Intertwined regulators: hypoxia pathway proteins, microRNAs, and phosphodiesterases in the control of steroidogenesis

HIF1α controls steroidogenesis under acute hypoxic stress

BACKGROUND

Hypoxia is a critical physiological and pathological condition known to influence various cellular processes, including steroidogenesis. While previous studies, including our own, have highlighted the regulatory effects of Hypoxia-Inducible Factor 1α (HIF1α) on steroid production, the specific molecular mechanisms remain poorly understood. This study investigates the role of hypoxia and HIF1α in steroid biosynthesis across multiple experimental models during acute exposure to low oxygen levels.

METHODS

To assess the extent to which acute hypoxia modulates steroidogenesis, we employed several approaches, including the Y1 adrenocortical cell line, and a conditional HIF1α-deficient mouse line in the adrenal cortex. We focused on various regulatory patterns that may critically suppress steroidogenesis.

RESULTS

In Y1 cells, hypoxia upregulated specific microRNAs in a HIF1α-dependent manner, resulting in the suppression of mRNA levels of critical steroidogenic enzymes and a subsequent reduction in steroid hormone production. The hypoxia/HIF1α-dependent induction of these microRNAs and the consequent modulation of steroid production were confirmed in vivo. Notably, using our adrenocortical-specific HIF1α-deficient mouse line, we demonstrated that the increase in miRNA expression in vivo is also directly HIF1α-dependent, while the regulation of steroidogenic enzymes (e.g., StAR and Cyp11a1) and steroid production occurs at the level of protein translation, revealing an unexpected layer of control under hypoxic/HIF1 α conditions in vivo.

CONCLUSIONS

These findings elucidate the molecular mechanisms underlying acute hypoxia/HIF1α-induced changes in steroid biosynthesis and may also be useful in developing new strategies for various steroid hormone pathologies.

Regulation of B-cell function by miRNAs impacting Systemic lupus erythematosus progression

Systemic lupus erythematosus (SLE) is a complex autoimmune disease marked by abnormal B-cell proliferation and increased autoantibodies. miRNAs play a crucial role in regulating B-cell dysfunction and SLE pathology. miRNAs influence DNA methylation, B-cell activation, and gene expression, contributing to SLE pathogenesis. miRNAs impact B cells through key processes like proliferation, differentiation, tolerance, and apoptosis. miRNAs also exacerbate inflammation and immune responses by modulating Interleukin 4 (IL-4), IL-6, and interferon cytokines. Autophagy, a key degradation mechanism, is also regulated by specific miRNAs that impact SLE pathology. This article explores the role of multiple miRNAs in regulating B-cell development, proliferation, survival, and immune responses, influencing SLE pathogenesis. miRNAs like miR-23a, the miR-17 ∼ 92 family, and miR-125b/miR-221 affect B-cell development by regulating transcription factors, signaling pathways, and cell cycle genes. miRNAs such as miR-181a-5p and miR-23a-5p are differentially regulated across developmental stages, emphasizing their complex regulatory roles in B-cell biology. This article synthesizes miRNA-B cell interactions to offer new strategies and directions for SLE diagnosis and treatment.

From Vessels to Neurons-The Role of Hypoxia Pathway Proteins in Embryonic Neurogenesis

Embryonic neurogenesis can be defined as a period of prenatal development during which divisions of neural stem and progenitor cells give rise to neurons. In the central nervous system of most mammals, including humans, the majority of neocortical neurogenesis occurs before birth. It is a highly spatiotemporally organized process whose perturbations lead to cortical malformations and dysfunctions underlying neurological and psychiatric pathologies, and in which oxygen availability plays a critical role. In case of deprived oxygen conditions, known as hypoxia, the hypoxia-inducible factor (HIF) signaling pathway is activated, resulting in the selective expression of a group of genes that regulate homeostatic adaptations, including cell differentiation and survival, metabolism and angiogenesis. While a physiological degree of hypoxia is essential for proper brain development, imbalanced oxygen levels can adversely affect this process, as observed in common obstetrical pathologies such as prematurity. This review comprehensively explores and discusses the current body of knowledge regarding the role of hypoxia and the HIF pathway in embryonic neurogenesis of the mammalian cortex. Additionally, it highlights existing gaps in our understanding, presents unanswered questions, and provides avenues for future research.