A highly conserved host lipase deacylates oxidized phospholipids and ameliorates acute lung injury in mice

Oxidized phospholipids have diverse biological activities, many of which can be pathological, yet how they are inactivated in vivo is not fully understood. Here, we present evidence that a highly conserved host lipase, acyloxyacyl hydrolase (AOAH), can play a significant role in reducing the pro-inflammatory activities of two prominent products of phospholipid oxidation, 1-palmitoyl-2-glutaryl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine. AOAH removed the sn-2 and sn-1 acyl chains from both lipids and reduced their ability to induce macrophage inflammasome activation and cell death in vitro and acute lung injury in mice. In addition to transforming Gram-negative bacterial lipopolysaccharide from stimulus to inhibitor, its most studied activity, AOAH can inactivate these important danger-associated molecular pattern molecules and reduce tissue inflammation and injury.

Acyloxyacyl hydrolase is a host determinant of gut microbiome-mediated pelvic pain

Dysbiosis of gut microbiota is associated with many pathologies, yet host factors modulating microbiota remain unclear. Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating condition of chronic pelvic pain often with co-morbid urinary dysfunction and anxiety/depression, and recent studies find fecal dysbiosis in IC/BPS patients. We identified the locus encoding acyloxyacyl hydrolase, Aoah, as a modulator of pelvic pain severity in a murine IC/BPS model. AOAH-deficient mice spontaneously develop rodent correlates of pelvic pain, increased responses to induced pelvic pain models, voiding dysfunction, and anxious/depressive behaviors. Here, we report that AOAH-deficient mice exhibit dysbiosis of GI microbiota. AOAH-deficient mice exhibit an enlarged cecum, a phenotype long associated with germ-free rodents, and a "leaky gut" phenotype. AOAH-deficient ceca showed altered gene expression consistent with inflammation, Wnt signaling, and urologic disease. 16S sequencing of stool revealed altered microbiota in AOAH-deficient mice, and GC-MS identified altered metabolomes. Co-housing AOAH-deficient mice with wild type mice resulted in converged microbiota and altered predicted metagenomes. Co-housing also abrogated the pelvic pain phenotype of AOAH-deficient mice, which was corroborated by oral gavage of AOAH-deficient mice with stool slurry of wild type mice. Converged microbiota also alleviated comorbid anxiety-like behavior in AOAH-deficient mice. Oral gavage of AOAH-deficient mice with anaerobes cultured from IC/BPS stool resulted in exacerbation of pelvic allodynia. Together, these data indicate that AOAH is a host determinant of normal gut microbiota, and dysbiosis associated with AOAH deficiency contributes to pelvic pain. These findings suggest that the gut microbiome is a potential therapeutic target for IC/BPS.

Acyloxyacyl Hydrolase Modulates the Gut Microbiome Through Transcriptional Regulators of Corticotropin-Releasing Factor

ABSTRACTGut microbiome-host interactions play a crucial role in health and disease. Altered gut microbiome composition has been observed in patients with interstitial cystitis/bladder pain syndrome (IC/BPS), a disorder characterized by pelvic pain, voiding dysfunction, and often co-morbid with anxiety/depression. We recently showed that mice deficient for acyloxyacyl hydrolase (AOAH) mimic pelvic pain symptoms and comorbidities of IC/BPS and also exhibit gut dysbiosis. In addition, we previously identified that the conditional knockout (cKO) of two transcriptional regulators of the gene encoding corticotropin-releasing factor, Crf, that are downstream of AOAH, aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor-γ (PPARγ), alleviate anxiety/depressive and voiding phenotypes of AOAH-deficient mice. Here, we examined the effects of AhR and PPARγ in CRF-expressing cells on the dysbiosis of AOAH-deficiency. AOAH-deficient mice with cKO of PPARγ and AhR/PPARγ exhibited reduced pelvic allodynia compared to AOAH-deficient mice, suggesting a role for PPARγ in regulating pelvic pain. 16S rRNA sequencing of fecal stool from female AOAH-deficient mice with a cKO of AhR and/or PPARγ in CRF-expressing cells identified altered gut microbiota distinct from AOAH-deficient stool. The cKO of AhR and PPARγ showed improved cecum barrier function in females compared to AOAH-deficient mice, whereas males were primarily affected by PPARγ, suggesting sex differences in gut responses. Pair-wise comparison of microbiota also suggested sex differences in response to AOAH-deficiency and conditional knockout of AhR and PPARγ. Our findings suggest that the dysbiosis and leaky gut of AOAH deficiency is mediated by AhR and PPARγ in CRF-expressing cells and reveal a novel mechanism and therapeutic targets for pelvic pain.

Acyloxyacyl Hydrolase Regulates Microglia-Mediated Pelvic Pain Through Toll-Like Receptor-4

ABSTRACTInterstitial cystitis/bladder pain syndrome (IC/BPS) is a devastating condition of chronic pelvic pain and urinary dysfunction. We have shown that mice deficient for the lipase acyloxyacyl hydrolase (AOAH) develop pelvic allodynia and exhibit symptoms and comorbidities consistent with IC/BPS, as well as gut dysbiosis. Microglia are resident immune cells of the central nervous system (CNS) that respond to changes in the gut microbiome, and studies have linked microglial activation to neuropathic pain. Additionally, microglia express toll-like receptors (TLRs), including TLR4, which are activated by microbial components. We have previously shown that AOAH-deficient mice exhibit increased gut permeability, suggesting a possible mechanism of microglial TLR4 activation via translocation of microbial products across the intestinal barrier to the brain. Here, we assessed the role of AOAH and TLR4 in microglial activation and pelvic pain. AOAH immunoreactivity co-localized with the microglial marker P2YR12 but not astrocytes, suggesting a functional role for AOAH in microglia. Pharmacologic ablation of CNS microglia with PLX5622 resulted in decreased pelvic allodynia in AOAH-deficient mice and resurgence of pelvic pain upon drug washout. Aligned with microglial activation, we observed altered cytokine abundance in Aoah−/− cortex that was reduced in Aoah/Tlr4−/− cortex. Consistent with our hypothesis of TLR4 activation by gut microbes, we observed microbiome-dependent activation of cultured BV2 microglial cells. Skeletal analyses revealed that AOAH-deficient mice have an activated microglia morphology in brain regions associated with neuropathic pain, independent of TLR4. Compared to Aoah−/− mice, Aoah/Tlr4−/− mice exhibited decreased pelvic pain and microglial cytokine expression. Together, these findings demonstrate differential roles for AOAH and TLR4 in microglial activation and pelvic pain and thus identify novel therapeutic targets for IC/BPS.

Acyloxyacyl Hydrolase is a Host Determinant of Gut Microbiome-Mediated Pelvic Pain

ABSTRACTDysbiosis of gut microbiota is associated with many pathologies, yet host factors modulating microbiota remain unclear. Interstitial cystitis/bladder pain syndrome (IC/BPS or “IC”) is a debilitating condition of chronic pelvic pain often with co-morbid urinary dysfunction and anxiety/depression, and recent studies find fecal dysbiosis in IC/BPS patients. We previously identified the locus encoding acyloxyacyl hydrolase, Aoah, as a modulator of pelvic pain severity in a murine IC/BPS model. AOAH-deficient mice spontaneously develop rodent correlates of pelvic pain, increased responses to induced pelvic pain models, voiding dysfunction, and anxious/depressive behaviors. Here, we report that AOAH-deficient mice exhibit dysbiosis of GI microbiota. AOAH-deficient mice exhibit an enlarged cecum, a phenotype long associated with germ-free rodents, and reduced trans-epithelial electrical resistance consistent with a “leaky gut” phenotype. AOAH-deficient ceca showed altered gene expression consistent with inflammation, Wnt signaling, and urologic disease. 16S rRNA sequencing of stool revealed altered microbiota in AOAH-deficient mice, and GC-MS identified altered metabolomes. Co-housing AOAH-deficient mice with wild type mice resulted in converged microbiota and altered predicted metagenomes. Co-housing also abrogated the pelvic pain phenotype of AOAH-deficient mice, which was corroborated by oral gavage of AOAH-deficient mice with stool slurry of wild type mice. Converged microbiota also alleviated comorbid anxiety-like behavior in AOAH-deficient mice. Oral gavage of AOAH-deficient mice with anaerobes cultured from IC/BPS stool resulted in exacerbation of pelvic allodynia. Together, these data indicate that AOAH is a host determinant of normal gut microbiota, and the dysbiosis associated with AOAH deficiency contributes to pelvic pain. These findings suggest that the gut microbiome is a potential therapeutic target for IC/BPS.

Biochemical transformation of bacterial lipopolysaccharides by acyloxyacyl hydrolase reduces host injury and promotes recovery

Animals can sense the presence of microbes in their tissues and mobilize their own defenses by recognizing and responding to conserved microbial structures (often called microbe-associated molecular patterns (MAMPs)). Successful host defenses may kill the invaders, yet the host animal may fail to restore homeostasis if the stimulatory microbial structures are not silenced. Although mice have many mechanisms for limiting their responses to lipopolysaccharide (LPS), a major Gram-negative bacterial MAMP, a highly conserved host lipase is required to extinguish LPS sensing in tissues and restore homeostasis. We review recent progress in understanding how this enzyme, acyloxyacyl hydrolase (AOAH), transforms LPS from stimulus to inhibitor, reduces tissue injury and death from infection, prevents prolonged post-infection immunosuppression, and keeps stimulatory LPS from entering the bloodstream. We also discuss how AOAH may increase sensitivity to pulmonary allergens. Better appreciation of how host enzymes modify LPS and other MAMPs may help prevent tissue injury and hasten recovery from infection.