Chuanjiang Lu

Acceleration of the Healing Process and Myocardial Regeneration May Be Important as a Mechanism of Improvement of Cardiac Function and Remodeling by Postinfarction Granulocyte Colony–Stimulating Factor Treatment

Background—We investigated whether the improvement of cardiac function and remodeling after myocardial infarction (MI) by granulocyte colony–stimulating factor (G-CSF) relates to acceleration of the healing process, in addition to myocardial regeneration. Methods and Results—In a 30-minute coronary occlusion and reperfusion rabbit model, saline (S) or 10 μg · kg−1 · d−1 of human recombinant G-CSF (G) was injected subcutaneously from 1 to 5 days after MI. Smaller left ventricular (LV) dimension, increased LV ejection fraction, and thicker infarct-LV wall were seen in G at 3 months after MI. At 2, 7, and 14 days and 3 months after MI, necrotic tissue areas were 14.2±1.5/13.4±1.1, 0.4±0.1/1.8±0.5*, 0/0, and 0/0 mm2 ·· slice−1 · kg−1, granulation areas 0/0, 4.0±0.7/8.5±1.0*, 3.9±0.8/5.7±0.7,* and 0/0 mm2 · slice−1 kg−1, and scar areas 0/0, 0/0, 0/0, and 4.2±0.5/7.9±0.9* mm2 slice−1 kg−1 in G and S, respectively (*P <0.05, G versus S). Clear increases of macrophages and of matrix metalloproteinases (MMP) 1 and 9 were seen in G at 7 days after MI. This suggests that G accelerates absorption of necrotic tissues via increase of macrophages and reduces granulation and scar tissues via expression of MMPs. Meanwhile, surviving myocardial tissue areas within the risk areas were significantly increased in G despite there being no difference in LV weight, LV wall area, or cardiomyocyte size between G and S. Confocal microscopy revealed significant increases of cardiomyocytes with positive 3,3,3′3′-tetramethylindocarbocyanine perchlorate and positive troponin I in G, suggesting enhanced myocardial regeneration by G. Conclusions—The acceleration of the healing process and myocardial regeneration may play an important role for the beneficial effect of post-MI G-CSF treatment.

Cilnidipine, an N+L-Type Dihydropyridine Ca Channel Blocker, Suppresses the Occurrence of Ischemia/Reperfusion Arrhythmia in a Rabbit Model of Myocardial Infarction

Dihydropyridine Ca channel blockers are widely prescribed for the treatment of hypertension and coronary artery diseases, but it remains unknown whether these agents protect against arrhythmias. We investigated whether cilnidipine, an N+L-type Ca channel blocker, reduces the incidences of ventricular premature beats (VPBs) and, if so, via what mechanisms. Japanese white rabbits underwent 30 min of ischemia and 48 h of reperfusion. Cilnidipine (0.5 or 1.0 μg/kg/min, i.v.) or saline (i.v.) was administered from 30 min before ischemia to 30 min after reperfusion. Electrocardiogram and blood pressure were monitored and the incidences of VPBs were measured. At 48 h after reperfusion, myocardial infarct was measured. Myocardial interstitial noradrenaline levels were determined before, during and after 30 min of ischemia with cilnidipine (0.5 and 1.0 μg/kg/min) or saline. The incidences of VPBs during ischemia and reperfusion were significantly attenuated in the cilnidipine 0.5 group (15.6±3.1 and 6.8±1.9 beats/30 min) and in the cilnidipine 1.0 group (10.4±4.9 and 3.5±1.0 beats/30 min) compared to the control group (27.2±4.5 and 24.2±3.1 beats/30 min), respectively. Myocardial interstitial noradrenaline levels were significantly reduced in the cilnidipine 0.5 and 1.0 groups compared to the control group during ischemia and reperfusion. The antiarrhythmic effect of cilnidipine may be related to the attenuation of cardiac sympathetic nerve activity. This finding may provide new insight into therapeutic strategies for hypertensive patients with ventricular arrhythmias.

Benidipine reduces myocardial infarct size involving reduction of hydroxyl radicals and production of protein kinase C-dependent nitric oxide in rabbits.

Japanese white rabbits underwent 30 minutes of ischemia and 48 hours of reperfusion. Benidipine (3 or 10 μg/kg, i.v.) was administered 10 minutes before ischemia with and without pretreatment with L-NAME (10 mg/kg, i.v., a NOS inhibitor), chelerythrine (5 mg/kg, i.v., a PKC blocker) or 5-HD (5 mg/kg, i.v. a mitochondrial KATP channel blocker), genistein (5 mg/kg, i.v. a protein tyrosin kinase blocker). SNAP (2.5 mg/kg/min × 70 minutes, i.v., an NO donor) was also administered 10 minutes before ischemia. Benidipine significantly reduced the infarct size in a dose-dependent manner (3 μg/kg: 29.0 ± 2.7%, n = 8, 10 μg/kg: 23.0 ± 2.4%, n = 10) compared with the control (41.6 ± 3.3%, n = 10). This effect was completely blocked by L-NAME (39.9 ± 3.6%, n = 8) and chelerythrine (35.5 ± 2.4%, n = 8) but not by 5-HD (23.0 ± 2.4%, n = 10) or genistein (24.6 ± 3.1%, n = 10). SNAP also reduced the infarct size (24.6 ± 3.1%, n = 8). Benidipine significantly increased the expression of eNOS mRNA at 30 minutes after reperfusion and significantly increased the expression of eNOS protein at 3 hours after reperfusion in the ischemic area of the left ventricle. Benidipine and SNAP significantly decreased myocardial interstitial 2,5-DHBA levels, an indicator of hydroxyl radicals, during ischemia and reperfusion. Benidipine increased myocardial interstitial NOx levels, which effect was blocked by chelerythrine, during 0 to 30 minutes and 150 to 180 minutes after reperfusion. Benidipine reduces the infarct size through PKC-dependent production of nitric oxide and decreasing hydroxyl radicals but not through involving protein tyrosine kinase or mitochondrial KATP channels in rabbits.

Antidiabetic drug miglitol inhibits myocardial apoptosis involving decreased hydroxyl radical production and Bax expression in an ischaemia/reperfusion rabbit heart

We examined whether antidiabetic drug miglitol could reduce ischaemia/reperfusion‐induced myocardial apoptosis by attenuating production. Japanese white rabbits were subjected to 30‐min coronary occlusion followed by 4‐h reperfusion with miglitol (10 mg kg−1, i.v., n=20) or saline (n=20). The infarct area was determined by myoglobin staining, and the infarct size (IS) was expressed as a percentage of the area at risk. DNA fragmentation was assessed by TUNEL method and DNA ladder formation. The expression of Bcl‐XL and Bax was detected by immunohistochemical analysis and Western blot analysis. Myocardial interstitial 2,5‐DHBA levels, an indicator of hydroxyl radicals, were measured during 30‐min ischaemia and 30‐min reperfusion in the absence (n=10) or presence of miglitol (10 mg kg−1, i.v., n=10) using a microdialysis technique. The IS was significantly reduced in the miglitol group (22.4±3.4%, n=10) compared to the control group (52.8±3.5%, n=10). Miglitol significantly decreased the 2,5‐DHBA level during ischaemia and reperfusion and suppressed the incidence of TUNEL‐positive myocytes in the ischaemic region (from 10.7±3.4 to 4.1±3.0%) and the intensity of DNA ladder formation. Miglitol significantly decreased the incidence of Bax‐positive myocytes in the ischaemic region (7.4±1.7 vs 13.7±1.9% of the control) and significantly attenuated the upregulation of Bax protein in the ischaemic regions (from 179±17 to 90±12% of sham). There was no difference in the expression of Bcl‐XL between the two groups. These data suggest that miglitol reduces myocardial apoptosis by attenuating production of hydroxyl radicals and suppressing the upregulation of the expression of Bax protein.

Autologous bone marrow cell transplantation improves left ventricular function in rabbit hearts with cardiomyopathy via myocardial regeneration-unrelated mechanisms

Recent studies suggest transplanted bone marrow cells (BMCs) can be used to reconstitute coronary vessels and myocardium following acute myocardial infarction, thereby improving cardiac function. We sought to investigate the therapeutic potential of BMC transplantation in the treatment of nonischemic cardiomyopathy. Experimental cardiomyopathy was produced by treating rabbits for 8 weeks with doxorubicin (2 mg/kg per week). Two weeks after the treatment was finished, freshly aspirated BMCs or an equivalent volume of phosphate-buffered saline was injected directly into the left ventricular free wall. Four weeks later, heart function was examined during perfusion on a Langendorff apparatus. Left ventricular developed pressure and ±dp/dt were significantly better in the transplantation group, among which echocardiography also showed significantly better ejection fractions. In addition, left ventricular weights as a fraction of body weight and left ventricular wall thicknesses were both lower in rabbits transplanted with BMCs than in controls. Immunohistochemical analyses carried out 2 weeks after transplantation showed no new myocardium and a very small number of endothelial cells originating from BMCs. On the other hand, immunoblotting revealed upregulated expression of transforming growth factor-β1 and downregulated expression of matrix metalloproteinase-1 and tumor necrosis factor-α following BMC transplantation. In conclusion, autologous BMC transplantation into cardiomyopathic rabbit hearts ameliorates the decline in ventricular function without regenerating cardiomyocytes, most likely by altering expression of various cytokines.