adjuvant and this was expected to be expanded to indude use for treatment of both HBV and HCV infections. In July 2001, it was approved in In September and October 2000, SciClone was granted patents in Mexico and Canada, respectively, for the use of Talpha1 for the treatment of HCV infection. In June 2000, SciClone was issued a Notice of Allowance by the US Patent and Trademark Office for use of Talpha1 in the treatment of HBV infection. The EPO granted a patent, exclusively licensed to SciClone, for the use of Talpha1 as a monotherapy or in combination with interferon, to treat for HCV infection. In April 2001, SciClone received a Notice of Allowance for a US patent covering newly described analogs of Talpha1. The patent gave the Philippines as an adjuvant to chemotherapy for the treatment of various cancers. In December 2001, Talpha1 entered a phase 1 trial program in Europe, with patient enrolment planned for 2002. SciClone exclusive composition-of-matter rights to several families of Talpha1 analogs that could have proprietary therapeutic or biologic distinctions from Talpha1. The company was issued US patents covering the use of Talpha1 for the treatment of HCV infection in August 1998 and the treatment of HBV infection in September 1999. A Notice of Allowance for a second US patent covering the use of Talpha1 was issued in October 1999. In April 1999, SciClone received allowance of a patent from the EPO covering the use of Talpha1 in small cell and non-small cell lung cancer. In August 2001, SciClone received a notice of allowance for patent protection in Japan covering the use of Talpha1. The patent, which extends until 2012, also covers the use of Talpha1 in combination with interferon-alpha for the treatment of HCV infection. SciClone was previously granted a Japanese patent for the use of Talpha1 in the treatment of HBV infection.

Thymosin alpha1 inhibits mammary carcinogenesis in Fisher rats

The effects of thymosin alpha1 (Talpha1) on mammary carcinogenesis was investigated in Fisher rats. Mammary carcinomas were observed 3 months after N-nitrosomethylurea (NMU) injection (10mg, i.p.) into Fisher rats. Daily administration of Talpha1 (10 microg, s.c.) reduced mammary carcinoma incidence and prolonged survival time. Animals treated with exogenous Talpha1 had a significantly greater blood white cell density than control Fisher rats. These results suggest that Talpha1 prevents mammary carcinoma incidence as a result of stimulation of the immune system.

Thymosin beta4 promotes human conjunctival epithelial cell migration

PURPOSE

In this study the effects of thymosin beta4 (Tbeta4) on migration and production of laminin-5 in the human conjunctival cell line HC0597 was analyzed.

METHODS

Boyden chamber assays assessed the ability of Tbeta4 to stimulate in vitro cell migration. Control or Tbeta4-treated cells were processed for immunofluorescence microscopy using antibodies to vinculin or laminin-5. Cell lysates were processed for Western blot and densitometric analysis using antibodies to laminin-5 alpha3 or gamma2 chains.

RESULTS

Tbeta4 stimulated migration in a dose-dependent manner. Focal adhesions present in Tbeta4-treated cells were smaller and more rounded compared to the "streaks" characteristic of controls. Western blot analysis and densitometry revealed that Tbeta4-treated cells expressed more laminin-5 alpha3 and gamma2 chain protein.

CONCLUSION

Tbeta4 stimulates in vitro conjunctival epithelial cell migration, and results in altered focal adhesion formation and increased extracellular laminin-5 deposition. The increased migration may be correlated with increased production of laminin-5.

Biochemical and morphogenic effects of the interaction between protein kinase C-epsilon and actin in vitro and in cultured NIH3T3 cells

Protein kinase C-epsilon coordinately regulates changes in cell growth and shape. Cells overproducing protein kinase C-epsilon spontaneously acquire a polarized morphology and extend long cellular membrane protrusions that are reminiscent of the morphology observed in ras-transformed fibroblasts. Here we report that the regulatory C1 domain contains an actin binding hexapeptide motif that is essential for the morphogenic effects of protein kinase C-epsilon in cultured NIH3T3 murine fibroblasts. The extension of elongate processes by protein kinase C-epsilon transformed fibroblasts appeared to be driven by a kinase-independent mechanism that required organized networks of both actin and microtubules. Flow cytometry of phalloidin-stained cells demonstrated that protein kinase C-epsilon significantly increased the cellular content of polymerized actin in NIH3T3 cells. Studies with a cell-free system suggest that protein kinase C-epsilon inhibits the in vitro disassembly of actin filaments, is capable of desequestering actin monomers from physiologically relevant concentrations of thymosin beta4, and increases the rate of actin filament elongation by decreasing the critical concentration of actin. Based on these and other observations, it is proposed that protein kinase C-epsilon may function as a terminal downstream effector in at least one of the signaling pathways that mitogens engage to initiate outgrowth of cellular protrusions.

Thymosin alpha1 accelerates restoration of T cell-mediated neutralizing antibody response in immunocompromised hosts

Thymosin alpha1 is a biological response modifier that has been used clinically for the treatment of chronic hepatitis B viral infection. Both immunomodulatory and immediate intracellular mechanisms have been postulated to explain the effect of thymosin alpha1 on hepatocytes infected with hepatitis B virus (HBV). Here, we established a new animal model and the related suitable conditions to access the thymosin activity by means of measuring the production of neutralizing antibody against hepatitis B surface antigen (HBsAg). We proved that chemically synthesized thymosin alpha1 restored the T cell-mediated antibody production following its suppression in mice by 5-fluorouracil (5-FU), and found that thymosin alpha1 showed activity at a low dose of 30 microg/kg. Further studies utilizing the flowcytometric analysis showed that thymosin alpha1 at this dose accelerated the replenishment and maturation of thymocytes while the expression of Smoothened (Smo) of the Hedgehog (Hh)-signaling in CD4-CD8- thymocytes, the potent negative regulator of proliferative responses, was not affected. The restoration of some of the defects in the host defense systems may facilitate elimination of infectious agents, and the present study provides a novel model to define the restoration of T cell-mediated immune responses to hepatitis B virus in vivo.

Involvement of mitogen-activated protein kinases in the signal transduction pathway of bone marrow-derived macrophage activation in response to in vitro treatment with thymosin alpha 1

Thymosin alpha 1 (Talpha1), a 28-amino acid, acidic thymic peptide, is a promising natural biological response modifier (BRM), which augments and regulates the immune network and is thought to be immunostimulatory also. Recently, we have reported the ability of Talpha1 to activate macrophages to tumoricidal state. In the present investigation, the activation of the p42/44 MAP kinase (MAPK)/c-Jun NH2 terminal kinase (JNK) pathway in response to in vitro treatment with Talpha1 in murine bone marrow-derived macrophages (BMDMs) has been demonstrated. The activation and expression of phospho-p42/44 MAPK was dose as well as time dependent with maximum expression occurring at 5-15 min following stimulation with 100 ng/ml of Talpha1. The expression of phospho-p42/44 MAPK was inhibited by the MAPK inhibitor, PD98059, pertussis toxin (PTX), tyrosine kinase inhibitor-genistein and P13K inhibitor-wortmannin. Talpha1-induced BMDM tumoricidal functions like the production of NO and TNF-alpha, the key mediator molecules of macrophage cytotoxicity, were also inhibited by the MAPK inhibitor, PD98059, in a dose-dependent manner. These observations suggest that p42/44 MAPK activation is one of the essential signaling events triggered by Talpha1 and may be responsible for the in vitro activation of BMDMs.

Effect of thymosin peptides on the chick chorioallantoic membrane angiogenesis model

The effect of alpha- and beta-thymosin peptides, namely prothymosin alpha (ProT(alpha)), thymosin alpha(1) (T(alpha)1), parathymosin alpha (ParaT(alpha)), thymosin beta(4) (Tbeta4), thymosin beta(10) (Tbeta10), and thymosin beta(9) (Tbeta9), on the angiogenesis process was investigated using the chick chorioallantoic membrane as an in vivo angiogenesis model. The thymosin peptides tested were applied in 10 microl aliquots containing 0.01-4 nmoles of Tbeta4, Tbeta10 or Tbeta9, 0.016-6.66 nmoles of T(alpha)1, 4.1 pmoles-1.66 nmoles of ProT(alpha), and 4.4 pmoles-1.76 nmoles of ParaT(alpha). Phorbol 12-myristate 13-acetate and hydrocortisone were also used as positive and negative control, respectively. Tbeta4, ProT(alpha) and T(alpha)1 were found to enhance angiogenesis, while Tbeta10, Tbeta9 and ParaT(alpha) exhibited an inhibitory effect on the angiogenesis process. When mixtures of Tbeta4 and Tbeta10 containing active amounts of the two peptides at different proportions were applied, the promoting effect of Tbeta4 on angiogenesis was reversed in the presence of increasing concentrations of Tbeta10 and vice versa. The effect of Tbeta10, Tbeta9, ProT(alpha) and ParaT(alpha), in parallel with Tbeta4 and T(alpha)1, on the angiogenesis process was investigated for the first time as far as we know and the results of this study offer more insight into the biological regulatory roles of thymosin peptides, and provide helpful information about their therapeutic potential. Whether these agents could be used either as inhibitors of angiogenesis in disease states where uncontrolled angiogenesis is involved, e.g. in carcinogenesis, or as angiogenesis promoters that could be useful in wound healing, fracture repair, peptic ulcers etc., remains to be further studied.

Thymosin alpha-1

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of thymosin alpha-1 (TA1) are reviewed. TA1 is a synthetic polypeptide. The drug is in Phase III trials for the treatment of hepatitis C and in Phase II trials for hepatitis B. Additional possible indications are malignant melanoma, hepatocellular carcinoma, drug-resistant tuberculosis, and DiGeorge's syndrome. TA1 is thought to modulate the immune system by augmenting T-cell function. TA1 may affect thymocytes by stimulating their differentiation or by converting them to active T cells. TA1 is rapidly absorbed, achieving peak serum concentrations within two hours. Blood levels return to baseline within 24 hours, and the serum half-life is approximately 2 hours. TA1's efficacy in hepatitis B has been evaluated in 195 patients in four clinical trials. One study found hepatitis B virus (HBV) DNA clearance at six months in 9 of 17 patients receiving TA1, compared with 10 of 16 patients treated with interferon alfa-2b (IFN-alpha 2b) and 4 of 15 historical controls. An open-label trial found HBV DNA clearance in 53% of patients at six months. A randomized, controlled trial found HBV DNA clearance in 40.6% and 25.6% of patients treated with TA1 for 6 and 12 months, respectively, compared with 9.4% of untreated controls. Efficacy for hepatitis C has been evaluated in 162 patients in three clinical trials. In one trial, the number of patients who achieved normal serum alanine aminotransferase (ALT) levels did not differ significantly between TA1 and placebo. In the other two trials, combination TA1 and IFN-alpha 2b was compared with IFN-alpha 2b alone. One trial found a normal serum ALT level at six months in 71% of patients receiving combination therapy, versus 35% of patients receiving IFN-alpha 2b alone. Hepatitis C virus RNA clearance occurred in 65% of patients treated with combination therapy and 29% of patients treated with IFN-alpha 2b alone. The third trial, comparing combination TA1 and IFN-alpha 2b with IFN-alpha 2b alone and with placebo, found normalization of ALT levels at six months in 37.1% of patients receiving combination therapy, 16.2% of patients receiving IFN-alpha 2b alone, and 2.7% of patients receiving placebo. TA1 is well tolerated. Most studies observed only local irritation at the injection site. For hepatitis B and C, TA1 1.6 mg (900 micrograms/m2) should be administered subcutaneously twice a week. Clinical trials of TA1 for chronic hepatitis B or C have had mixed results. TA1 may be useful as monotherapy for hepatitis B or in combination with IFN-alpha 2b for hepatitis C, but its effects on morbidity and mortality remain to be seen.