Daily Rhythms in the IGF-1 System in the Liver of Goldfish and Their Synchronization to Light/Dark Cycle and Feeding Time

Is there direct photoentrainment in the goldfish liver? Wavelength-dependent regulation of clock genes and investigation of the opsin 7 family

Widespread direct photoentrainment in zebrafish peripheral tissues is linked to diverse non-visual opsins. To explore whether this broadly distributed photosensitivity is specific to zebrafish or is a general teleost feature, we investigated hepatic photosynchronization in goldfish. First, we focused on the opsin 7 family (OPN7, a key peripheral novel opsin in zebrafish), investigating its presence in the goldfish liver. Subsequently, we studied whether light can directly entrain the goldfish liver and retina clocks. Silico analysis revealed seven OPN7 paralogs from four gene families, suggesting expansion through whole-genome and tandem duplications. The paralogs of families OPN7a, OPN7b, and OPN7d were mainly localized in neural tissues, while OPN7c paralogs were more abundant in peripheral tissues-including the liver-suggesting divergent roles. Light (independently of the wavelength employed) directly induced the per2a clock gene in the retina both in vivo and in vitro, confirming expected photoentrainment. However, in the liver, photoinduction of per1a and cry1a only occurred in vivo, not in vitro. These results suggest an indirect light-entrainment mechanism of the goldfish hepatic clock, possibly mediated by other oscillators or photosensitive organs. Our findings challenge the assumption of widespread direct photosensitivity in the peripheral tissues of teleosts. Further research is needed to understand the role of tissue-specific photoentrainment and non-visual opsins in diverse teleost species.

Review: therapeutic approaches for circadian modulation of the glioma microenvironment

High-grade gliomas are malignant brain tumors that are characteristically hard to treat because of their nature; they grow quickly and invasively through the brain tissue and develop chemoradiation resistance in adults. There is also a distinct lack of targeted treatment options in the pediatric population for this tumor type to date. Several approaches to overcome therapeutic resistance have been explored, including targeted therapy to growth pathways (ie. EGFR and VEGF inhibitors), epigenetic modulators, and immunotherapies such as Chimeric Antigen Receptor T-cell and vaccine therapies. One new promising approach relies on the timing of chemotherapy administration based on intrinsic circadian rhythms. Recent work in glioblastoma has demonstrated temporal variations in chemosensitivity and, thus, improved survival based on treatment time of day. This may be due to intrinsic rhythms of the glioma cells, permeability of the blood brain barrier to chemotherapy agents, the tumor immune microenvironment, or another unknown mechanism. We review the literature to discuss chronotherapeutic approaches to high-grade glioma treatment, circadian regulation of the immune system and tumor microenvironment in gliomas. We further discuss how these two areas may be combined to temporally regulate and/or improve the effectiveness of immunotherapies.