The spread of COVID-19 has greatly threatened human health and economic growth. Angiotensin-converting enzyme 2 (ACE2) is a receptor for severe acute respiratory syndrome coronavirus 2 (SARS-COV-2). By attaching to ACE2, SARS-COV-2 reduces its expression and induces lung injury. Vitamin D can inhibit the progression of COVID-19 by inhibiting the activity of ROCK pathway, up-regulating ACE2 expression and bio-availability, and slowing down the adverse reactions caused by Ang II accumulation. This study explored a novel mechanism, i.e., vitamin D protects against COVID-19-induced injury by upregulating ACE2 expression. It provides theoretical guidance for the role of Vitamin D in the prevention and treatment of COVID-19.

ObjectiveTo observe the effects of Cuscutae Semen on the learning and memory ability， N6-methyladenosine （m⁶A）-related modification enzymes and total m⁶A level in hippocampus of the offspring of fear-damaged pregnant rats. MethodForty-five pregnant rats were randomly divided into blank group， model group and Cuscutae Semen group. From the 1^st day to the 19^th day of pregnancy， rats in the model group and the Cuscutae Semen group were induced by observing electric shock of other rats. The Cuscutae Semen group was treated with 5 g·kg^-1·d^-1 Cuscutae Semen decoction （ig）， while the other two groups were treated with the same amount of purified water. The offspring were assigned following the grouping method of their maternal generation. The behavioral changes of the offspring were tested by Morris water maze on 21^st day after birth， and the development of hippocampal neurons was observed by transmission electron microscopy. The mRNA and protein expression levels of methyltransferase-like 3 （METTL3）， METTL14， Wilms tumor 1 associated protein （WTAP）， fat mass and obesity-associated protein （FTO） and Alk B homologue 5 （ALKBH5） were detected by Real-time polymerase chain reaction （Real-time PCR）， Western blot and immunohistochemistry （IHC）. The total content of m⁶A in hippocampus was determined by high performance liquid chromatography tandem mass spectrometry （LC-MS/MS）. ResultCompared with the conditions in the blank group， the average latency duration in the model group was prolonged， and the number of entries in the target quadrant， the target quadrant duration and the number of crossing the platform were decreased （P<0.01）. Additionally， the model group had seriously damaged structure of hippocampal CA1 and CA3 neurons， swollen mitochondria， expanded endoplasmic reticulum， and small number of synapses with some having blurred structure， and the expression levels of METTL3， METTL14， FTO， ALKBH5 as well as the total m⁶A level were lower than those in the blank group （P<0.05，P<0.01）. Compared with the model group， the Cuscutae Semen group had shortened average latency duration， increased number of entries in the target quadrant， target quadrant duration and number of crossing the platform （P<0.01）， alleviated damage of hippocampal CA1 and CA3 neurons， fine structure of mitochondrial and endoplasmic reticulum， and clear， intact and dense synapses. And the expression levels of METTL3， METTL14， FTO as well as the total level of m⁶A were up regulated， while the expression level of ALKBH5 was down regulated in the Cuscutae Semen group （P<0.05，P<0.01）. ConclusionCuscutae Semen improved the learning and memory ability of the offspring of the rats affected by fear damaging kidney during pregnancy， protected hippocampal neurons， and up-regulated the expression levels of METTL3， METTL14， FTO and the total m⁶A level in hippocampus.