Assessing the Effects of Nicotinamide Mononucleotide Supplementation on Pulmonary Inflammation in Male Mice Subchronically Exposed to Ambient Particulate Matter

Pulmonary surfactant biogenesis blockage mediated polyhexamethylene guanidine disinfectant induced pulmonary fibrosis

The widespread use of disinfectants and inhalation exposure to aerosolized forms is closely associated with adverse health effects on the respiratory system and pulmonary fibrosis, but the mechanism remains unclear. Here, we investigated the time-course pulmonary fibrosis effects of polyhexamethylene guanidine (PHMG) disinfectant inhalation exposure and elucidated its underlying mechanism. Specifically, scRNA-seq analysis revealed an initial increase in epithelial cell numbers after 4 weeks of PHMG exposure during induced pulmonary fibrosis, followed by a subsequent decrease after 8 weeks of exposure. Mechanistically, PHMG disrupted autophagic flux leading to intracellular accumulation and blocked pulmonary surfactant biogenesis in alveolar type II epithelial (AT2) cells both in vitro and in vivo. Furthermore, intervention studies using metformin confirmed that autophagy dysfunction mediated the blockage of pulmonary surfactant biogenesis in AT2 cells, playing a pivotal role in PHMG-induced pulmonary fibrosis. Our elucidation of these toxicological mechanisms provides valuable insights into the pathogenesis of pulmonary fibrosis triggered by environmental PHMG exposure, thereby offering a promising therapeutic target for mitigating and treating PHMG-associated pulmonary fibrosis.

Spatial regulation of NMN supplementation on brain lipid metabolism upon subacute and sub-chronic PM exposure in C57BL/6 mice

BACKGROUND

Atmospheric particulate matter (PM) exposure-induced neuroinflammation is critical in mediating nervous system impairment. However, effective intervention is yet to be developed.

RESULTS

In this study, we examine the effect of β-nicotinamide mononucleotide (NMN) supplementation on nervous system damage upon PM exposure and the mechanism of spatial regulation of lipid metabolism. 120 C57BL/6 male mice were exposed to real ambient PM for 11 days (subacute) or 16 weeks (sub-chronic). NMN supplementation boosted the level of nicotinamide adenine dinucleotide (NAD+) in the mouse brain by 2.04 times. This augmentation effectively reduced neuroinflammation, as evidenced by a marked decrease in activated microglia levels across various brain regions, ranging from 29.29 to 85.96%. Whole brain lipidomics analysis revealed that NMN intervention resulted in an less increased levels of ceramide (Cer) and lysophospholipid in the brain following subacute PM exposure, and reversed triglyceride (TG) and glycerophospholipids (GP) following sub-chronic PM exposure, which conferred mice with anti-neuroinflammation response, improved immune function, and enhanced membrane stability. In addition, we demonstrated that the hippocampus and hypothalamus might be the most sensitive brain regions in response to PM exposure and NMN supplementation. Particularly, the alteration of TG (60:10, 56:2, 60:7), diacylglycerol (DG, 42:6), and lysophosphatidylcholine (LPC, 18:3) are the most profound, which correlated with the changes in functional annotation and perturbation of pathways including oxidative stress, inflammation, and membrane instability unveiled by spatial transcriptomic analysis.

CONCLUSIONS

This study demonstrates that NMN intervention effectively reduces neuroinflammation in the hippocampus and hypothalamus after PM exposure by modulating spatial lipid metabolism. Strategies targeting the improvement of lipid homeostasis may provide significant protection against brain injury associated with air pollutant exposure.

Mitochondrial dysfunction-associated alveolar epithelial senescence is involved in CdCl2-induced COPD-like lung injury

An earlier study found that respiratory cadmium chloride (CdCl2) exposure caused COPD-like lung injury. This study aimed to explore whether mitochondrial dysfunction-mediated alveolar epithelial senescence is involved in CdCl2-induced COPD-like lung injury. Adult C57BL/6 mice were exposed to CdCl2 (10 mg/L) aerosol for six months. Beta-galactosidase-positive cells, p21 and p16 were increased in CdCl2-exposed mouse lungs. The in vitro experiments showed that γ-H2AX was elevated in CdCl2-exposed alveolar epithelial cells. The cGAS-STING pathway was activated in CdCl2-exposed alveolar epithelial cells and mouse lungs. Cxcl1, Cxcl9, Il-10, Il-1β and Mmp2, several senescence-associated secretory phenotypes (SASP), were upregulated in CdCl2-exposed alveolar epithelial cells. Mechanistically, CdCl2 exposure caused SIRT3 reduction and mitochondrial dysfunction in mouse lungs and alveolar epithelial cells. The in vitro experiment found that Sirt3 overexpression attenuated CdCl2-induced alveolar epithelial senescence and SASP. The in vivo experiments showed that Sirt3 gene knockout exacerbated CdCl2-induced alveolar epithelial senescence, alveolar structure damage, airway inflammation and pulmonary function decline. NMN, an NAD+ precursor, attenuated CdCl2-induced alveolar epithelial senescence and SASP in mouse lungs. Moreover, NMN supplementation prevented CdCl2-induced COPD-like alveolar structure damage, epithelial-mesenchymal transition and pulmonary function decline. These results suggest that mitochondrial dysfunction-associated alveolar epithelial senescence is involved in CdCl2-induced COPD-like lung injury.

Traffic-related ultrafine particles impair mitochondrial functions in human olfactory mucosa cells - Implications for Alzheimer's disease

Constituents of air pollution, the ultrafine particles (UFP) with a diameter of ≤0.1 μm, are considerably related to traffic emissions. Several studies link air pollution to Alzheimer's disease (AD), yet the exact relationship between the two remains poorly understood. Mitochondria are known targets of environmental toxicants, and their dysfunction is associated with neurodegenerative diseases. The olfactory mucosa (OM), located at the rooftop of the nasal cavity, is directly exposed to the environment and in contact with the brain. Mounting evidence suggests that the UFPs can impact the brain directly through the olfactory tract. By using primary human OM cultures established from nasal biopsies of cognitively healthy controls and individuals diagnosed with AD, we aimed to decipher the effects of traffic-related UFPs on mitochondria. The UFP samples were collected from the exhausts of a modern heavy-duty diesel engine (HDE) without aftertreatment systems, run with renewable diesel (A0) and petroleum diesel (A20), and from an engine of a 2019 model diesel passenger car (DI-E6d) equipped with state-of-the-art aftertreatment devices and run with renewable diesel (Euro6). OM cells were exposed to three different UFPs for 24-h and 72-h, after which cellular processes were assessed on the functional and transcriptomic levels. Our results show that UFPs impair mitochondrial functions in primary human OM cells by hampering oxidative phosphorylation (OXPHOS) and redox balance, and the responses of AD cells differ from cognitively healthy controls. RNA-Seq and IPA® revealed inhibition of OXPHOS and mitochondrial dysfunction in response to UFPs A0 and A20. Functional validation confirmed that A0 and A20 impair cellular respiration, decrease ATP levels, and disturb redox balance by altering NAD and glutathione metabolism, leading to increased ROS and oxidative stress. RNA-Seq and functional assessment revealed the presence of AD-related alterations in human OM cells and that different fuels and engine technologies elicit differential effects.

Gas6-Axl signal promotes indoor VOCs exposure-induced pulmonary fibrosis via pulmonary microvascular endothelial cells-fibroblasts cross-talk

Volatile organic compounds (VOCs) as environmental pollutants were associated with respiratory diseases. Pulmonary fibrosis (PF) was characterized by an increase of extracellular matrix, leading to deterioration of lung function. The adverse effects on lung and the potential mechanism underlying VOCs induced PF had not been elucidated clearly. In this study, the indoor VOCs exposure mouse model along with an ex vivo biosensor assay was established. Based on scRNA-seq analysis, the adverse effects on lung and potential molecular mechanism were studied. Herein, the results showed that VOCs exposure from indoor decoration contributed to decreased lung function and facilitated pulmonary fibrosis in mice. Then, the whole lung cell atlas after VOCs exposure and the heterogeneity of fibroblasts were revealed. We explored the molecular interactions among various pulmonary cells, suggesting that endothelial cells contributed to fibroblasts activation in response to VOCs exposure. Mechanistically, pulmonary microvascular endothelial cells (MPVECs) secreted Gas6 after VOCs-induced PANoptosis phenotype, bound to the Axl in fibroblasts, and then activated fibroblasts. Moreover, Atf3 as the key gene negatively regulated PANoptosis phenotype to ameliorate fibrosis induced by VOCs exposure. These novel findings provided a new perspective about MPVECs could serve as the initiating factor of PF induced by VOCs exposure.

The role of nicotinamide adenine dinucleotide salvage enzymes in cardioprotection

The increasing trend of cardiac diseases is becoming a major threat globally. Cardiac activities are based on integrated action potential through electronic flux changes within intra- and extracellular molecular activities. Nicotinamide adenine dinucleotide (NAD) is a major electron carrier present in almost all living cells and creates gated potential by electron exchange from one chemical to another in terms of oxidation (NAD+) and reduction (NADH) reactions. NAD+ plays an important role directly or indirectly in protecting against various cardiovascular diseases, including heart failure, occlusion, ischemia-reperfusion (IR) injury, arrhythmia, myocardial infarction (MI), rhythmic disorder, and a higher order of cardiovascular complexity. Nicotinamide phosphoribosyl transferase (NAMPT) is well known as a rate-limiting enzyme in this pathway except for de-novo NAD synthesis and directly involved in the cardioprotective activity. There are two more enzymes - nicotinate phosphoribosyl transferase (NAPRT) and nicotinamide riboside kinase (NRK) - which also work as rate-limiting factors in the NAD+ synthesis pathway. This study concentrated on the role of NAMPT, NAPRT, and NRK in cardioprotective activity and prospective cardiac health.

The Role of Nicotinamide Mononucleotide Supplementation in Psoriasis Treatment

Psoriasis is one of several chronic inflammatory skin diseases with a high rate of recurrence, and its pathogenesis remains unclear. Nicotinamide mononucleotide (NMN), as an important precursor of nicotinamide adenine dinucleotide (NAD+), has been reported to be a promising agent in treating various diseases, its positive effects including those induced via its anti-inflammatory and antioxidant properties. For this reason, we have aimed to explore the possible role of NMN in the treatment of psoriasis. Psoriasis models were constructed with imiquimod (IMQ) stimulation for 5 days in vivo and with M5 treatment in keratinocyte cell lines in vitro. NMN treatment during the IMQ application period markedly attenuated excess epidermal proliferation, splenomegaly, and inflammatory responses. According to GEO databases, Sirtuin1 (SIRT1) levels significantly decreased in psoriasis patients' lesion tissues; this was also the case in the IMQ-treated mice, while NMN treatment reversed the SIRT1 decline in the mouse model. Moreover, NMN supplementation also improved the prognoses of the mice after IMQ stimulation, compared to the untreated group with elevated SIRT1 levels. In HEKa and HaCaT cells, the co-culturing of NMN and M5 significantly decreased the expression levels of proinflammation factors, the phosphorylation of NF-κB, stimulator of interferon genes (STING) levels, and reactive oxygen species levels. NMN treatment also recovered the decrease in mitochondrial membrane potential and respiration ability and reduced mtDNA in the cytoplasm, leading to the inhibition of autoimmune inflammation. The knockdown of SIRT1 in vitro eliminated the protective and therapeutic effects of NMN against M5. To conclude, our results indicate that NMN protects against IMQ-induced psoriatic inflammation, oxidative stress, and mitochondrial dysfunction by activating the SIRT1 pathway.