Publications

Suicide inactivation of hepatic cytochrome P450 (P450) enzymes 2C11, 2C6, and 3A1/A2 by 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine (DDEP) in intact rats results in prosthetic heme destruction, albeit by apparently distinct mechanisms. Such heme destruction is now shown to be associated with the loss of immunochemically detectable apoprotein of P450s 2C11 and 3A but with little of that of P450 2C6, in spite of their comparable DDEP-mediated functional inactivation. The loss of a approximately 50-kDa hepatic microsomal protein band along with the immunoreactive P450 3A loss strengthens the concept that such an in vivo loss indeed reflects proteolysis of the DDEP-inactivated P450. Furthermore, this propensity of DDEP-inactivated P450s 3A for proteolysis appears to correlate with the relative degree of prosthetic heme alkylation of their apoprotein rather than their functional inactivation per se. Thus, rapid degradation of apoP450s 3A was seen after DDEP treatment, which promoted extensive irreversible heme binding to apoP450s 3A, but not after exposure to allylisopropylacetamide (AIA), which inactivates these isozymes comparably, but induced minimal apoP450 3A heme alkylation. In addition, differences were observed in the relative sensitivities of proteolysis of DDEP-inactivated P450s 2C11 and 3A to hemin, which largely prevented the DDEP-induced proteolytic loss of P450 2C11 but apparently failed to prevent the loss of DDEP-inactivated P450s 3A, when coadministered with DDEP. This differential hemin sensitivity of the proteolysis of DDEP-inactivated P450 2C11, coupled with the observation that immunochemically detectable P450 2C11 loss occurs after its inactivation by both AIA and DDEP, provides compelling support for the existence of distinct proteolytic pathways for individual suicidally inactivated P450s.

Systematic exercise training results in changes in skeletal muscle that increase oxidative capacity and vascular conductance, which lead to an increase in maximal AVO2 difference. Also, maximal cardiac output is increased, largely because of an increase in maximal stroke volume. Heart rate is decreased at rest and during submaximal exercise because of increased parasympathetic tone and the effect of increased stroke volume on reflex sympathetic tone. The increases in maximal AVO2 difference and cardiac output result in increased maximal VO2, the hallmark of the dynamically trained individual. Predominant static exercise training results in fewer increases in maximal VO2 and more local muscle strength enhancements. The systematic application of cross-training can increase both cardiovascular and strength parameters, leading to enhanced athletic performance.

Schistosomiasis (bilharzia) is a parasitic disease caused by several species of schistosome worms (blood flukes). The key pathogenic event in this disease is the formation of granulomas around schistosome eggs trapped in portal venules of the liver. Granulomas are a distinctive form of chronic inflammation characterized by localized aggregation of activated macrophages around an inciting stimulus. Each granuloma evolves to form a fibrous scar; in schistosomiasis, the result is widespread hepatic fibrosis and portal hypertension. To identify the specific immune signal molecules necessary for granuloma formation, we studied schistosome infections in severe combined immunodeficient (SCID) mice, which have normal macrophages but lack functional B or T lymphocytes. Here we report that the immunoregulatory cytokine tumour necrosis factor alpha is necessary and sufficient to reconstitute granuloma formation in schistosome-infected SCID mice. Moreover, we find that the parasitic worms require tumour necrosis factor alpha for egg-laying and for excretion of eggs from the host. The implication of this latter result is that the parasite has adapted so successfully to its host that it uses a host-derived immunoregulatory protein as a signal for replication and transmission.

BACKGROUND

Transforming growth factor-beta 1 (TGF-beta 1), a potent growth modulator produced by a variety of tumor cells, as well as by platelets, has pleiotropic effects on cell-extracellular matrix interactions and may influence tumor cell invasion and metastasis.

PURPOSE

Our purpose was to characterize the effects of TGF-beta 1 on the adhesion, motility, and invasiveness of a metastatic human pulmonary carcinoma (A549 cell line) in vitro.

METHODS

A549 cells were seeded onto type I collagen gels, and invasion over a 9-day period was measured in the presence or absence of TGF-beta 1 (0.1-10 ng/mL). In addition, cell adhesion to substrata coated with type I collagen (1-100 nM) as well as haptotactic migration through filters coated with type I collagen (100 micrograms/mL) were measured following a 24-hour treatment with TGF-beta 1 (1-10 ng/mL).

RESULTS

TGF-beta 1 stimulated the invasion of A549 cells into type I collagen gels in a dose-dependent manner. Both the number of cells entering the gel and the depth of invasion into the gel were increased. In addition, the effects of TGF-beta 1 were blocked in a dose-dependent manner by a purified polyclonal IgG against TGF-beta 1 but not by normal rabbit IgG. A549 cell invasion was accompanied by dramatic changes in A549 cell morphology that included the appearance of numerous long pseudopodia, consistent with a change in the motile behavior of these cells. TGF-beta 1 stimulated by approximately fourfold the haptotactic migration of A549 cells on polycarbonate filters coated with type I collagen. The TGF-beta 1-mediated increase in invasion and motility was accompanied by a fourfold increase in A549 cell adhesion to type I collagen.

CONCLUSIONS

The results suggest that TGF-beta 1 can influence cellular recognition of extracellular matrix components and can modulate cellular adhesion and migration on these components, leading to increased invasive potential.

IMPLICATIONS

Given the wide-spread tissue distribution of TGF-beta 1 and its secretion by a variety of tumor cells as well as by platelets, TGF-beta 1 may be an important autocrineparacrine regulator of the invasive phenotype in vivo.