Effects of Melatonin on Neurobehavior and Cognition in a Cerebral Palsy Model of plppr5−/− Mice

Abstract

Cerebral palsy (CP), a group of clinical syndromes caused by non-progressive brain damage in the developing fetus or infant, is one of the most common causes of lifelong physical disability in children in most countries. At present, many researchers believe that perinatal cerebral hypoxic ischemic injury or inflammatory injury are the main causes of cerebral palsy. Previous studies including our works confirmed that melatonin has a protective effect against convulsive brain damage during development and that it affects the expression of various molecules involved in processes such as metabolism, plasticity and signaling in the brain. Integral membrane protein plppr5 is a new member of the plasticity-related protein family, which is specifically expressed in brain and spinal cord, and induces filopodia formation as well as neurite growth. It is highly expressed in the brain, especially in areas of high plasticity, such as the hippocampus. The signals are slightly lower in the cortex, the cerebellum, and in striatum. Noteworthy, during development plppr5 mRNA is expressed in the spinal cord, i.e., in neuron rich regions such as in medial motor nuclei, suggesting that plppr5 plays an important role in the regulation of neurons. However, the existing literature only states that plppr5 is involved in the occurrence and stability of dendritic spines, and research on its possible involvement in neonatal ischemic hypoxic encephalopathy has not been previously reported. We used plppr5 knockout (plppr5−/−) mice and their wild-type littermates to establish a model of hypoxicischemic brain injury (HI) to further explore the effects of melatonin on brain injury and the role of plppr5 in this treatment in an HI model, which mainly focuses on cognition, exercise, learning, and memory. All the tests were performed at 3–4 weeks after HI. As for melatonin treatment, which was performed 5 min after HI injury and followed by every 24h. In these experiments, we found that there was a significant interaction between genotype and treatment in novel object recognition tests, surface righting reflex tests and forelimb suspension reflex tests, which represent learning and memory, motor function and coordination, and the forelimb grip of the mice, respectively. However, a significant main effect of genotype and treatment on performance in all behavioral tests were observed. Specifically, wild-type mice with HI injury performed better than plppr5−/− mice, regardless of treatment with melatonin or vehicle. Moreover, treatment with melatonin could improve behavior in the tests for wild-type mice with HI injury, but not for plppr5−/− mice. This study showed that plppr5 knockout aggravated HI damage and partially weakened the neuroprotection of melatonin in some aspects (such as novel object recognition test and partial nerve reflexes), which deserves further study.

Underlying causes of cerebral palsy: public health perspectives

“…Experimental analysis indicates that wild-type mice having hypoxic-ischaemic brain injury show better performance as compared to PLPPR5-/-mice, irrespective of melatonin treatment. Moreover, melatonin treatment improves behaviour in the tests for wild-type animal models with hypoxic-ischaemic brain injuries, but not for PLPPR5-/-mice [44].…”

“…Interestingly, studies have shown that perinatal cerebral hypoxic ischaemic injuries as well as inflammatory injuries are the main causes of cerebral palsy. PLPPR5 is an integral membrane molecule of the plasticity-related family of proteins [44]. It is expressed specifically in spinal cord as well as brain and drives the growth of the neurites.…”

Melatonin for Neonatal Encephalopathy: From Bench to Bedside

“…Thirteen studies [ 60 , 62 , 71 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 ] report improvement in histological outcomes including reduction in infarct volume, reduction in markers of apoptosis, necrosis, cell death, astrocytosis, and microgliosis. Neurobehavioral studies were also reported in 3 studies [ 62 , 132 , 140 ], observing improved cognitive performance, learning and memory, motor function, and co-ordination. Berger et al (2019) [ 141 ] reported no overall long-term treatment effect based on brain injury volume, diffusion tensor imaging, histology and functional outcomes however the variability of injury in this model was large.…”

PRG5 Knockout Precipitates Late-Onset Hypersusceptibility to Pilocarpine-Induced Juvenile Seizures by Exacerbating Hippocampal Zinc Signaling-Mediated Mitochondrial Damage

“…Then, Cas9 and gRNA were injected into fertilized mouse eggs at the same time (see Table 1 for the sequence information for gRNA). The Cas9 protein binds to the target site under the guidance of gRNA, causing DNA double-strand breaks, resulting in the deletion of the base sequence of the target site and ultimately achieving systemic gene knockout (Sun et al, 2021). The strain backgrounds of PRG5 knockout mice and WT wild-type mice are both C57BL/6JNju (see Table 2 for strain information of knockout mice).…”

“…To identify whether the PRG5 protein is knocked out in KO mice, we first cut 3-5 mm tail tip tissue from the offspring mice born at the age of 3 days, and used PCR to perform genotype identification, and compare the size of the DNA products of the mice to be identified: Wildtype mice (PRG5 −/− ) = 439 bp, homozygous PRG5 knockout mice (PRG5 −/− ) = 414 bp, heterozygous PRG5 knockout mice (PRG5 ±) = 414 bp + 439 bp. (The process was completed by the Nanjing Institute of Biomedicine, Nanjing University) (Sun et al, 2021).…”