[Liver injury induced by immune checkpoint inhibitor-therapy : Example of an immune-mediated drug side effect]. / Leberschaden durch Therapie mit Immun-Checkpoint-Inhibitoren : Beispiel einer immunvermittelten Medikamentennebenwirkung.

BACKGROUND: Drug-induced liver injury is increasing, especially in elderly patients with polymedication and multimorbidity. OBJECTIVES: Clinicopathologic correlation of immune-mediated liver injury, specifically liver injury following therapy with immune checkpoint inhibitors against PD-1, PDL-1, and CTLA4. METHODS: Histologic assessment of liver biopsies of nine patients after therapy with immune checkpoint inhibitors and correlation with clinical parameters. RESULTS: In all nine patients, liver injury was apparent after variable administration of immune checkpoint inhibitors. Transaminase levels were increased up to a maximum of 3818 U/l. Liver histology showed liver injury resembling autoimmune hepatitis respective cholangitis. In two patients, veno-occlusive disease was seen. Corticosteroid therapy was initiated in eight patients, subsequently four patients showed decreasing transaminases and five patients died of tumor progress. In three patients, it remains unclear whether liver injury by immune checkpoint inhibitors may have ultimately contributed to the fatal course, especially in one patient with liver cirrhosis and hepatocellular carcinoma. CONCLUSIONS: Therapy with immune checkpoint inhibitors may lead to potentially fatal immune phenomena in susceptible patients, which may affect liver and/or other organs independently. Other causes of hepatopathy need to be ruled out clinically and/or histologically.

NF-kappaB signaling in cerebral ischemia.

The transcription factor NF-kappaB is a key regulator of hundreds of genes involved in cell survival and inflammation. There is ample evidence that NF-kappaB is activated in cerebral ischemia, mainly in neurons. Despite its well known role as an antiapoptotic factor, in cerebral ischemia NF-kappaB contributes to neuronal cell death, at least if the ischemia is severe enough to lead to irreversible brain damage. In contrast, NF-kappaB also seems to be responsible for the preconditioning effect of a transient and sublethal ischemia, perhaps by dampening its own subsequent full activation. Among the five NF-kappaB subunits, RelA and p50 are responsible for the detrimental effect in cerebral ischemia. Activation of NF-kappaB signaling is mediated by the upstream kinase inhibitor of kappaB kinase and is triggered by hypoxia, reactive oxygen species, and several inflammatory mediators. Interestingly, the complex NF-kappaB signaling pathway provides drug targets at several levels. Modulation of NF-kappaB signaling has the potential to interrupt multiple inflammatory and apoptotic mechanisms through one specific molecular target.

Acute inhibition of TAK1 protects against neuronal death in cerebral ischemia.

Neuronal apoptosis contributes to ischemic brain damage and neurodegenerative disorders. Key regulators of neuronal apoptosis are the transcription factor NF-κB and the MAP kinases p38/MAPK and JNK, which share a common upstream activator, the mitogen-activated protein kinase kinase kinase (MAP3K) TGFß-activated kinase 1 (TAK1). Here we investigate the function of TAK1 in ischemia-induced neuronal apoptosis. In primary cortical neurons, TAK1 was activated by oxygen glucose deprivation (OGD), an in vitro model of cerebral ischemia. We found that short-term inhibition of TAK1 protected against OGD in vitro and reduced the infarct volume after middle cerebral artery occlusion in vivo. Prolonged inhibition or deletion of the TAK1 gene in neurons was, however, not protective. Short-term, but not prolonged inhibition of TAK1 interfered with the activation of p38/MAPK and JNK by OGD, the induction of the pro-oxidative genes Cox-2, Nox-2, and p40(phox), and the formation of superoxide. We found that prolonged TAK1 inhibition upregulated another MAP3K, apoptosis signal-regulating kinase-1, which is able to compensate for TAK1 inhibition. Our study demonstrates that TAK1 is a central target for short-term inhibition of key signaling pathways and neuroprotection in cerebral ischemia.

A transgenic approach to identify thyroxine transporter-expressing structures in brain development.

Transporters are essential in thyroid hormone metabolism. Thyroxine (T4) is transported by solute carrier organic anion transporter 1c1 (SLCO1C1, OATP14) into the adult brain, where T4 is converted to 3,5,3'-triiodothyronine (T3). In adults, SLCO1C1 expression is found in two brain barrier structures: the blood-brain barrier (BBB) and choroid plexus. However, little is known about how T4 is transported in the developing brain, when the BBB is not yet completely formed. We employed bacterial artificial chromosome recombineering to generate transgenic mice carrying Cre recombinase in the Slco1c1 locus (Slco1c1-Cre mice). In Slco1c1-Cre mice Cre was expressed at the sites that have been previously reported for SLCO1C1 in adults. To trace Cre expression during development, we crossed Slco1c1-Cre transgenic mice with Rosa26 reporter mice. ß-galactosidase staining showed Cre activity in neurones of various brain structures, such as cortical layer 2/3 and the hippocampus, suggesting transient Slco1c1 expression during brain development. At embryonic day15, SLCO1C1 was expressed at the same site as TBR2, a marker of neuronal progenitors. Neurones that express SLCO1C1 during their development could be T4 sensitive. In support of this hypothesis, hypothyroxinaemia induced by propylthiouracil treatment of dams decreased the number of ß-galactosidase-positive neurones in cortical layer 2/3 of newborn Slco1c1-Cre/Rosa26 mice. In conclusion, by generating Slco1c1-Cre transgenic mice, we demonstrated that SLCO1C1 is expressed in the neuronal cell lineage during brain development. Expression of SLCO1C1 may underlie the extraordinary sensitivity of specific neuronal populations to hypothyroxinaemia.