Chemotherapy influences inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) activity on 3D breast cancer cell line

Multicellular tumor spheroids (MTS) are three-dimensional structural forms of tumors grown in vitro in the laboratory. In this study, the aim was to determine the regulation of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) expressions on MTS in response to treatment with the commonly used anti-cancer drugs Doxorubicin and Docetaxel. The spheroids were generated using the "liquid overlay" technique. The distribution of both iNOS and eNOS was detected using indirect immunohistochemistry, while the expression of both iNOS and eNOS was measured using Western blots. Additionally, S-phase analysis using 5-bromo-2'-deoxyuridine (BrdU) was done on the MTS after treatment with doxorubicin, docetaxel, and a combination of the two. The Griess method was used to measure nitric oxide (NO) production in the cells. An increase in iNOS immunoreactivity and a decrease in eNOS immunoreactivity were observed after doxorubicin treatment, when compared with the other groups. Furthermore, upregulation of iNOS and downregulation of eNOS were detected in doxorubicin-treated cells using Western blotting. Insignificant iNOS expression was observed in all of the groups, and it was particularly low in the control and drug combination groups. NO production was also found to be significantly high after docetaxel treatment, and cell proliferation decreased after doxorubicin treatment. In conclusion, chemotherapy influences NOS activity differently with the presence of different drugs. The results with iNOS show that doxorubicin is a more effective drug than docetaxel, and a drug combination may play a helpful role in the suppression of tumorigenicity and cancer metastasis. Interestingly, eNOS expression increased after the addition of both docetaxel and the drug combination, and it was found to negatively correlate with the histological grade of the tumor. Therefore, analyzing the expression of both iNOS and eNOS might be very useful for targeting the treatment of breast carcinoma and obtaining better information on prognosis.

Evaluation of the relationship between inducible nitric oxide synthase (iNOS) activity and effects of melatonin in experimental osteoporosis in the rat

Inducible nitric oxide synthase (iNOS) plays a critical role in the pathogenesis of osteoporosis. iNOS generates nitric oxide (NO), a free radical contributing to the imbalance between bone formation and resorption caused by estrogen depletion. Melatonin is the major product of the pineal gland which is known to diminish iNOS expression and NO production significantly. The aim of this study was to determine the distribution of iNOS and the amount of apoptotic cells after melatonin treatment in ovariectomized rats. Since previous studies have shown that constitution of bone formation is primarily sustained in nucleus pulposus and epiphyseal cartilage, experiments were carried out on nucleus pulposus and epiphyseal cartilage; additional quantitation of osteoblasts and osteoclasts were evaluated on vertebral area as well. Vertebral sections of ovariectomized rats were obtained from formalin-fixed and parafin-embedded blocks. iNOS expression and quantitation of apoptotic cells in nucleus pulposus and epiphyseal cartilage were evaluated using indirect immunoperoxidase and TUNEL techniques, respectively. The number of osteoclasts and osteoblasts in trabecular bone was determined using histomorphometry. Ovariectomy increased iNOS expression and the number of apoptotic cells in nucleus pulposus and epiphyseal cartilage, whereas a 4-week treatment with melatonin (10 mg/kg/day) resulted in the reduction of both effects. These data indicate that there is strong influence of melatonin application on expression of iNOS, apoptosis, osteoclast and osteoblast numbers after ovariectomy. In conclusion, melatonin besides its usual use as an antiaging hormone, may also be an effective hormone in treatment of bone changes in estrogen deficiency states.

Assessment of effects of pinealectomy and exogenous melatonin administration on rat sciatic nerve suture repair: an electrophysiological, electron microscopic, and immunohistochemical study

BACKGROUND

Collagen scar formation at the cut end of a nerve, an important problem in clinical practice for neurosurgeons in peripheral nerve surgery, obstructs sprouting of axons into appropriate distal fascicles, and thereby limits nerve regeneration. Researchers attempt to control collagen accumulation in the formation of neuroma by various physical and chemical methods, but these have yielded only limited functional success. This is the first experimental study investigating the effects of melatonin (MLT) on nerve repair and neuronal regeneration in rat sciatic nerve suture repair.

METHODS

The hypothesis that exogenous MLT administration may inhibit the formation of neuroma in peripheral nerve surgery was investigated in rat sciatic nerve model. In this study, a total of 80 rats were used for control groups (Groups Ia, Ib, IIa, and IId), MLT group (Group Ic), surgical pinealectomy (Px) groups (Groups IIb and IIc), and group of MLT treatment following Px procedure (Group IIe). All animals underwent a surgical intervention consisting of bilateral sciatic nerve section and primary suture repair. At 8 weeks after repair, the animals were killed following completion of recording of nerve action potentials (NAPs). Then, unilateral sciatic nerve specimens including the suture repair region were carefully removed and the excised segments were processed for electron microscopy examination. Afterwards, contralateral sciatic nerve specimens from two animals from each group were removed and stained for immunohistochemical analysis.

RESULTS

Results of morphometric analysis revealed that Px procedure caused an elevation of collagen content of the sciatic nerve and macroscopic neuroma formation, and that there was a statistically significant reduction in collagen content of the same region in pinealectomized animals treated with MLT (p<0.001). Accordingly, electrophysiological findings demonstrated that the stimulus intensities required to excite a NAP response were increased in surgical Px group, but the presence of a reduced threshold response was found in the group treated with MLT following Px procedure (p<0.01). Immunohistochemical staining for Type I collagen and Type III collagen was markedly more intense in the epineurium of animals after Px. Virtually no or only weak staining was observed in animals in control groups and the MLT treatment group. Results of immunohistochemical analysis revealed that surgical Px procedure caused a strong immunoreactivity for Type I collagen and Type III collagen in all connective tissue planes of the nerve, especially in the epineurium, and there was a statistically significant reduction in immunoreactivity of the repair region in animals receiving MLT treatment after Px procedure (p<0.001).

CONCLUSION

This study demonstrates that exogenous MLT administration significantly inhibits collagen accumulation in the formation of neuroma in the suture repair site and thereby improves nerve regeneration. From a clinical standpoint, the positive effect of MLT administration on neuroma formation and nerve regeneration seems a particularly attractive treatment option. Therefore, we believe that nerve repair with addition of MLT may be a worthwhile option in addition to other treatment modalities in case of MLT deficiency, such as aging. However, further experimental and clinical studies using functional analysis warranted to confirm this result in future.