A Pilot Study to Examine the Effect of Chronic Treatment with Immunosuppressive Drugs on Mucociliary Clearance in a Vagotomized Murine Model

Abstract

BackgroundPreviously, we have demonstrated that mucociliary clearance (MCC) is diminished within the first months after surgery in lung transplant patients and the explanation for the reduction in MCC is unknown. We hypothesized that chronic treatment with a commonly prescribed regimen of immunosuppressive drugs significantly impairs MCC. We tested this hypothesis in a murine model of lung transplantation.MethodsFifteen C57BL/6 mice underwent vagotomy on the right side to simulate denervation associated with lung transplantation in humans. For 6 days, seven mice (controls) were intraperitoneally injected with three 100 µL doses of phosphate buffered saline and eight mice (immunosuppressed) were injected with three 100 µL injections of tacrolimus (1 mg/kg), mycophenolate mofetil (30 mg/kg), and prednisone (2 mg/kg) once daily. Then, mice inhaled the radioisotope 99mtechnetium and underwent gamma camera imaging of their lungs for 6.5 hrs. Counts in the right lung at 1–1.5 hrs and at 6–6.5 hrs were first background-corrected and then decay-corrected to time 0 counts. Decay-corrected counts were then divided by time 0 counts. Retention at each time point was subtracted from 1.00 and multiplied by 100% to obtain percent removed by mucociliary clearance.ResultsAlthough there was a slowing of MCC at 1–1.5 hrs for the immunosuppressed mice, there was no statistical difference in MCC measured at 1–1.5 hrs for the two groups of mice. At 6–6.5 hrs, MCC was significantly slower in the immunosuppressed mice, compared to controls, with 7.78±5.9% cleared versus 23.01±11.7% cleared, respectively (p = 0.006).ConclusionsThese preliminary results suggest that chronic treatment with immunosuppressive medications significantly slows MCC in vagotomized C57BL/6 mice. These findings could shed light on why MCC is reduced in lung transplant patients whose lungs are denervated during surgery and who are chronically treated with immunosuppressive drugs post surgery.

Histone deacetylase 6–mediated selective autophagy regulates COPD-associated cilia dysfunction

“…MCC was quantified using a noninvasive oropharyngeal aspiration procedure described previously (56,87,88), with minor modifications as described in the Supplemental Methods. Briefly, mice were anesthetized, and 50 μl of normal saline containing approximately 0.3-0.5 mCi of 99m Tc-sc was introduced into the distal part of the oropharynx and aspirated.…”

Acute and chronicin vivoeffects of exposure to nicotine and propylene glycol from an E-cigarette on mucociliary clearance in a murine model

“…Approximately, 16–18 hours following the last E- cigarette exposure, mice were anesthetized by intraperitoneal injection of ketamine (100 μg/g) and xylazine (16 μg/g) and suspended from their upper incisors by suture material at a 45° incline. With the tongue extended, mice aspirated one 50 μl aliquot of the radioisotope technetium-labeled sulfur colloid ( 99m Tc-SC) aerosol, as described previously (Bhashyam et al, 2010, 2012; McGrath-Morrow et al, 2006). Each aliquot contained 60–80 μCi of the isotope, but no nicotine, or PG.…”

Cilia and Mucociliary Clearance

“…While this method provides a direct measurement of MCC, it is not well suited for routine experimental studies. Various methods have been used to study MCC in many different animal models, including sheep, dogs, pigs, and mice (Sabater et al 1999; Foster et al 2001; Lay et al 2003; Bhashyam et al 2012; Hoegger et al 2014). The use of genetically modified mouse models has provided a valuable tool to study the role of motile cilia, however, the small size of the mouse airways has made measurements of in vivo clearance rates using radioactivity challenging (Foster et al 2001; Bhashyam et al 2012).…”

“…Various methods have been used to study MCC in many different animal models, including sheep, dogs, pigs, and mice (Sabater et al 1999; Foster et al 2001; Lay et al 2003; Bhashyam et al 2012; Hoegger et al 2014). The use of genetically modified mouse models has provided a valuable tool to study the role of motile cilia, however, the small size of the mouse airways has made measurements of in vivo clearance rates using radioactivity challenging (Foster et al 2001; Bhashyam et al 2012). Other investigators studying mouse models have recorded the movement of fluorescent particles along the trachea or nasopharynx of the mouse (e.g., Ostrowski et al 2010) or measured the recovery of fluorescent beads from the lungs after a specified time (Look et al 2001; Grubb et al 2016).…”