Cell membranes of the human epidermoid cell line A431 express classical bradykinin (BK) B2 receptors, as assessed by [3H]BK binding studies. Furthermore, stimulation by BK induced a time-dependent modulation of protein kinase C (PKC) activity in A431 cells: a rapid activation (t1/2 approximately 1 min) is followed by a slow inhibition (t1/2 approximately 20 min) of PKC translocation measured by [3H]phorbol 12,13-dibutyrate binding. In addition, BK stimulated both adenylate cyclase activity in A431 membranes and accumulation of intracellular cyclic AMP (cAMP) in intact cells in a retarded manner. A possible BK-induced activation of the cAMP pathway mediated via PKC, phospholipase D, prostaglandins or Ca2+/calmodulin was excluded. A 35 kDa protein was found in A431 membranes to be specifically phosphorylated in the presence of both BK and protein kinase A (PKA). An anti-alpha s-antibody, AS 348, abolished stimulation of adenylate cyclase activity in response to BK, cholera toxin and isoprenaline, strongly suggesting the involvement of Gs proteins in the BK action. The BK-activated cAMP signalling system might be important for the observed inactivation of PKC slowly evoked by BK: the BK-induced rapid activation of PKC is decreased by dibutyryl cAMP, and the slow inhibition of PKC is prevented by an inhibitor of PKA, adenosine 3':5'-monophosphothioate (cyclic, Rp isomer). The inhibition of PKC translocation might be exerted directly at the level of PKC activation, since stimulation of phosphoinositide hydrolysis by BK was affected by neither dibutyryl cAMP nor forskolin. Thus our results provide the first evidence that A431 cells BK is able to activate two independent signal-transduction pathways via a single class of B2 receptors but two different G proteins. The lagging stimulation of the cAMP signalling pathway via Gs might serve to switch off PKC, which is rapidly activated via Gq-mediated stimulation of phosphoinositide hydrolysis.

In the rat pheochromocytoma cell line PC-12, bradykinin (BK) stimulated phosphatidylinositol hydrolysis by 4-5-fold and, additionally, intracellular cAMP accumulation by approx. 1.6-fold. EC50 values for BK were 3 nM and 2 nM respectively. The BK-induced increase in cAMP accumulation was paralleled by a 1.6-fold increase in protein kinase A (PKA) activity. The time course of BK-stimulated inositol phosphate formation was rapid (t1/2<1 min), whereas the BK-induced cAMP accumulation was lagging (t1/2 approx. 6 min). The effect of BK on the cAMP pathway was independent of pertussis toxin, excluding an indirect stimulation of adenylate cyclase via betagamma-complexes from Gi or Go proteins. Two different protein kinase C (PKC) inhibitors, bisindolylmaleimide and Ro 31-820, failed to prevent BK-induced cAMP accumulation, and exclude PKC as mediator of BK action on adenylate cyclase. In contrast, the stimulatory effect of BK on cAMP accumulation was completely abolished by two calmodulin antagonists, chlorpromazine and ophiobolin, suggesting an indirect, Ca2+/calmodulin-mediated effect of BK on the cAMP pathway. In addition, exposure of PC-12 cells to BK resulted in a translocation of the PKC isoforms alpha, delta, epsilon and zeta displaying different kinetics. The BK-induced translocations of the PCDs alpha and delta were rapid and biphasic, whereas the PKCs epsilon and zeta revealed a slower and slightly transient translocation in response to BK. The BK-elicited translocation of PKCepsilon, but not that of the PKCs alpha, delta and zeta, was prevented by two different inhibitors of adenylate cyclase, 2',5'-dideoxyadenosine and MDL-12,330A, as well as the PKA inhibitor adenosine 3':5'-monophosphothioate. These findings suggest that the BK-induced translocation of novel (n)PKCepsilon is mediated via the cAMP pathway. Since nPKCepsilon appears to regulate neurite outgrowth in PC-12 cells [Hundke, McMahon, Dadgar and Messing (1995) J. Biol. Chem. 270, 30134-30140] our results provide evidence for a novel signalling mechanism that might be involved in BK-induced neuronal differentiation of PC-12 cels.

The aim of our study was to assess the cumulative 5-year diagnoses of CIN2, CIN3 or invasive cervical cancer (CIN2+) after concurrent screening by high-risk HPV test and Pap smear in a primary screening setting. Four thousand thirty-four women from Eastern Thuringia/Germany were recruited from 1996 to 1998 for baseline screening that included routine cytology, high-risk HPV testing by consensus primer PCR GP5+/6+ and routine colposcopy. After a median of 59 months 3,153 women participated in final screening using identical methods. Women with abnormal cytology or colposcopy or a positive high-risk HPV test at any time during the study period were recalled for expert colposcopy and histologic verification. CIN2+ was detected in 160 women resulting in a cumulative 5-year proportion of 4.4% (95% CI: 3.7-5.0%). Of 3,702 women who were high-risk HPV negative at baseline, 34 (1.1-95% CI: 0.7-1.4%) had either prevalent CIN2+ or developed CIN2+ within the observation period. HPV/cytology double negatives at baseline were at lowest risk for CIN2+ (1.0-95% CI: 0.7-1.4%) compared to screening positives (16.8-100% depending on combined test results). The 5-year negative predictive value in HPV2/Cyto2 women was 99.0% (95% CI: 98.6-99.3%). This suggests that a prolongation of the screening intervals in this group is feasible. However, it should be noted that 1 woman developed a microinvasive carcinoma within the observation period. Moreover, 2 women with prevalent cancer were missed by both tests. The prognostic relevance of concurrent highrisk HPV/cytology screening needs to be verified further by randomized trials. ' 2005 Wiley-Liss, Inc.Key words: cervical cancer; high-risk HPV; cytology; predictive value Changes within the current primary screening setting for prevention of cervical cancer are under active discussion. It has been shown that infections with high-risk human papillomaviruses are carcinogenic.1 However, before a HPV test can be recommended for screening the efficiency and cost-effectiveness of the new system has to be demonstrated. Whereas higher sensitivity and negative predictive value of HPV testing has been shown in several, mainly cross-sectional studies, the long-term impact on incidence and mortality has been evaluated in models only.2,3 Thus, the current recommendations of various scientific societies and expert groups are controversial. The IARC working group on efficacy of cervical cancer screening concluded that there is sufficient evidence that HPV testing can reduce mortality from cervical cancer. However, further work has to be done to have an affordable, simple and reliable test.4 So far, no updated, comprehensive model calculations for the cost-effectiveness of HPV testing have been published for Europe since important data are still lacking. Our study funded exclusively by the government may add additional knowledge to this important issue of women's health.We followed a cohort of women originally recruited in the scope of a HPV diagnostic study 5 over a period of about 5 years to prove the ...

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