Thyroid hormones and cathepsin D activity in the rat liver, kidney and brain

Postpartum Heart Failure Complicated With Thyroiditis: A Concealed Aggravator of Peripartum Cardiomyopathy?

The etiology of peripartum cardiomyopathy (PPCM) remains unestablished, but the involvement of abnormal autoimmunity has been suggested. We report a case of PPCM that was triggered by postpartum thyroiditis. Despite the presence of myocardial damage indicated by cardiac magnetic resonance imaging, the patient's cardiac function completely recovered with the addition of bromocriptine to standard therapies. We discuss the role of thyroid hormones in the development of PPCM through aggravation of a prolactin-dependent antiangiogenic effect, and we argue that more attention should be paid to postpartum thyroiditis as a novel risk factor for PPCM.

Immunoexpressions of embryonic and nonembryonic stem cell markers (Nanog, Thy-1, c-kit) and cellular connections (connexin 43 and occludin) on testicular tissue in thyrotoxicosis rat model

In this study, possible thyrotoxicosis-related histological changes in testicular tissues of rats with experimentally induced thyrotoxicosis model were evaluated on cellular connections and stem cell markers. Two experimental groups, thyrotoxicosis and control, each consisting of eight animals were used. Rats in the thyrotoxicosis group were injected intraperitoneally with 3,3',5-triiodo-l-thyronine (50 µg/100 g body weight/day) for 10 days. At the end of the study, animals in both groups were anesthetized, and blood samples were collected for biochemical analyses. Their testes were dissected out and histological procedure was conducted to perform further histochemical, immunohistochemical analyses and tissue expression analysis by real-time polymerase chain reaction. Expression of the stem cell markers such as c-kit and Thy-1 significantly decreased in the testes of the thyrotoxicosis group compared with the control group; however, Nanog expression was not detected in any of the groups. Similarly, connexin 43 and occludin expressions were also found to be significantly lower in the thyrotoxicosis group. These results on cellular connections are supported with the tissue expression analysis. Our findings are indicative of supporting microenvironmental tissue decay rather than parenchyma damage, which has been actually ignored in the literature. In conclusion, experimental thyrotoxicosis model may have adverse effects on the cell junctional complexes, cell-cell interactions, and pluripotency capacity.

Effect of antimalarials treatment on rat liver lysosomal function-Anin vivo study

Effects of treatmentin vivo with the antimalarials:chloroquine (CQ), primaquine (PQ) and quinine(Q) on lysosomal enzymes and lysosomal membrane integrity were examined. Treatment with the three antimalarials showed an apparent increase in the membrane stability. CQ treatment resulted in increase in both the 'free' and 'total' activities of all the enzymes i.e. acid phosphatase, RNase II, DNase II and cathepsin D. PQ treatment lowered the 'free' and 'total' activities of acid phosphatase and cathepsin D, but the DNase II activities increased. Treatment with Q resulted in increased 'free' and 'total' activities of RNase II and DNase II. While 'free' activities of acid phosphatase and cathepsin D were low; the 'total' activities increased significantly. Our results suggest that a generalized increase in free nucleases activities following prolonged treatment with antimalarials may lead to cell damage and/or necrosis.

Propylthiouracil reduces xenograft tumor growth in an athymic nude mouse prostate cancer model

METHODS

Several anecdotal reports indicate that cancer may occasionally remain in a dormant state for prolonged periods in patients with hypothyroidism. Once the hypothyroid state is recognized and supplementation therapy with thyroid hormones is initiated, disease progression occurs. In this experiment, 6-n-propyl-2-thiouracil (PTU) was added to the water of athymic nude mice. The animals were subsequently inoculated with cells from a human prostate cancer cell line.

RESULTS

The growth rate of subcutaneously implanted prostate xenografts was significantly slower in mice treated with PTU compared with mice that did not receive PTU. In a separate experiment, tritiated thymidine incorporation assays were performed in DU145 and PC3 human prostate cancer cells with and without PTU. No significant differences were observed, indicating that PTU did not exert any antitumor effect in vitro.

CONCLUSIONS

Our study demonstrates that PTU inhibits the growth of human prostate tumors in nude mice via an indirect effect. This antitumor effect may be caused by hypothyroidism. This is the first in vivo study suggesting potential therapeutic applications for thyroid hormone manipulations in human cancer of the prostate. Further studies will determine growth kinetics of xenotransplanted prostate cancer in vitro and in vivo. PTU-induced hypothyroidism may be further explored in conjunction with other antineoplastic therapy.

Natural sex steroids and their xenobiotic analogs in animal production: growth, carcass quality, pharmacokinetics, metabolism, mode of action, residues, methods, and epidemiology

Natural and xenobiotic compounds having sex-related actions have long been used for growth promotion and various changes in carcass quality in meat animals. The first compounds used were synthetic estrogens; however, later on a whole battery of compounds having androgenic, and progestogenic actions have also been involved. In surveying the effects of these compounds in meat-producing animals, it became clear that these drugs increase the growth rate of the treated animals and bring about changes in the carcass that are generally characterized by lower fat content and more lean mass. Extensive studies undertaken in various countries, including the European Economic Community (EEC), have shown that if used according to good husbandry practices, the meat from treated animals does not have excessive amounts of residues compared with the endogenous amount of steroid production in the animals in question and also in human beings. The banning of these compounds in the European community brought a new phenomenon of illegal or black market cocktails. These mixtures of anabolic steroids are injected into the body of the animals rather than implanted in the ears, which is the normal practice in countries where they have not yet been banned. Several screening and confirmatory methods are now available for monitoring programs. However, these programs need excessive resources in terms of manpower, funds, and proper legislation, which in underdeveloped countries is questionable, particularly in the absence of strong scientific evidence for the exercise.

Is activation of lysosomal enzymes responsible for paracetamol-induced hepatotoxicity and nephrotoxicity?

Paracetamol overdose (300 mg kg(-1)) in mice resulted in a time-dependent increase in the liver weight; no change was seen for the kidney. The total acid phosphatase activities in the two tissues increased significantly 0.5 h after paracetamol overdose and remained elevated up to 3 h. Free as well as total cathepsin D activities increased significantly in both the tissues within 2-2.5 h of paracetamol treatment. Simultaneously tyrosine positive materials in the two tissues increased. RNAse II and DNAse II activities were low in liver and kidneys of the controls. Paracetamol treatment elevated both free and total RNAse II activity in the two tissues by 0.5 h. Maximum activity of DNAse II (free and total) was seen at 2.5 h after paracetamol administration. The results suggest that concerted action of cathepsin D, RNAse II and DNAse II may be responsible for paracetamol-induced hepatotoxicity and nephrotoxicity.

Is respiratory activity in the brain mitochondria responsive to thyroid hormone action?: a critical re-evaluation

The effects of in vivo treatment with graded doses (0.5-1.5 micrograms/g body weight) of thyroid hormones, tri-iodothyronine (T3) and thyroxine (T4), for 4 consecutive days to euthyroid rats on the respiratory activity of isolated brain mitochondria were examined. T4 stimulated coupled State-3 respiration with glutamate, pyruvate + malate, ascorbate + tetramethyl-p-phenylenediamine and succinate, in a dose-dependent manner; T3 was effective only at the highest (1.5 micrograms) dose employed. T4 was more effective than T3 in stimulating respiratory activity. State-4 respiratory rates were in general not influenced except in the case of the ascorbate + tetramethyl-p-phenylenediamine system. Primary dehydrogenase activities, i.e. glutamate dehydrogenase, malate dehydrogenase and succinate dehydrogenase, were stimulated about 2-fold; interestingly mitochondrial but not cytosolic malate dehydrogenase activity was influenced under these conditions. The hormone treatments did not greatly influence the mitochondrial cytochrome content. The results therefore suggest that thyroid hormone treatment not only stimulates primary dehydrogenase activities but may also directly influence the process of mitochondrial electron transfer.

Changes induced in astrocyte cathepsin D by cytokines and leupeptin

Cathepsin D is widely, but unevenly, distributed among cells and is capable of degrading a number of neural peptides and proteins. The present study was undertaken to examine the level of cathepsin D in astrocytes that might be relevant to its induction in inflammatory demyelination. Primary astrocytes were cultured from neonatal rat cerebrums according to the method of McCarthy and de Vellis. Based on staining for cell markers, cultures were greater than 95% astrocytes and less than 3% microglia. Under serum-free conditions, leupeptin induced a 1.4- to 2.0-fold increase, maximal by 48 hours, in cathepsin D protein quantified by a radioimmunoassay. Cathepsin D enzymatic activity, inhibitable by pepstatin, also increased. Northern blot analysis demonstrated that leupeptin also increased cathepsin D mRNA expression. Kinetic analysis indicated that maximal cathepsin D mRNA levels are detected 24 h after stimulation with leupeptin. Exposure of astrocytes under the same conditions to rat recombinant interferon-gamma, human recombinant tumor necrosis factor-alpha, human recombinant interleukin-1 beta, lipopolysaccharide, calcium ionophore, or a combination of these reagents did not increase the level of cathepsin D above controls. These results indicate that astrocytic cathepsin D mRNA and protein can be induced by selected materials. Furthermore, the effects attributed to leupeptin as a proteinase inhibitor may be modified by its ability to increase cathepsin D activity.

Immunocytochemical localization of cathepsin D in rat ventral prostate: evidence for castration-induced expression of cathepsin D in basal cells

Cathepsin D (EC3.4.23.5) is an aspartyl endopeptidase involved in lysosomal proteolysis. Its functional role is uncertain. This study was undertaken to determine the cellular and subcellular distribution of cathepsin D in the normal rat ventral prostate and its possible role in the castration-induced atrophy of the gland. Cathepsin D was localized immunohistochemically to perinuclear lysosomes in secretory cells, in capillary endothelial cells, and, occasionally, in stromal cells of the untreated animal. Castration resulted in an increased number of cathepsin D-positive cells in the stroma within 24 hr. By 48 hr after castration autophagolysosomes formed in secretory cells and apoptotic bodies appeared in the epithelium. Although apoptotic bodies generally contained immunoreactive cathepsin D, a subpopulation of larger apoptotic bodies, which commonly rested on the basement membrane and contained multiple inclusions, were more variable in cathepsin D expression. The induction of cathepsin D in dendritic cells basally oriented in the epithelium was noted at 4 days of castration. These cells had a phagocytic phenotype, were distributed periodically along the basement membrane, and were not found in ductal epithelia. Treatment with actinomycin D or hydrocortisone to reduce the rate of regression of the ventral prostate blocked the appearance of these cathepsin D-positive, basally oriented epithelial cells. Our data indicate that this cathepsin D-positive, phagocytic cell differentiates from a cell resident in the prostatic epithelium. We suggest that it differentiates from basal cells in the secretory tubuloalveolar portion of the gland and that it is involved in the destruction of regressed secretory cells.

Insulin-dependent changes in lysosomal cathepsin D activity in rat liver, kidney, brain and heart

Streptozotocin-induced diabetes resulted in a decrease in the cathepsin D activity (free and total) in rat liver, kidney, brain and heart with a concomitant increase in tissue protein content and amino acids pool size. Treatment with insulin brought about the restoration of the cathepsin D activity to normal or greater than normal levels; tissue protein content and amino acids pool size also returned to normal values.

Effect of experimental thyrotoxicosis on oxidative phosphorylation in rat liver, kidney and brain mitochondria

Coupled phosphorylation was examined in liver, kidney and brain mitochondria from rats made thyrotoxic by injecting repeated doses of triiodothyronine. Liver and kidney mitochondria were maximally affected under these conditions, whereas effects on brain mitochondria were marginal. State-3 respiration rates with succinate decreased considerably in all the tissues, whereas glutamate oxidation increased in liver, but decreased in kidney and brain mitochondria. Oxidation rates of beta-hydroxybutyrate decreased in kidney and brain mitochondria but were not significantly affected in liver mitochondria. Oxidation of ascorbate + TMPD was not affected. State-4 respiration rates increased in general with all the substrates resulting in lowering of the RCI. The ADP/O ratios decreased in a site-specific manner in the mitochondria from the three tissues. The content of cytochrome b decreased in all three tissues, whereas the content of cytochrome c + c1 increased in liver and kidney but decreased in brain. The content of cytochrome a, however, was not significantly affected. Basal and Mg2+-stimulated ATPase activities increased in mitochondria of liver and kidney but not in those of brain; total ATPase activities, however, were not altered. The results imply that excessive levels of thyroid hormones over normal in the serum can lead to impairment of mitochondrial energy metabolism in a tissue-specific manner.