PYRAMIDAL NEURONS:
We provided encyclopedic transcriptional hippocampal profiling of mice treated with rhEPO. Based on ~108,000 single nuclei, we unmasked multiple pyramidal lineages with their comprehensive molecular signatures. By temporal profiling and gene regulatory analysis, we built a developmental trajectory of CA1 pyramidal neurons derived from multiple predecessor lineages and elucidated gene regulatory networks underlying their fate determination. With EPO as ꞌtoolꞌ, we discovered novel populations of newly differentiating pyramidal neurons, overpopulating to ~200% upon rhEPO with upregulation of genes crucial for neurodifferentiation, dendrite growth, synaptogenesis, memory formation, and cognition. Using a Cre-based approach to visually distinguish pre-existing from newly formed pyramidal neurons for patch-clamp recordings, we learned that rhEPO treatment differentially affects excitatory and inhibitory inputs. Our findings provide mechanistic insight into how EPO modulates neuronal functions and networks.
ERC Paper:
Singh et al (2023): EPO re-wires cognition-associated transcriptional networks. Nat Commun 21;14(1):4777.
INTERNEURONS:
Patients with severe neuropsychiatric disease display cognitive impairment and perturbed excitatory-inhibitory balance in brain. Effects in juvenile mice can elucidate how EPO might aid in rectifying hippocampal transcriptional networks and synaptic structures of pyramidal lineages, conceivably explaining mitigation of neuropsychiatric diseases. An imminent conundrum is how EPO restores synapses by involving interneurons. By analysing ~12,000 single-nuclei transcriptomic data, we generated a comprehensive molecular atlas of hippocampal interneurons, resolved into 15 interneuron subtypes. We studied molecular alterations upon rhEPO and saw that gene expression changes relate to synaptic structure, trans-synaptic signaling and intracellular catabolic pathways. Putative ligand-receptor interactions between pyramidal and inhibitory neurons, regulating synaptogenesis, are altered upon rhEPO. An array of in/ex vivo experiments confirms that specific interneuronal populations exhibit reduced dendritic complexity, synaptic connectivity, and changes in plasticity-related molecules. Metabolism and inhibitory potential of interneuron subgroups are compromised, leading to greater excitability of pyramidal neurons. To conclude, improvement by rhEPO of neuropsychiatric phenotypes may partly owe to restrictive control over interneurons, facilitating re-connectivity and synapse development.
ERC Paper:
Curto et al (2024): EPO restrains the inhibitory potential of interneurons in the mouse hippocampus. Mol Psychiatry 15. doi: 10.1038/s41380-024-02528-2
HUMAN HYPOXIA (1):
Hypoxia is increasingly recognized as an important physiological driving force. A specific transcriptional program, induced by decrease in oxygen (O2) availability, e.g. inspiratory hypoxia at high altitude, allows cells to adapt to lower O2 and limited energy metabolism. This transcriptional program is partly controlled by and partly independent of hypoxia-inducible factors. Remarkably, this same transcriptional program is stimulated in brain by extensive motor-cognitive exercise, leading to relative decrease in O2 supply, compared to the acutely augmented O2 requirement. We have coined the term ꞌfunctional hypoxiaꞌ for this important demand-responsive, relative reduction in O2 availability. Functional hypoxia seems to be critical for enduring adaptation to higher physiological challenge that includes substantial 'brain hardware upgrade', underlying advanced performance. Hypoxia-induced EPO expression in brain likely plays a decisive role in these processes which can be imitated by rhEPO treatment.
This article reviews present hints of how inspiratory O2 manipulations can potentially contribute to enhanced brain function. It thereby provides the ground for exploiting moderate inspiratory plus functional hypoxia to treat individuals with brain disease. Finally, it sketches a planned multi-step pilot study in healthy volunteers and first patients, about to start, aiming at improved performance upon motor-cognitive training under inspiratory hypoxia.
ERC Paper:
Ehrenreich et al (2023): Exploiting moderate hypoxia to benefit patients with brain disease: molecular mechanisms and translational research in progress. Neuroprotection 1:55‐65.
HUMAN HYPOXIA (2):
Major players in the hypoxia response are hypoxia-inducible factors (HIF) and associated prolyl-hydroxylases. HIF are transcription factors, stabilized by low O2 accessibility, and control expression of a multitude of genes. Changes in oxygen, however, can also be sensed via other pathways, among them the thiol-oxidase ADO. Considering the far-reaching biological response to hypoxia, hitherto mostly observed in rodents, we initiated a translational project, combining mild to moderate inspiratory with functional hypoxia. We had identified this combination earlier to benefit motor-cognitive attainment in mice. A total of 20 subjects were included, 13 healthy individuals and 7 patients with depression and/or autism spectrum disorder. Here, we show that motor-cognitive training under inspiratory hypoxia (12% O2) for 3.5 hours daily over 3 weeks is optimally tolerated. We present first signals of beneficial effects on general well-being, cognitive performance, physical fitness and psychopathology. EPO in serum increases under hypoxia and flow cytometry analysis of blood reveals several immune cell types to be mildly modulated by hypoxia. To obtain reliable information regarding the ′add-on′ value of inspiratory on top of functional hypoxia, induced by motor-cognitive training, a single-blind study - with versus without inspiratory hypoxia - is essential and outlined here.
ERC Paper:
Mennen et al (2024). Tolerability and first hints for potential efficacy of motor‐cognitive training under inspiratory hypoxia in health and neuropsychiatric disorders: A translational viewpoint. Neuroprotection 2: 1–15.
