Simulated Microgravity Impairs Human NK Cell Cytotoxic Activity Against Space Radiation-Relevant Leukemic Cells.

Natural killer (NK) cells are important effectors of the innate immune system. Unlike T cells, NK cells do not require antigen-priming, making them an important first-line of defense against malignant cells. Because of the potential for increased cancer risk as a result of astronaut exposure to space radiation, we performed studies to determine whether conditions of microgravity present during spaceflight affects the body's natural defenses against leukemogenesis. Human NK cells were cultured for 48 hours under normal gravity and simulated microgravity (sµG), and cytotoxicity against K-562 (CML) and MOLT-4 (T-ALL) cell lines was measured using standard methodology or under continuous conditions of sµG. Even this brief exposure to sµG markedly reduced NK cytotoxicity against both leukemic cells using standard assay procedures, and these deleterious effects were even more pronounced in continuous sµG. RNA-seq performed on NK cells from two healthy donors provided insight into the mechanism(s) by which sµG reduced cytotoxicity. Given our prior report that human HSC exposed to simulated space radiation gave rise to T-ALL in vivo , the reduced cytotoxicity against MOLT-4 is striking and raises the possibility that µG may add to astronaut risk of leukemogenesis during prolonged missions beyond LEO.

Small-Fiber Polyneuropathy Is Prevalent in Patients With Interstitial Cystitis/Bladder Pain Syndrome.

IMPORTANCE: The pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS) is imperfectly understood. Recent studies reported that small-fiber polyneuropathy (SFPN) is common in fibromyalgia, a condition commonly comorbid with IC/BPS. OBJECTIVE: The objective of this study was to determine the prevalence of SFPN in a large cohort of IC/BPS patients. METHODS: Adults diagnosed with IC/BPS scheduled to undergo either therapeutic hydrodistention (n = 97) or cystectomy with urinary diversion (n = 3) were prospectively recruited to this study. A skin biopsy obtained from the lower leg was used for intraepidermal nerve fiber density measurement. Small-fiber polyneuropathy (+/-) status was determined by comparing linear intraepidermal nerve fiber density (fibers/mm2) with normative reference values. Demographic information, medical history, and diagnoses for 14 conditions (both urologic and nonurologic) known to co-occur with IC/BPS were documented from self-report and electronic medical record. RESULTS: In this large cohort of patients with IC/BPS, 31% (31/100) were positive for SFPN. Intraepidermal nerve fiber density was below the median for age and sex in 81% (81/100) of patients. Approximately one-third (31%) of SFPN+ patients reported co-occurring chronic fatigue syndrome, compared with 10.6% of the SFPN- group (P = 0.034). Small-fiber polyneuropathy-positive patients reported significantly fewer allergies than SFPN- patients (37.9% vs 60.6%; P = 0.047). There were no significant differences in bladder capacity or Hunner lesion status between the SFPN+ and SFPN- subgroups. CONCLUSIONS: Small-fiber polyneuropathy is a common finding in patients with IC/BPS, and SFPN status is significantly correlated with co-occurring chronic fatigue syndrome and negatively correlated with the presence of allergies in this population.

Small Fiber Polyneuropathy Is Associated With Non-Bladder-Centric Interstitial Cystitis/Bladder Pain Syndrome Patients.

OBJECTIVES: Interstitial cystitis/bladder pain syndrome (IC/BPS) comprises at least 2 phenotypes. Bladder centric patients typically demonstrate low bladder capacity (BC), often with Hunner lesion (HL), whereas non-bladder-centric patients typically have normal cystoscopic findings and more co-occurring nonurologic symptoms/syndromes (NUS), contributing to widespread pain beyond the bladder. Small fiber polyneuropathy (SFPN) is significantly associated with fibromyalgia, a frequent IC/BPS codiagnosis and may play an etiologic role in IC/BPS. We assessed SFPN status in bladder-centric versus non-bladder-centric IC/BPS patients. METHODS: Distal leg biopsies were obtained from 11 IC/BPS patients after therapeutic hydrodistention. Specimens were embedded/sectioned per standard protocol and stained for protein gene product 9.5, an intraepidermal nerve fiber marker. To determine SFPN status, intraepidermal nerve fiber density was calculated and compared with normative reference values stratified by age/sex. The SFPN prevalence and reported comorbidities were compared between low BC and/or HL-positive (bladder-centric) versus non-low BC, HL (non-bladder-centric) patients. RESULTS: Seven patients (63.6%) were SFPN positive. Non-bladder-centric patients demonstrated significantly more SFPN (6/7, 85.7%) compared with bladder-centric patients (1/4, 25.0%; P = 0.027). Non-bladder-centric patients also reported more comorbid NUS overall (1.25 ± 0.83 vs 5.86 ± 2.47; P = 0.003), including fibromyalgia (P = 0.010), migraines (P = 0.035), anxiety/panic disorder (P = 0.035), allergies (P = 0.027), and asthma (P = 0.035). CONCLUSIONS: In this pilot study, SFPN was significantly more common in non-bladder-centric IC/BPS, that is, those patients who also reported greater prevalence of NUS, including fibromyalgia, migraines, anxiety/panic disorders, allergies, and asthma. These findings suggest that SFPN may have an etiologic role in a larger, systemic pain syndrome and should be explored further.

Very Low Density Lipoprotein Assembly Is Required for cAMP-responsive Element-binding Protein H Processing and Hepatic Apolipoprotein A-IV Expression.

Hepatic apolipoprotein A-IV (apoA-IV) expression is correlated with hepatic triglyceride (TG) content in mouse models of chronic hepatosteatosis, and steatosis-induced hepatic apoA-IV gene expression is regulated by nuclear transcription factor cAMP-responsive element-binding protein H (CREBH) processing. To define what aspects of TG homeostasis regulate hepatic CREBH processing and apoA-IV gene expression, several mouse models of attenuated VLDL particle assembly were subjected to acute hepatosteatosis induced by an overnight fast or short term ketogenic diet feeding. Compared with chow-fed C57BL/6 mice, fasted or ketogenic diet-fed mice displayed increased hepatic TG content, which was highly correlated (r2 = 0.95) with apoA-IV gene expression, and secretion of larger, TG-enriched VLDL, despite a lower rate of TG secretion and a similar or reduced rate of apoB100 secretion. When VLDL particle assembly and secretion was inhibited by hepatic shRNA-induced apoB silencing or genetic or pharmacologic reduction in microsomal triglyceride transfer protein (MTP) activity, hepatic TG content increased dramatically; however, CREBH processing and apoA-IV gene expression were attenuated compared with controls. Adenovirus-mediated reconstitution of MTP expression proportionately restored CREBH processing and apoA-IV expression in liver-specific MTP knock-out mice. These results reveal that hepatic TG content, per se, does not regulate CREBH processing. Instead, TG mobilization into the endoplasmic reticulum for nascent VLDL particle assembly activates CREBH processing and enhances apoA-IV gene expression in the setting of acute steatosis. We conclude that VLDL assembly and CREBH activation play key roles in the response to hepatic steatosis by up-regulating apoA-IV and promoting assembly and secretion of larger, more TG-enriched VLDL particles.

Impact of murine intestinal apolipoprotein A-IV expression on regional lipid absorption, gene expression, and growth.

Apolipoprotein A-IV (apoA-IV) is synthesized by intestinal enterocytes during lipid absorption and secreted into lymph on the surface of nascent chylomicrons. A compelling body of evidence supports a central role of apoA-IV in facilitating intestinal lipid absorption and in regulating satiety, yet a longstanding conundrum is that no abnormalities in fat absorption, feeding behavior, or weight gain were observed in chow-fed apoA-IV knockout (A4KO) mice. Herein we reevaluated the impact of apoA-IV expression in C57BL6 and A4KO mice fed a high-fat diet. Fat balance and lymph cannulation studies found no effect of intestinal apoA-IV gene expression on the efficiency of fatty acid absorption, but gut sac transport studies revealed that apoA-IV differentially modulates lipid transport and the number and size of secreted triglyceride-rich lipoproteins in different anatomic regions of the small bowel. ApoA-IV gene deletion increased expression of other genes involved in chylomicron assembly, impaired the ability of A4KO mice to gain weight and increase adipose tissue mass, and increased the distal gut hormone response to a high-fat diet. Together these findings suggest that apoA-IV may play a unique role in integrating feeding behavior, intestinal lipid absorption, and energy storage.