Sex- and region-biased depletion of microglia/macrophages attenuates CLN1 disease in mice

Berve K, West BL, Martini R, Groh J

Journal of Neuroinflammation · 28 Oct 2020 · doi: 10.1186/s12974-020-01996-x

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Neuroinflammation can have devastating degenerative consequences in the central nervous system when the immune system attacks the body’s own cells. This paper shows that neuroinflammation can be attenuated by treatment with proper pharmacological substances. This has beneficial consequences from the cellular to the behavioral level. For example, Berve et al show with our OptoDrum that vision degenerates strongly in Ppt1-/- mice due to optic nerve atrophy. Pharmacological inhibition of innate immune cells ameliorates those effects

Abstract

Background. The neuronal ceroid lipofuscinoses (CLN diseases) are fatal lysosomal storage diseases causing neurodegeneration in the CNS. We have previously shown that neuroinflammation comprising innate and adaptive immune reactions drives axonal damage and neuron loss in the CNS of palmitoyl protein thioesterase 1-deficient (Ppt1−/−) mice, a model of the infantile form of the diseases (CLN1). Therefore, we here explore whether pharmacological targeting of innate immune cells modifies disease outcome in CLN1 mice. Methods. We applied treatment with PLX3397 (150 ppm in the chow), a potent inhibitor of the colony stimulating factor-1 receptor (CSF-1R) to target innate immune cells in CLN1 mice. Experimental long-term treatment was non-invasively monitored by longitudinal optical coherence tomography and rotarod analysis, as well as analysis of visual acuity, myoclonic jerks, and survival. Treatment effects regarding neuroinflammation, neural damage, and neurodegeneration were subsequently analyzed by histology and immunohistochemistry. Results. We show that PLX3397 treatment attenuates neuroinflammation in CLN1 mice by depleting pro-inflammatory microglia/macrophages. This leads to a reduction of T lymphocyte recruitment, an amelioration of axon damage and neuron loss in the retinotectal system, as well as reduced thinning of the inner retina and total brain atrophy. Accordingly, long-term treatment with the inhibitor also ameliorates clinical outcomes in CLN1 mice, such as impaired motor coordination, visual acuity, and myoclonic jerks. However, we detected a sex- and region-biased efficacy of CSF-1R inhibition, with male microglia/macrophages showing higher responsiveness toward depletion, especially in the gray matter of the CNS. This results in a better treatment outcome in male Ppt1−/− mice regarding some histopathological and clinical readouts and reflects heterogeneity of innate immune reactions in the diseased CNS. Conclusions. Our results demonstrate a detrimental impact of innate immune reactions in the CNS of CLN1 mice. These findings provide insights into CLN pathogenesis and may guide in the design of immunomodulatory treatment strategies.