The MRL Model: A Valuable Tool in Studies of Autoimmunity-Brain Interactions

Cognitive dysfunction in SLE: An understudied clinical manifestation

Neuropsychiatric lupus (NPSLE) is a debilitating manifestation of SLE which occurs in a majority of SLE patients and has a variety of clinical manifestations. In the central nervous system, NPSLE may result from ischemia or penetration of inflammatory mediators and neurotoxic antibodies through the blood brain barrier (BBB). Here we focus on cognitive dysfunction (CD) as an NPSLE manifestation; it is common, underdiagnosed, and without specific therapy. For a very long time, clinicians ignored cognitive dysfunction and researchers who might be interested in the question struggled to find an approach to understanding mechanisms for this manifestation. Recent years, however, propelled by a more patient-centric approach to disease, have seen remarkable progress in our understanding of CD pathogenesis. This has been enabled through the use of novel imaging modalities and numerous mouse models. Overall, these studies point to a pivotal role of an impaired BBB and microglial activation in leading to neuronal injury. These insights suggest potential therapeutic modalities and make possible clinical trials for cognitive impairment.

A novel mouse model for checkpoint inhibitor-induced adverse events

Immune checkpoint inhibitors have demonstrated significant efficacy in the treatment of a variety of cancers, however their therapeutic potential is limited by abstruse immune related adverse events. Currently, no robust animal model exists of checkpoint inhibitor-induced adverse events. Establishing such a model will improve our mechanistic understanding of this process, which in turn will inform design of improved therapies. We developed a mouse model to determine inflammatory toxicities in response to dual checkpoint blockade in the presence of syngeneic tumors. Mice from susceptible genetic backgrounds received intraperitoneal injections of anti-mouse PD-1 and CTLA-4 antibodies. The mice were monitored for weight loss and histologic evidence of inflammation. Blood was collected for basic metabolic panels and titers of anti-nuclear antibodies. In parallel, mice were also treated with prednisolone, which is commonly used to treat immune related adverse events among cancer patients. Among all the genetic backgrounds, B6/lpr mice treated with anti-CTLA-4 and anti-PD-1 antibodies developed more substantial hepatitis, pancreatitis, colitis, and pneumonitis characterized by organ infiltration of immune cells. Mice that developed tissue infiltration demonstrated high serum levels of glucose and high titers of anti-nuclear antibodies. Finally, while administration of prednisolone prevented the development of the inflammatory adverse events, it also abrogated the protective anti-tumor effect of the checkout inhibitors. Genetic background and treatment modalities jointly modified the inflammatory adverse events in tumor bearing mice, suggesting a complex mechanism for checkpoint inhibitor-related inflammation. Future studies will assess additional genetic susceptibility factors and will examine possible contributions from the administration of other anti-inflammatory drugs.

Analysis of brain metabolites by gas chromatography-mass spectrometry reveals the risk-benefit concerns of prednisone in MRL/lpr lupus mice

OBJECTIVE

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a common cause of disability in systemic lupus erythematosus (SLE). This study aims to investigate the metabolic changes in the hypothalamus and frontal cortex in lupus-prone MRL/lpr mice.

METHODS

Metabolic changes were analyzed using gas chromatography-mass spectrometry (GC-MS).

RESULTS

According to the principal component analysis (PCA), the metabolic profiles were different between the frontal cortex and hypothalamus, but they were comparable between MRL/lpr and MRL/MpJ mice (16 weeks of age). By OPLS-DA, eight cortical and six hypothalamic differential metabolites were identified in MRL/lpr as compared to MRL/MpJ mice. Among these differential metabolites, we found a decrease of N-acetyl-L-aspartate (NAA, a potential marker of neuronal integrity), an increase of pyruvate and a decrease of glutamate in the frontal cortex but not in the hypothalamus. Prednisone treatment (3 mg/kg from 8 weeks of age) relieved the decrease of NAA but further increased the accumulation of pyruvate in the frontal cortex, additionally affected eight enriched pathways in the hypothalamus, and led to significant imbalances between the excitation and inhibition in both the frontal cortex and hypothalamus.

CONCLUSION

These results suggest that the frontal cortex may be more preferentially affected than the hypothalamus in SLE. Prednisone disrupted rather than relieved metabolic abnormalities in the brain, especially in the hypothalamus, indicating that the risk-benefit balance of prednisone for SLE or NPSLE remains to be further evaluated.