[Spatial Distribution, Risk, and Influencing Factors of River Water-Sediment Heavy Metals in the Lower Reaches of the Qianhe River].

The spatial distribution of heavy metals in rivers is affected by human activities and the natural environment, posing a risk to human health related to heavy metal pollution. In order to study the characteristics, health risk levels, and influencing factors of heavy metal distribution and pollution in the lower reaches of the Qianhe River, 19 surface sediments and 20 water samples were collected, and the contents of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn were measured by inductively coupled plasma mass spectrometry(ICP-MS). Using the DEM, air temperature, precipitation and other 11 factors as independent variables, the spatial differentiation of heavy metal pollution in sediments were explored based on geo-detector and geo-weighted regression model. The results showed that the eight heavy metal contents in the lower reaches of the Qianhe River did not exceed the "Surface Water Environmental Quality Standards" Ⅱ for water-like bodies, in which the variation coefficient of Pb element was 3.11, and the high content areas were mainly concentrated around Dongling Smelting Company and Fengxiang Railway Station. The average Rc value of adult carcinogens in water bodies was 7.72 E-06, showing a low risk level, and the children's carcinogens average Rc value was 1.17 E-04, showing a strong risk degree. The non-carcinogen risks for adults and children were both tolerable. The total high R value for children was mainly concentrated around Fengxiang Railway Station, posing a high risk. Sedimentation of heavy metals, except As and Mn, exceeded the soil background value in Shaanxi Province. The average content of Cd element was 1.12 mg·kg-1, which was 12 times the soil background value in Shaanxi Province. The pollution of Cd, Zn, and Pb was high, and distributed mainly in Changqing Village, Nanwan Village and Niujiatan Village, Gaozhuang, and Dongling Smelting Company. PLIzone of heavy metals in the sediments in the study area was 1.71, which was light pollution. DEM, temperature and precipitation were the main natural factors influencing the spatial pattern of heavy metal pollution load index(PLI) in sediments, and their nonlinear interactions were enhanced, which may play a role in the spread of heavy metals in sediments. This research can provide a scientific basis for urban planning and human health risks prevention in the Qianhe River.

Overexpression of P2X4 receptor in Schwann cells promotes motor and sensory functional recovery and remyelination via BDNF secretion after nerve injury.

Of the seven P2X receptor subtypes, P2X4 receptor (P2X4R) is widely distributed in the central nervous system, including in neurons, astrocytes, and microglia. Accumulating evidence supports roles for P2X4R in the central nervous system, including regulating cell excitability, synaptic transmission, and neuropathic pain. However, little information is available about the distribution and function of P2X4R in the peripheral nervous system. In this study, we find that P2X4R is mainly localized in the lysosomes of Schwann cells in the peripheral nervous system. In cultured Schwann cells, TNF-a not only enhances the synthesis of P2X4R protein but also promotes P2X4R trafficking to the surface of Schwann cells. TNF-a-induced BDNF secretion in Schwann cells is P2X4R dependent. in vivo experiments reveal that expression of P2X4R in Schwann cells of injured nerves is strikingly upregulated following nerve crush injury. Moreover, overexpression of P2X4R in Schwann cells by genetic manipulation promotes motor and sensory functional recovery and accelerates nerve remyelination via BDNF release following nerve injury. Our results suggest that enhancement of P2X4R expression in Schwann cells after nerve injury may be an effective approach to facilitate the regrowth and remyelination of injured nerves.

Rab27b is Involved in Lysosomal Exocytosis and Proteolipid Protein Trafficking in Oligodendrocytes.

Myelination by oligodendrocytes in the central nervous system requires coordinated exocytosis and endocytosis of the major myelin protein, proteolipid protein (PLP). Here, we demonstrated that a small GTPase, Rab27b, is involved in PLP trafficking in oligodendrocytes. We showed that PLP co-localized with Rab27b in late endosomes/lysosomes in oligodendrocytes. Short hairpin-mediated knockdown of Rab27b not only reduced lysosomal exocytosis but also greatly diminished the surface expression of PLP in oligodendrocytes. In addition, knockdown of Rab27b reduced the myelin-like membranes induced by co-culture of oligodendrocytes and neurons. Our data suggest that Rab27b is involved in myelin biogenesis by regulating PLP transport from late endosomes/lysosomes to the cell membrane in oligodendrocytes.

Rab27a/Slp2-a complex is involved in Schwann cell myelination.

Myelination of Schwann cells in the peripheral nervous system is an intricate process involving myelin protein trafficking. Recently, the role and mechanism of the endosomal/lysosomal system in myelin formation were emphasized. Our previous results demonstrated that a small GTPase Rab27a regulates lysosomal exocytosis and myelin protein trafficking in Schwann cells. In this present study, we established a dorsal root ganglion (DRG) neuron and Schwann cell co-culture model to identify the signals associated with Rab27a during myelination. First, Slp2-a, as the Rab27a effector, was endogenously expressed in Schwann cells. Second, Rab27a expression significantly increased during Schwann cell myelination. Finally, Rab27a and Slp2-a silencing in Schwann cells not only reduced myelin protein expression, but also impaired formation of myelin-like membranes in DRG neuron and Schwann cell co-cultures. Our findings suggest that the Rab27a/Slp2-a complex affects Schwann cell myelination in vitro.