Hypothalamic CCL2/CCR2 Chemokine System: Role in Sexually Dimorphic Effects of Maternal Ethanol Exposure on Melanin-Concentrating Hormone and Behavior in Adolescent Offspring

Clinical and animal studies show that ethanol exposure and inflammation during pregnancy cause similar behavioral disturbances in the offspring. While ethanol is shown to stimulate both neuroimmune and neurochemical systems in adults, little is known about their anatomical relationship in response to ethanol in utero and whether neuroimmune factors mediate ethanol's effects on neuronal development and behavior in offspring. Here we examined in female and male adolescent rats a specific population of neurons concentrated in lateral hypothalamus, which coexpress the inflammatory chemokine C-C motif ligand 2 (CCL2) or its receptor CCR2 with the orexigenic neuropeptide, melanin-concentrating hormone (MCH), that promotes ethanol drinking behavior. We demonstrate that maternal administration of ethanol (2 g/kg/d) from embryonic day 10 (E10) to E15, while having little impact on glia, stimulates expression of neuronal CCL2 and CCR2, increases density of both large CCL2 neurons colocalizing MCH and small CCL2 neurons surrounding MCH neurons, and stimulates ethanol drinking and anxiety in adolescent offspring. We show that these neuronal and behavioral changes are similarly produced by maternal administration of CCL2 (4 or 8 μg/kg/d, E10–E15) and blocked by maternal administration of a CCR2 antagonist INCB3344 (1 mg/kg/d, E10–E15), and these effects of ethanol and CCL2 are sexually dimorphic, consistently stronger in females. These results suggest that this neuronal CCL2/CCR2 system closely linked to MCH neurons has a role in mediating the effects of maternal ethanol exposure on adolescent offspring and contributes to the higher levels of adolescent risk factors for alcohol use disorders described in women.

SIGNIFICANCE STATEMENT Ethanol consumption and inflammatory agents during pregnancy similarly increase alcohol intake and anxiety in adolescent offspring. To investigate how neurochemical and neuroimmune systems interact to mediate these disturbances, we examined a specific population of hypothalamic neurons coexpressing the inflammatory chemokine CCL2 and its receptor CCR2 with the neuropeptide, melanin-concentrating hormone. We demonstrate in adolescent offspring that maternal administration of CCL2, like ethanol, stimulates these neurons and increases ethanol drinking and anxiety, and these effects of ethanol are blocked by maternal CCR2 antagonist and consistently stronger in females. This suggests that neuronal chemokine signaling linked to neuropeptides mediates effects of maternal ethanol exposure on adolescent offspring and contributes to higher levels of adolescent risk factors for alcohol use disorders in women.