minocycline and Kernicterus

All pre-term newborns and a high proportion of term newborns develop neonatal jaundice. Neonatal jaundice is usually a benign condition and self-resolves within few days after birth. However, a combination of unfavorable complications may lead to acute hyperbilirubinemia. Excessive hyperbilirubinemia may be toxic for the developing nervous system leading to severe neurological damage and death by kernicterus. Survivors show irreversible neurological deficits such as motor, sensitive and cognitive abnormalities. Current therapies rely on the use of phototherapy and, in unresponsive cases, exchange transfusion, which is performed only in specialized centers. During bilirubin-induced neurotoxicity different molecular pathways are activated, ranging from oxidative stress to endoplasmic reticulum (ER) stress response and inflammation, but the contribution of each pathway in the development of the disease still requires further investigation. Thus, to increase our understanding of the pathophysiology of bilirubin neurotoxicity, encephalopathy and kernicterus, we pharmacologically modulated neurodegeneration and neuroinflammation in a lethal mouse model of neonatal hyperbilirubinemia. Treatment of mutant mice with minocycline, a second-generation tetracycline with anti-inflammatory and neuroprotective properties, resulted in a dose-dependent rescue of lethality, due to reduction of neurodegeneration and neuroinflammation, without affecting plasma bilirubin levels. In particular, rescued mice showed normal motor-coordination capabilities and behavior, as determined by the accelerating rotarod and open field tests, respectively. From the molecular point of view, rescued mice showed a dose-dependent reduction in apoptosis of cerebellar neurons and improvement of dendritic arborization of Purkinje cells. Moreover, we observed a decrease of bilirubin-induced M1 microglia activation at the sites of damage with a reduction in oxidative and ER stress markers in these cells. Collectively, these data indicate that neurodegeneration and neuro-inflammation are key factors of bilirubin-induced neonatal lethality and neuro-behavioral abnormalities. We propose that the application of pharmacological treatments having anti-inflammatory and neuroprotective effects, to be used in combination with the current treatments, may significantly improve the management of acute neonatal hyperbilirubinemia, protecting from bilirubin-induced neurological damage and death.

Topics: Animals; Animals, Newborn; Bilirubin; Brain Diseases; Disease Models, Animal; Hyperbilirubinemia, Neonatal; Inflammation; Kernicterus; Mice; Minocycline; Neuroimmunomodulation; Neuroprotective Agents; Neurotoxicity Syndromes; Phototherapy

Hazardous levels of bilirubin produce oxidative stress in vitro and may play a role in the genesis of bilirubin-induced neurologic dysfunction (BIND). We hypothesized that the antioxidants taurourosdeoxycholic acid (TUDCA), 12S-hydroxy-1,12-pyrazolinominocycline (PMIN), and minocycline (MNC) inhibit oxidative stress and block BIND in hyperbilirubinemic j/j Gunn rat pups that were given sulfadimethoxine to induce bilirubin encephalopathy.. At peak postnatal hyperbilirubinemia, j/j Gunn rat pups were dosed with sulfadimethoxine to induce bilirubin encephalopathy. Pups were given TUDCA, PMIN, MNC, or vehicle pretreatment (15 min before sulfadimethoxine). After 24 h, BIND was scored by using a rating scale of neurobehavior and cerebellar tissue 4-hydroxynonenal and protein carbonyl dinitrophenyl content were determined. Nonjaundiced heterozygous N/j pups served as controls.. Administration of sulfadimethoxine induced BIND and lipid peroxidation but not protein oxidation in hyperbilirubinemic j/j pups. TUDCA, PMIN, and MNC each reduced lipid peroxidation to basal levels observed in nonjaundiced N/j controls, but only MNC prevented BIND.. These findings show that lipid peroxidation inhibition alone is not sufficient to prevent BIND. We speculate that the neuroprotective efficacy of MNC against BIND involves action(s) independent of, or in addition to, its antioxidant effects.

Topics: Aldehydes; Animals; Animals, Newborn; Antioxidants; Behavior, Animal; Bilirubin; Cerebellum; Disease Models, Animal; Humans; Infant, Newborn; Jaundice, Neonatal; Kernicterus; Lipid Peroxidation; Minocycline; Motor Activity; Neuroprotective Agents; Oxidative Stress; Protein Carbonylation; Pyrazoles; Rats; Rats, Gunn; Sulfadimethoxine; Taurochenodeoxycholic Acid; Time Factors

Extreme hyperbilirubinemia is treated with double volume exchange transfusion, which may take hours to commence. A neuroprotective agent that could be administered immediately might be clinically useful. Minocycline, an anti-inflammatory and anti-apoptotic semisynthetic tetracycline, prevents hyperbilirubinemia-induced cerebellar hypoplasia in Gunn rats. Acute brainstem auditory evoked potential (BAEP) abnormalities occur after giving sulfadimethoxine to 16-day-old jaundiced Gunn rats to displace bilirubin into tissue including brain.. To assess whether minocycline is neuroprotective in this model of acute bilirubin encephalopathy.. We recorded BAEPs at baseline and 6 h after injecting sulfadimethoxine. Minocycline 0.5 mg/kg (n = 4), 5 mg/kg (n = 9), 50 mg/kg (n = 9) or 500 mg/kg (n = 3, all died) was administered 15 min before sulfadimethoxine (0 h). Controls received saline followed by either sulfadimethoxine (n = 13) or saline (n = 7).. At 6 h total plasma bilirubin decreased from 10.84 +/- 0.88 mg/dl (mean +/- SD) to 0.70 +/- 0.35 mg/dl (p <10(-9)) in all sulfadimethoxine-injected groups. At 6 h, there was complete protection against decreased amplitudes of BAEP waves II and III and increased I-II and I-III interwave intervals (brainstem conduction times corresponding to I-III and I-V in humans) with 50 mg/kg minocycline, and partial protection with lower doses.. Minocycline 50 mg/kg 15 min prior to an intervention that normally produces acute bilirubin neurotoxicity is neuroprotective in jaundiced Gunn rat pups. Further studies are needed to investigate the temporal course and mechanism of neuroprotection. Minocycline, administered immediately, may be clinically useful in treating extreme neonatal hyperbilirubinemia and preventing kernicterus. We believe our model provides an efficient in vivo model to screen and evaluate new agents that are neuroprotective against bilirubin toxicity and kernicterus.

Topics: Animals; Animals, Newborn; Anti-Bacterial Agents; Anti-Infective Agents; Bilirubin; Disease Models, Animal; Dose-Response Relationship, Drug; Evoked Potentials, Auditory, Brain Stem; Female; Jaundice; Kernicterus; Male; Minocycline; Neural Conduction; Random Allocation; Rats; Rats, Gunn; Sulfadimethoxine

Encephalopathy induced by hyperbilirubinemia in infants has been described in the medical literature for over a century but neither the cellular nor molecular mechanisms underlying bilirubin neurotoxicity are well understood. In this study, we have demonstrated that minocycline potently protects primary cultured rat cerebellar granule neurons against bilirubin neurotoxicity (IC50 approximately 2 microm) and almost completely blocks cerebellar hypoplasia and the profound loss of Purkinje and granule neurons observed in homozygous Gunn rats, a genetic model of hyperbilirubinemia-induced neurotoxicity. Minocycline-treated newborn Gunn rats had nearly equivalent numbers of viable Purkinje and granule neurons in the cerebellum as did control animals. Moreover, minocycline inhibits the bilirubin-induced phosphorylation of p38 mitogen-activated protein kinase both in vivo as well as in vitro. Taken together our data demonstrate that minocycline is able to greatly reduce bilirubin-induced neurotoxicity and suggest that minocycline's neuroprotective effects may be due in part to an inhibition of p38 mitogen-activated protein kinase activity. Our findings may lead to novel approaches for treating bilirubin-induced encephalopathy.

Topics: Animals; Anti-Bacterial Agents; Cells, Cultured; Cerebellar Cortex; Disease Models, Animal; Down-Regulation; Enzyme Inhibitors; Homozygote; Humans; Infant, Newborn; Jaundice, Neonatal; Kernicterus; Minocycline; Nerve Degeneration; Neuroprotective Agents; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Purkinje Cells; Rats; Rats, Gunn