Günther Konwalinka

AGE DEPENDENT APOPTOSIS AND LOSS OF RHABDOSPHINCTER CELLS

PURPOSE To our knowledge the exact age dependent morphological and functional changes of the sphincter mechanism have not been investigated. Therefore, cell densities of the urethra and the urethral rhabdosphincter across various age groups, and the appearance of apoptosis were examined to explore the changes in these structures during the aging process. MATERIALS AND METHODS Specimens were obtained from 16 male and 7 female cadavers 5 weeks to 92 years old. Histological sections were taken from 3 different levels of the rhabdosphincter and urethra. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling method was used to detect apoptosis in the urethra and rhabdosphincter. In all specimens relative volume densities of the striated muscle fibers, apoptotic indexes and diameters of the rhabdosphincter and urethra were determined. RESULTS An age dependent increase of apoptosis of the striated muscle fibers of the rhabdosphincter led to a dramatic decrease in the number of striated muscle cells. In the 5-week-old neonate 87.6% and in the 91-year-old woman 34.2% of the rhabdosphincter consisted of striated muscle cells. Overall, a direct linear correlation between the age of the specimens and decrease in volume densities of the striated muscle cells was evident. CONCLUSIONS The dramatic decrease in the number of striated muscle cells in the rhabdosphincter of the elderly due to apoptosis represents the morphological basis for the high incidence of stress incontinence in this population.

Urinary incontinence in the elderly and age-dependent apoptosis of rhabdosphincter cells

With advancing age, a progressive and age-dependent decrease of the density of striated muscle cells can be observed in the rhabdosphincter. This continuous loss of striated muscle cells due to apoptosis may finally lead to urinary incontinence.

The immunomodulator FTY720 interferes with effector functions of human monocyte-derived dendritic cells

The potent immunomodulator FTY720 elicits immunosuppression via acting on sphingosine 1‐phosphate receptors (S1PR), thereby leading to an entrapment of lymphocytes in the secondary lymphoid tissue. To elucidate the potential in vitro effects of this drug on human monocyte‐derived DC, we used low nanomolar therapeutic concentrations of FTY720 and phosphorylated FTY720 (FTY720‐P) and investigated their influence on DC surface marker expression, protein levels of S1PR and DC effector functions: antigen uptake, chemotaxis, cytokine production, allostimulatory and Th‐priming capacity. We report that both FTY720 and FTY720‐P reduce chemotaxis of immature and mature DC. Mature DC generated in the presence of FTY720 or FTY720‐P showed an impaired immunostimmulatory capacity and reduced IL‐12 but increased IL‐10 production. T cells cultured in the presence of FTY720‐ or FTY720‐P‐treated DC showed an altered cytokine production profile indicating a shift from Th1 toward Th2 differentiation. In treated immature and mature DC, expression levels for two S1PR proteins, S1P1 and S1P4, were reduced. We conclude that in vitro treatment with FTY720 affects DC features that are essential for serving their role as antigen‐presenting cells. This might represent a new aspect of the overall immunosuppressive action of FTY720 and makes DC potential targets of further sphingolipid‐derived drugs.

Changes of mitochondrial respiration, mitochondrial content and cell size after induction of apoptosis in leukemia cells.

Mitochondrial damage with release of cytochrome c is implicated in cell death signalling pathways. To examine mitochondrial function in apoptotic cells, we applied high-resolution respirometry to human leukemia cells arrested in the G1- and S-phase by exposure to the glucocorticoid dexamethasone and nucleotide analogue gemcitabine. At 30% apoptosis, opposite effects were observed on respiratory capacity (71% and 131% of controls, respectively). These changes correlated with alterations in cell size, cytosolic, and mitochondrial marker enzymes. Mitochondrial ATP production and membrane potential were maintained in all treatments, as deduced from high respiratory uncoupling control ratios (UCR). Bcl-2 over-expression did not prevent apoptosis after gemcitabine-treatment, but protected dexamethasone-treated cells from apoptosis, without fully preventing the decline of respiration and cell size. These results, therefore, provide conclusive evidence that alterations in respiratory capacity and enzyme activities per cell are mainly caused by opposite changes in cell size, occurring upon cell cycle arrest triggered by dexamethasone and gemcitabine in the early phase of apoptosis.

Increased lactate production follows loss of mitochondrial membrane potential during apoptosis of human leukaemia cells

Acute tumour‐lysis syndrome (ATLS) is a frequently fatal complication after cytoreductive leukaemia therapy. Lactic acidosis is associated with ATLS and its extent is correlated with the severity of ATLS. In the course of cytoreductive therapy, apoptosis is induced in tumour cells, which results in loss of mitochondrial function. We hypothesize that loss of mitochondrial function leads to compensatory glycolysis, which is the main cause of lactate accumulation and acidosis. We tested this hypothesis using the model of glucocorticoid‐induced apoptosis in the human acute lymphoblastic leukaemia cell line CCRF‐CEM. After induction of glucocorticoid‐induced apoptosis, a biphasic course of lactate production was observed. Prior to the onset of apoptosis, i.e. prior to the loss of membrane potential, lactate production was reduced. However, subsequent to loss of mitochondrial membrane potential a massive increase in lactate production was observed (15·5 ± 0·5 versus 10·17 ± 0·09 mmol/106 cells, P = 0·001). We also demonstrated that inhibition of respiratory chain activity by antimycin A resulted in excess lactate production. In the model cell line used, conditional bcl‐2 expression delayed glucocorticoid‐induced apoptosis by protecting against loss of mitochondrial membrane potential; bcl‐2 expression delayed the increase in lactate production and had no effect on the pre‐apoptotic drop in lactate production. Apoptosis‐induced lactate production was also observed in other cell lines (HL60, THP1 and OPM2) with various cytotoxic agents [doxorubicin, gemcitabine and vumon (VM26)]. Thus, the data suggest that lactate acidosis can be caused by apoptotic loss of mitochondrial function and massive apoptosis of a tumour mass via lactic acidosis may be the essential pathological event in ATLS.

The safety profile of low-dose cladribine in refractory rheumatoid arthritis : A pilot trial

Cladribine (2-chlorodeoxyadenosine, 2-CdA) is a newer purine analog with specific toxicity to lymphocytes. As lymphocytes play a major role in rheumatoid arthritis (RA), we assessed the safety profile of low-dose 2-CdA in patients who were refractory to more than three disease-modifying drugs. Five patients were given a subcutaneous dosage of 0.05 mg/kg 2-CdA weekly over a period of 8 weeks. Of the lymphocyte subsets, both T and B cells decreased below the normal range, whereas natural killer cells remained stable. These changes were the only side-effects noted during treatment and 4 weeks afterwards. In one patient a pacemaker was implanted for reasons unlikely to be related to 2-CdA administration. We conclude that even low-dose 2-CdA (0.05 mg/kg) can decrease T and B cell populations in patients with refractory RA, but other side-effects are unlikely. For assessing the possible clinical efficacy of low-dose 2-CdA further studies are warranted.

Interferon-alpha-2C and LD ara-C for the treatment of patients with CML: Results of the austrian multicenter phase II study

Small pilot studies of patients with CML have reported on encouraging response rates after treatment with interferon-alpha (IFNalpha) in combination with low-dose cytosine arabinoside (LD ara-C). We therefore initiated a multi-center phase II trial in order to investigate the efficacy and tolerability of this combination in newly diagnosed patients with Ph-positive chronic myelogenous leukemia (CML). Eighty-four patients were treated with IFN-alpha-2c at daily subcutaneous doses of 3.5 MU and LD ara-C added subcutaneously for 10 days every month at a dose of 10 mg/m2, following an initial reduction of WBC to less than 20 x 10(9)/l with hydroxyurea (HU). Within a median observation period of 28 (5-59) months the patients received a median of 7 (1-35) IFNalpha and LD ara-C cycles. Treatment was stopped due to side effects in 16 cases (19%) and to primary or secondary treatment failure in 38 cases (45%). In 45 patients (54%) complete hematological response (CHR) was achieved; in 39 patients (46%) cytogenetic responses including 15 (18%) complete cytogenetic responses (CHR) were observed. Median duration of cytogenetic responses was 15 months. Relapses were seen in 8/15 patients (53%) with complete cytogenetic remission (CCR), in 3/6 patients (50%) with partial cytogenetic response and in 9/18 patients (50%) with minor cytogenetic response. In conclusion, the combination of IFNalpha and LD ara-C resulted in encouraging rates of hematological and cytogenetic responses in patients with CML with low to moderate toxicity.

Inhibitory effects of the nucleoside analogue gemcitabine on prostatic carcinoma cells

Gemcitabine (2≺,2≺difluoro‐2≺deoxycytidine, dFdC) is a synthetic antimetabolite of the cellular pyrimidine nucleotide metabolism. In a first series of in vitro experiments, the drug showed a strong effect on the proliferation and colony formation of the human androgen‐sensitive tumor cell line LNCaP and the androgen‐insensitive cell lines PC‐3 and DU‐145. Maximal inhibition occurred at a dFdC concentration as low as 30 nM. In contrast to the cell lines which were derived from metastatic lesions of prostate cancer patients, no inhibitory effects were found in normal primary prostatic epithelial cells at concentrations up to 100 nM. The effect of gemcitabine was reversed by co‐administration of 10–100 μM of its natural analogue deoxycytidine. In view of a future clinical application of this anti‐tumor drug in advanced prostatic carcinoma, we have compared the effect of gemcitabine on prostatic tumor cells with that on bone marrow granulopoietic‐macrophagic progenitor cells, because neutropenia is a common side effect of gemcitabine treatment. The time course of action on the two kinds of cells was markedly different. Colony formation of tumor cells was inhibited by two thirds at a gemcitabine concentration of about 3.5 nM. The same effect on granulopoietic‐macrophagic progenitor cells required a concentration of 9 nM. Co‐administration of deoxycytidine to gemcitabine‐treated tumor cell cultures completely antagonized the effect of gemcitabine whereas addition of deoxycytidine after 48 hr of gemcitabine treatment could not prevent gemcitabine action on the tumor cells. In contrast, more than half of the granulopoietic‐macrophagic progenitor cells could still be rescued by deoxycytidine administration after 48 hr. These findings and the marked difference in the susceptibility of neoplastic and normal prostatic cells suggest that gemcitabine is a promising substance which should be further evaluated as to its efficacy in the treatment of advanced prostatic carcinoma.

2′,2′-Difluorodeoxycytidine (Gemcitabine) Induces Apoptosis in Myeloma Cell Lines Resistant to Steroids and 2-Chlorodeoxyadenosine (2-CdA)

The paucity of effective cytotoxic agents for the treatment of steroid resistant multiple myeloma explains the ongoing search for alternative substances for chemotherapy of this disease. In the present study, the purine antagonist 2‐chlorodeoxyadenosine (2‐CdA, cladribine) and the pyrimidine antagonist 2′,2′‐difluorodeoxycytidine (gemcitabine) were tested on four myeloma cell lines (i.e., U 266, OPM 2, RPMI 8226, IM 9), one plasma cell leukemia cell line (HS Sultan) and a myeloid control cell line (HL 60), all of which are resistant to 10−6 M dexamethasone. Gemcitabine has been found to be promising in the chemotherapy of other tumors with low proliferative activity, but its effectiveness against myeloma cells has not been analyzed so far. In our tests, gemcitabine induced a significant degree of apoptosis in all cell lines investigated. After incubation for 48 h with 10 μM gemcitabine, the median numbers of apoptotic cells were in the range of 45% in the OPM 2 and 79% in the U 266 cell line. All of the investigated cell lines were responsive to concentrations of 10 μM gemcitabine even after an exposure of only 30 min, three of them (U 266, HS Sultan, IM 9) also responded to a concentration of 10 nM. Higher concentrations and longer exposure times were necessary to suppress the growth of normal hematopoietic bone marrow progenitor cells. In contrast to gemcitabine, standard concentrations of 2‐CdA (i.e., 30 and 300 nM) failed to induce a significant degree of apoptosis in the cell lines investigated but inhibited the growth of myeloid progenitor cells.

A regulatory role of activated T-lymphocytes on human megakaryocytopoiesis in vitro

Cellular interactions responsible for regulating in vitro megakaryocytopoiesis were studied using a microagar culture system which permits the simultaneous proliferation of human megakaryocytic progenitor cells (CFU‐M) and T‐lymphocytic colonies (CFU‐TL). The proliferation of these colony types depends mainly on two factors: phytohaemagglutinin (PHA) and erythropoietin (EP). The direct addition of increasing PHA concentrations to the liquid overlayer resulted in a parallel increase of CFU‐M and CFU‐TL. If the T‐lymphocytes were removed by an E‐rosetting technique a marked diminution of CFU‐M and CFU‐TL numbers was observed. However, monocyte depletion resulted in a marked augmentation of CFU‐M proliferation compared to unfractionated mononuclear cells. In order to confirm that the reduction of CFU‐M proliferation observed after T‐depletion was primarily mediated by the absence of T‐lymphocytes, we have co‐cultured different concentrations of previously removed autologous T‐lymphocytes with a constant number of T‐depleted bone marrow cells. A parallel increase of CFU‐TL and CFU‐M was found if 0.75‐7.5 × 104 T‐lymphocytes were added to the culture. In conclusion, our results indicate that activated T‐lymphocytes augment proliferation of human bone marrow CFU‐M and that monocytes are less important for the growth of megakaryocytic colonies.