thymosin and Hypertension

A variety of cells and cytokines have been shown to be involved in the whole process of hypertension. Data from experimental and clinical studies on hypertension have confirmed the key roles of immune cells and inflammation in the process. Dysfunction of the thymus, which modulates the development and maturation of lymphocytes, has been shown to be associated with the severity of hypertension. Furthermore, gradual atrophy, functional decline or loss of the thymus has been revealed to be associated with aging. The restoration or enhancement of thymus function via upregulation in the expression of thymus transcription factors forkhead box N1 or thymus transplantation may provide an option to halt or reverse the pathological process of hypertension. Therefore, the thymus may be key in hypertension and associated target organ damage, and may provide a novel treatment strategy for the clinical management of patients with hypertension in addition to different commercial drugs. The purpose of this review is to summarize and discuss the advances in our understanding of the impact of thymus function on hypertension from data from animal and human studies, and the potential mechanisms.

Topics: Aging; Animals; Humans; Hypertension; Models, Biological; Thymosin; Thymus Gland

Thymosin β4 (Tβ4), a ubiquitous peptide, regulates several cellular processes that include cell morphology, wound healing, and inflammatory response. Administration of exogenous Tβ4 is protective in diabetic nephropathy and in a unilateral ureteral obstruction model. However, the role of endogenous Tβ4 in health and disease conditions remains unclear. To elucidate the pathophysiological role of endogenous Tβ4 in hypertension, we examined angiotensin-II (Ang-II)-induced renal and cardiac damage in Tβ4 knockout (Tβ4 KO) mice. Tβ4 KO and wild-type C57BL/6 mice were infused continuously for 6 weeks with either vehicle or Ang-II (980 ng/kg per minute). At baseline, Tβ4 deficiency did not affect renal and cardiac function. Systolic blood pressure in the Ang-II group was similar in wild-type and Tβ4 KO mice (wild-type Ang-II, 179.25±10.11 mm Hg; Tβ4 KO Ang-II, 169.81±6.54 mm Hg). Despite the similar systolic blood pressure after Ang-II infusion, Tβ4-deficient mice had dramatically increased albuminuria and decreased nephrin expression in the kidney (

Topics: Acute Kidney Injury; Angiotensin II; Animals; Blood Pressure; Cardiomyopathies; Hypertension; Infusions, Intravenous; Male; Mice; Mice, Knockout; Microfilament Proteins; Random Allocation; Rats; Thymosin

We developed a sensitive, selective and accurate method based on liquid chromatography with tandem mass spectrometry (LC-MS/MS) to determine N-terminal thymosin-β peptides of Ac-SDKP and Ac-ADKP in human plasma samples. Quantification of Ac-SDKP and Ac-ADKP was performed using solid phase extraction (SPE) based on C(18), reversed phase LC separation, and stable isotope dilution electrospray ionization-MS/MS in multiple reaction-monitoring (MRM) mode. The Ac-SDKP-(13)C(6), (15)N(2) and Ac-ADKP-d(7) were synthesized for the internal standards. These MRM monitoring ions were m/z 488→129 (quantitative ion)/226 for Ac-SDKP, m/z 496→137 for Ac-SDKP-(13)C(6), (15)N(2), m/z 472→129 (quantitative ion)/226 for Ac-ADKP, and m/z 479→129 for Ac-ADKP-d(7), respectively. Lower limit of quantitation (LLOQ) of Ac-SDKP and Ac-ADKP was 0.1ng/mL in human plasma. Recovery values were ranged from 94.7% to 106.3% for inter- (RSD: 0.6-3.5%) and intra- (RSD: 0.4-4.9%) day assays. Plasma Ac-SDKP levels were significantly higher in hemodialyzed subjects treated with angiotensin-converting enzyme inhibitors of enalapril (27.3±24.6ng/mL, n=10) and trandolapril (12.3±16.9ng/mL, n=18) than healthy (0.4±0.2ng/mL, n=7) and hemodialyzed subjects (0.6±0.2ng/mL, n=34). This analytical method would be useful to measure N-terminal thymosin-β peptides in human plasma for the clinical study.

Topics: Adult; Angiotensin-Converting Enzyme Inhibitors; Carbon Isotopes; Chromatography, High Pressure Liquid; Deuterium; Drug Monitoring; Female; Humans; Hypertension; Indicator Dilution Techniques; Male; Middle Aged; Nitrogen Isotopes; Oligopeptides; Peptide Fragments; Renal Dialysis; Renal Insufficiency; Solid Phase Extraction; Tandem Mass Spectrometry; Thymosin

We studied the effect of treatment with Thymosin Fraction 5 (Fr-5) on the restoration of T-cell functions and the induction of antitumor immunity in spontaneously hypertensive rats (SHR) with congenital T-cell depression. SHR showed a reduced number of rosette-forming thymocytes early in their lives, and in vitro incubation of SHR thymocytes with Fr-5 restored the numbers of rosette-forming T-cells to the normal level for Wistar/HMK rats, the original strain of SHR. In vivo treatment of SHR with various doses of Fr-5 (0.5, 1.0, or 2.0 mg/kg, 6 times every other day) also increased significantly the blastogenic responses of their spleen cells to phytohemagglutinin but failed to promote plaque-forming cell responses to sheep red blood cells. These immunological restorative effects by Fr-5 were dose dependent. In contrast, treatment with lower doses of Fr-5 (0.25 or 0.50 mg/kg) showed greater curative effects on a high antigenic fibrosarcoma (SMT-6) than did treatment with higher doses of Fr-5 (1.0 or 2.0 mg/kg). This was confirmed by the fact that treatment with a 0.5-mg/kg dose of Fr-5 caused a significant suppressive effect on the growth of a weakly antigenic and highly metastatic adenocarcinoma (SST-2) in SHR with a consequent prolongation of survival days, whereas treatment with a 1.0- or 2.0-mg/kg dose of Fr-5 was without any effect. In order to clarify this mechanism, we studied the effect of pretreatment with cyclophosphamide (CY) on the development of antitumor delayed-type hypersensitivity (DTH) reaction in the SMT-6-bearing SHR treated with Fr-5 (0.5 or 2.0 mg/kg). Treatment with 0.5 mg of Fr-5 per kg significantly increased the DTH reaction to SMT-6 cells in both CY-pretreated and untreated SHR. In contrast, treatment with 2.0 mg of Fr-5 per kg produced a significant antitumor DTH reaction in SHR pretreated with CY but failed to induce the DTH reaction in SHR untreated with CY. These results suggest that higher doses of Fr-5 may induce preferentially suppressor T-cells rather than killer T-cells in tumor-bearing SHR with congenital T-cell depression.

Topics: Animals; Antibody Formation; Cell Differentiation; Cyclophosphamide; Dose-Response Relationship, Drug; Hypersensitivity, Delayed; Hypertension; Leukocyte Count; Lymphocyte Activation; Rats; Rats, Inbred SHR; T-Lymphocytes; Thymosin

Recent evidence of immunologic abnormalities in the spontaneously hypertensive rat (SHR) have been reported as one of the underlying causes in the pathogenesis of hypertension. In this study, monoclonal antibodies were used in a direct immunofluorescence assay to analyze the percentage of lymph node T cell subsets in untreated controls compared to thymosin treated SHR and Wistar Kyoto (W/K) rats. Results indicated that there were 19.7% T helper cells in the lymph nodes of the untreated SHR and 10.8% in the W/K, while the SHR suppressor population was 15.5% and the W/K 24.4%. Administration of thymosin, fraction 5 or the thymosin peptide alpha 7 increased suppressor cell number 2.5 to 3 fold and was successful in lowering blood pressure. Use of the Alzet mini-osmotic pump, containing a 2 week supply of thymosin, fraction 5 or alpha 7, was also effective in lowering blood pressure. In addition, thymosin treatment increased plaque forming cells approximately 2 to 6 fold in both SHR and W/K animals depending on the mode of administration. Female rats were more responsive to treatment with thymosin than male rats.

Topics: Animals; Antibody Formation; Blood Pressure; Female; Hypertension; Male; Rats; Rats, Mutant Strains; T-Lymphocytes; T-Lymphocytes, Helper-Inducer; T-Lymphocytes, Regulatory; Thymosin

Spontaneously hypertensive male and female rats (SHR) were compared with Wistar/Kyoto (W/K) controls at 15 wk and 80 wk of age. Treatment of the young and old hypertensives with thymosin, fraction 5, lowered the blood pressure within 4 wk of the start of treatment. Following 10 wk of injections, the blood pressures of the hypertensive rats remained at a depressed level for about 6 wk. The thymic hormone raised the depressed spontaneous T-cell rosette formation of the aged hypertensive rat and increased the lymph node T-cell response to the mitogens, Con A and PHA. Thymosin administration over a period of 7 wk increased the size of the aged hypertensive thymus. No similar effect was observed in the W/K. Spleen cell production of prostaglandin E (PgE) was markedly higher in the young hypertensive and immune complex deposition was found in the glomeruli and tubules of the aged SHR kidneys. Thymosin lowered the high level of PgE to normal and decreased the immune complex deposition in the kidney. IgG1 levels were considerably depressed in the SHR as compared to the W/K. Following thymosin administration levels of IgG1 increased 2-fold in both rat strains. Plaque-forming cells from the spleens of the untreated SHR were about 3-fold less than those of the age-matched W/K. Following treatment with thymosin the number of plaque-forming cells of both groups demonstrated a substantial further decrease. Spontaneous hypertension in rats is similar, in certain respects to autoimmune-like diseases in humans with a depression in T-cell activity as well as immune complex deposition; both conditions being altered by exposure to a thymic extract.

Topics: Aging; Animals; Antibody-Producing Cells; Blood Pressure; Dose-Response Relationship, Drug; Female; Guinea Pigs; Hemolytic Plaque Technique; Hypertension; Lymphocyte Activation; Male; Prostaglandins E; Rats; Rats, Inbred Strains; Rats, Mutant Strains; Rosette Formation; Thymosin; Thymus Hormones