Bilirubin Toxicity in a Neuroblastoma Cell Line N-115: II. Delayed Effects and Recovery

Abstract

Laboratory studies have demonstrated that bilirubin can affect a host of different cellular functions (1 1). Recent studies from our laboratory have shown that bilirubin toxicity in the neuroblastoma cell line N-115 was dependent on bilirubin concentration, B/A, and time of exposure (1 2). The effect on mitochondria1 function, [3H]thymidine uptake and ~~-[~'S]methionine uptake became manifest after 2 h of bilirubin exposure (12). As these vital cellular functions are affected by a short-term exposure to bilirubin, the N-115 cell line offers a good model system to study the early stages of bilirubin toxicity. The present study examines the reversibility of bilirubin toxicity in the early stages with respect to cellular function, as well as the possible delayed effects of a short-term exposure to three cellular functions, wherein no bilirubin toxicity was manifest. Contrary to the clinical situation, the present results indicate an irreversibility even in the early stages of bilirubin toxicity to the neural cell line. MATERIALS AND METHODS

Apoptosis and impairment of neurite network by short exposure of immature rat cortical neurons to unconjugated bilirubin increase with cell differentiation and are additionally enhanced by an inflammatory stimulus

“…There are only other two studies that determined neuronal recovery after a short‐term UCB exposure. Amit et al (1989) have show that after this exposure, the cells begin to display evidence of toxicity 8–24 hr after the UCB washout, indicating that UCB‐induced neuronal damage is a progressive and irreversible process. Similarly, Hankø et al (2005) described that a 6 hr‐exposure to UCB and subsequent rescue with UCB‐free medium may result in delayed cell death.…”

Reassessment of the Unbound Concentrations of Unconjugated Bilirubin in Relation to Neurotoxicity In Vitro

“…In another selected paper (15), studies were done at B F values below 5 M, but no toxicity was observed at B F values Յ 1 M. In three of the papers selected (13,14,16), the stock UCB solution was markedly supersaturated, so that precipitation and degradation likely occurred; thus, the true threshold for UCB toxicity may have been lower than the calculated B F values. Another selected paper studied B F values below 5 M, but there were no studies done at B F values between 383 and 1761 nM, so that the true threshold could not be evaluated (17).…”

Effect of 7-Nitroindazole on Bilirubin-Induced Changes in Brain Cell Membrane Function and Energy Metabolism in Newborn Piglets

“…Various in vitro [6][7][8] and in vivo [9][10][11] studies suggest that disturbance of mitochondrial function and thereby energy metabolism is an important element of the neurotoxic effects of bilirubin. Our data of reduced cerebral ATP and phosphocreatine levels in BG support this assumption.…”

“…Disruption of membrane function, compromise of energy metabolism, decreased membrane potential, alteration in enzymatic function, inhibition of protein and DNA synthesis, and excitotoxicity are some of the toxic mechanism implicated [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Among these disturbances, mitochondria might be the primary target of bilirubin toxicity [6][7][8][9][10][11], and the resultant depletion of cerebral energy stores would trigger a series of mechanisms mediating neuronal death that probably begin with membrane depolarization, accumulation of extracellular glutamate, increase in cytosolic calcium, and generation of oxygen free radicals and nitric oxide (NO) [1,15]. Particular importance for the synthesis of NO, especially by neuronal nitric oxide synthetase (nNOS), in mediating neuronal death has been suggested by many studies [15][16][17][18][19][20][21][22][23].…”