High-resolution mapping of sensory fibers at the healthy and post-myocardial infarct whole transgenic hearts

The sensory nervous system is critical to maintain cardiac function. As opposed to efferent innervation, less is known about cardiac afferents. For this, we mapped the VGLUT2-expressing cardiac afferent fibers of spinal and vagal origin by using the VGLUT2::tdTomato double transgenic mouse as an approach to visualize the whole hearts both at the dorsal and ventral sides. For comparison, we colabeled mixed-sex transgenic hearts with either TUJ1 protein for global cardiac innervation or tyrosine hydroxylase for the sympathetic network at the healthy state or following ischemic injury. Interestingly, the nerve density for global and VGLUT2-expressing afferents was found significantly higher on the dorsal side compared to the ventral side. From the global nerve innervation detected by TUJ1 immunoreactivity, VGLUT2 afferent innervation was detected to be 15-25% of the total network. The detailed characterization of both the atria and the ventricles revealed a remarkable diversity of spinal afferent nerve ending morphologies of flower sprays, intramuscular endings, and end-net branches that innervate distinct anatomical parts of the heart. Using this integrative approach in a chronic myocardial infarct model, we showed a significant increase in hyperinnervation in the form of axonal sprouts for cardiac afferents at the infarct border zone, as well as denervation at distal sites of the ischemic area. The functional and physiological consequences of the abnormal sensory innervation remodeling post-ischemic injury should be further evaluated in future studies regarding their potential contribution to cardiac dysfunction.

Anatomical characterization of vagal nodose afferent innervation and ending morphologies at the murine heart using a transgenic approach

Heart is an extensively innervated organ and its function is strictly coordinated by autonomic neural circuits. After pathological events such as myocardial infarction (MI), cardiac nerves undergo a structural and functional remodeling contributing to cardiac dysfunction. Although the efferent component of the cardiac nerves has been well described, sensory innervation of the heart has not been defined in detail. Considering its importance, comprehensive description of vagal afferent innervation on the whole heart would enable a better description of autonomic imbalances manifesting as sympathoexcitation and vagal withdrawal in post-ischemic states. To address this issue, we globally mapped the vagal nodose afferent fibers innervating the whole murine heart with unprecedented resolution. By using the Phox2b-Cre::tdTomato transgenic mouse line, we described the detailed distribution and distinct vagal sensory ending morphologies at both the dorsal and ventral sides of the mouse heart. By neural tracing analysis, we quantitated the distribution and prevalence of vagal afferent nerve fibers with varying diameters across dorsal and ventral surfaces of the heart. Moreover, we demonstrated that vagal afferents formed flower spray and end-net-like endings within the atria and ventricles. As distinct from the atria, vagal afferents formed intramuscular array-like endings within the ventricles. Furthermore, we showed that vagal afferents undergo structural remodeling by forming axonal sprouts around the infarct area in post-MI hearts. These findings improve our understanding of the potential effect of vagal afferent remodeling on autonomic imbalance and generation of cardiac arrhythmias and could prospectively contribute to the development of more effective neuromodulatory therapies.

Evaluation of oxidative stress biomarkers and antioxidant parameters in allergic asthma patients with different level of asthma control

OBJECTIVE

There is evidence that reactive oxygen species, especially free radicals, produced during the immune and inflammatory response may play important roles in the development of asthma.We aimed to evaluate the levels of certain oxidative stress biomarkers and antioxidant capacity in asthma patients with different asthma control levels in comparison to healthy subjects.

METHODS

A total of 120 adult allergic asthma patients and 120 healthy individuals were included in this study. Using spectrophotometric methods, we analyzed two oxidative stress markers, levels of malondialdehyde (MDA) and protein carbonyls (PC), as well as reduced glutathione (GSH), total antioxidant capacity (FRAP) and catalase activity as critical antioxidant defense parameters in the blood samples of allergic asthma patients and healthy controls. The patients were divided into 3 subgroups according to asthma control test (ACT) results: totally controlled (TCG), partially controlled (PCG) and uncontrolled (UCG) subgroups. All biomarkers were compared between the three patient subgroups, as well as between total asthma patients and control subjects.

RESULTS

There were remarkable differences between the control group and the combined patient group for all parameters. A significant increase in MDA and PC, especially in the UCG (p < 0.01 and p < 0.05, respectively) was detected in comparison to other subgroups. Additionally, increased MDA and PC levels, as well as decreased GSH levels were observed in all subgroups individually in comparison to the control (p < 0.001).

CONCLUSIONS

This research demonstrates the presence of severe oxidative stress, considering the increase in lipid peroxidation and protein oxidation, in patients with allergic asthma, even under controlled conditions.