Augmenter of liver regeneration causes different kinetics of ERK1/2 and Akt/PKB phosphorylation than EGF and induces hepatocyte proliferation in an EGF receptor independent and liver specific manner.

BACKGROUND/AIM: Augmenter of liver regeneration (ALR) is a potent growth factor which supports liver regeneration in experimental animals. The aim of this study was to compare proliferation as well as the kinetics of ERK1/2 and Akt/PKB phosphorylation by recombinant human ALR (rhALR) and EGF in human hepatocytes and extrahepatic cells. METHODS: Kinetics of ERK1/2 and Akt/PKB phosphorylation were determined in primary human hepatocytes (phh) after stimulation with rhALR and EGF. Induction of proliferation was analyzed in phh and several cell lines of hepatic and extrahepatic origin by the MTT and [(3)H]-thymidine assay. RESULTS: The kinetics of ERK phosphorylation showed clear differences, whereby rhALR caused a transient and EGF a permanent increase during the observation period of 60 min. For both, Akt and ERK phosphorylation, EGF caused a faster effect with maximal levels observed already after 2 min, whereas rhALR caused maximal phosphorylation between 10 and 15 min. Using the EGF receptor inhibitor AG1478 we provide evidence of an EGF receptor independent induction of proliferation by rhALR. Furthermore, rhALR induced proliferation only in phh and the human liver derived cell lines HepG2 and Chang. In contrast, EGF enhanced proliferation in all analyzed cell types including cell lines of colon, bronchial, pancreatic and gastric origin (SW480, BC1, L36PL and GC1). CONCLUSION: rhALR and EGF induce different kinetics of ERK and Akt phosphorylation in human hepatocytes. The mitogenic effect of rhALR is liver specific and seems to be at least partially independent from EGF receptor mediated signaling.

A longitudinal view of triggers and thresholds of suicidal behavior in depression.

BACKGROUND: Recurrent brief depressive disorder (RBD) and major depressive disorder (MDD) share the same diagnostic picture of full-blown depression and are both associated with increased suicide attempt rates. However, longitudinal diagnostic shifts from RBD to MDD or vice versa, called "combined depression" (CD), have demonstrated a substantially higher risk of suicide attempts in epidemiologic and clinical studies. Following the stress-diathesis model of suicidal behavior, we compared possible triggers and thresholds for suicidal behavior among patients with RBD, MDD, and CD. RBD and MDD diagnoses were based on DSM-IV criteria. Furthermore, the goal of this study was to determine if impulsivity as an underlying factor could explain high suicide attempt rates in CD. METHOD: A structured clinical interview evaluating comorbid Axis I and II disorders and RBD and a battery of instruments assessing suicidal behavior were administered to 101 patients with RBD (N = 27), MDD (N = 33), or CD (N = 41). RESULTS: Patients with CD showed significantly higher (p < .05) scores on measures of suicidal behavior in comparison with RBD and MDD patients. Together with comorbid substance abuse and marital status, CD was among the highest-ranking risk factors for suicide attempts. Impulsivity was identified as a major underlying factor, predicting 80.7% of suicide attempts. CONCLUSION: CD seems to be an important clinical risk factor for the prediction of suicide attempts, similar to risk factors such as substance use disorders and borderline personality disorder. All of these factors share the same diathesis for increased impulsivity and suicidal ideation, which could explain comorbidity and suicidal behavior. The coexistence of a greater propensity for suicidal ideation and impulsivity in RBD might also explain why such patients are more prone to attempt suicide, even if they do not, in the case of RBD, meet the duration criteria for MDD.